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Bernard TE, Wolf ST, Kenney WL. A Novel Conceptual Model for Human Heat Tolerance. Exerc Sport Sci Rev 2024; 52:39-46. [PMID: 38294236 PMCID: PMC10963138 DOI: 10.1249/jes.0000000000000332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Human "heat tolerance" has no accepted definition or physiological underpinnings; rather, it is almost always discussed in relative or comparative terms. We propose to use environmental limits to heat balance accounting for metabolic rate and clothing, that is, the environments for which heat stress becomes uncompensable for a specified metabolic rate and clothing, as a novel metric for quantifying heat tolerance.
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Affiliation(s)
- Thomas E. Bernard
- College of Public Health, University of South Florida, Tampa, FL 33612
| | - S. Tony Wolf
- Department of Kinesiology, University of Georgia, Athens, GA 30602
| | - W. Larry Kenney
- Department of Kinesiology and Integrative and Biomedical Physiology Program, The Pennsylvania State University, University Park, PA 16802
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Wolf ST. The Tour de France, but make it recreational: possible for mortals. J Appl Physiol (1985) 2024; 136:430-431. [PMID: 38205549 DOI: 10.1152/japplphysiol.00014.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 01/08/2024] [Indexed: 01/12/2024] Open
Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, University of Georgia, Athens, Georgia, United States
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Fisher KG, Cottle RM, Kenney WL, Wolf ST. Sunscreen does not alter sweating responses or critical environmental limits in young adults (PSU HEAT project). J Appl Physiol (1985) 2024; 136:322-329. [PMID: 38126091 DOI: 10.1152/japplphysiol.00756.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 11/27/2023] [Accepted: 12/13/2023] [Indexed: 12/23/2023] Open
Abstract
Outdoor athletes often eschew using sunscreen due to perceived performance impairments, which many attribute in part to the potential for reduced thermoregulatory heat loss. Past studies examining the impact of sunscreen on thermoregulation are equivocal. The purpose of this study was to determine the effects of mineral and chemical-based sunscreens on sweating responses and critical environmental limits in hot-dry (HD) and warm-humid (WH) environments. Nine subjects (3 M/6 F; 25 ± 2 yr) were tested with 1) no sunscreen (control), 2) chemical-, and 3) mineral-based sunscreen. Subjects were exposed to progressive heat stress with either 1) constant dry-bulb temperature (Tdb) at 34°C and increasing water vapor pressure (Pa) (WH trials) or 2) constant Pa at 12 mmHg and increasing Tdb (HD trials). Subjects walked at 4.9 ± 0.5 metabolic equivalents (METs) until an upward inflection in gastrointestinal temperature was observed (i.e., the critical environmental limit). Compared with control (39.9 ± 3.0°C), critical Tdb was not different in mineral (39.2 ± 3.5°C, P = 0.39) or chemical (39.7 ± 3.0°C, P = 0.98) sunscreen trials in HD environments. Compared with control (18.8 ± 4.0 mmHg), critical Pa was not different in mineral (18.9 ± 4.8 mmHg, P = 0.81) or chemical (19.5 ± 4.6 mmHg, P = 0.81) sunscreen trials in WH environments. Sweating rates, evaporative heat loss, skin wettedness, and sweating efficiency were not different among the three trials in the WH (all P ≥ 0.48) or HD (all P ≥ 0.87) environments. Critical environmental limits are unaffected by sunscreen application, suggesting sunscreen does not alter integrative thermoregulatory responses during exercise in the heat.NEW & NOTEWORTHY Our findings demonstrate that neither sweating nor critical environmental limits were affected by mineral-based and chemical-based sunscreen applications. The rates of change in core temperature during compensable and uncompensable heat stress were not changed by wearing sunscreen. Evaporative heat loss, efficiency of sweat evaporation, skin wettedness, and sweating rates were unaffected by sunscreen. Sunscreen did not alter integrative thermoregulatory responses during exercise in the heat.
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Affiliation(s)
- Kat G Fisher
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Rachel M Cottle
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania, United States
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
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Tony Wolf S, Cottle RM, Fisher KG, Vecellio DJ, Larry Kenney W. Heat stress vulnerability and critical environmental limits for older adults. Commun Earth Environ 2023; 4:486. [PMID: 38293008 PMCID: PMC10826365 DOI: 10.1038/s43247-023-01159-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 12/05/2023] [Indexed: 02/01/2024]
Abstract
The present study examined heat stress vulnerability of apparently healthy older vs. young adults and characterized critical environmental limits for older adults in an indoor setting at rest (Rest) and during minimal activity associated with activities of daily living. Critical environmental limits are combinations of ambient temperature and humidity above which heat balance cannot be maintained (i.e., becomes uncompensable) for a given metabolic heat production. Here we exposed fifty-one young (23±4 yrs) and 49 older (71±6 yrs) adults to progressive heat stress across a wide range of environments in an environmental chamber during Minimal Activity (young and older subjects) and Rest (older adults only). Heat compensability curves were shifted leftward for older adults indicating age-dependent heat vulnerablity (p < 0.01). During Minimal Activity, critical environmental limits were lower in older compared to young adults (p < 0.0001) and lower than those at Rest (p < 0.0001). These data document heat vulnerability of apparently healthy older adults and to define critical environmental limits for indoor settings in older adults at rest and during activities of daily living, and can be used to develop evidence-based recommendations to minimize the deleterious impacts of extreme heat events in this population.
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Affiliation(s)
- S. Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802 USA
| | - Rachel M. Cottle
- Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802 USA
- Center for Healthy Aging, The Pennsylvania State University, University Park, PA 16802 USA
| | - Kat G. Fisher
- Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802 USA
| | - Daniel J. Vecellio
- Center for Healthy Aging, The Pennsylvania State University, University Park, PA 16802 USA
| | - W. Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802 USA
- Center for Healthy Aging, The Pennsylvania State University, University Park, PA 16802 USA
- Graduate Program in Physiology, The Pennsylvania State University, University Park, PA 16802 USA
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Bernard TE, Ashley CD, Wolf ST, Odera AM, Lopez RM, Kenney WL. Distribution of upper limit of the prescriptive zone values for acclimatized and unacclimatized individuals. J Appl Physiol (1985) 2023; 135:601-608. [PMID: 37498291 PMCID: PMC10538976 DOI: 10.1152/japplphysiol.00724.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 06/27/2023] [Accepted: 07/18/2023] [Indexed: 07/28/2023] Open
Abstract
Heat stress has an adverse impact on worker health and well-being, and the effects will increase with more frequent and severe heat events associated with global warming. Acclimatization to heat stress is widely considered to be a critical mitigation strategy and wet bulb globe temperature- (WBGT-) based occupational standards and guidelines contain adjustments for acclimatization. The purpose here was to 1) compare the mean values for the upper limit of the prescriptive zone (ULPZ, below which the rise in core temperature is minimal) between unacclimatized and acclimatized men and women; 2) demonstrate that the change in the occupational exposure limit (ΔOEL) due to acclimatization is independent of metabolic rate; 3) examine the relation between ΔOEL and body surface area (BSA); and 4) compare the exposure-response curves between unacclimatized and acclimatized populations. Empirically derived ULPZ data for unacclimatized participants from Pennsylvania State University (PSU) and acclimatized participants from University of South Florida (USF) were used to explore the difference between unacclimatized and acclimatized heat exposure limits. The findings provide support for a constant 3°C WBGT OEL decrease to account for unacclimatized workers. Body surface area explained part of the difference in ULPZ values between men and women. In addition, the pooled PSU and USF data provide insight into the distribution of individual values for the ULPZ among young, healthy unacclimatized and acclimatized populations in support of occupational heat stress guidelines.NEW & NOTEWORTHY Occupational exposure limit guidelines using wet bulb globe temperature (WBGT) distinguish between acclimatized and unacclimatized workers with about a 3°C difference between them. For the first time, empirical data from two laboratories provide support for acclimatization state adjustments. Using a constant difference rather than increasing differences with metabolic rate better describes the limit for unacclimatized participants. Furthermore, the lower upper limit of the prescriptive zone (ULPZ) values set forth for women do not relate to fitness level but are partly explained by their smaller body surface area (BSA). An examination of individual ULPZ values suggests that many unacclimatized individuals should be able to sustain safe work at the exposure limit for acclimatized workers.
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Affiliation(s)
- Thomas E Bernard
- College of Public Health, University of South Florida, Tampa, Florida, United States
| | - Candi D Ashley
- Exercise Science Program, College of Education, University of South Florida, Tampa, Florida, United States
| | - S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Ayub M Odera
- College of Public Health, University of South Florida, Tampa, Florida, United States
| | - Rebecca M Lopez
- School of Physical Therapy & Rehabilitation Sciences, Department of Orthopaedics & Sports Medicine, University of South Florida, Tampa, Florida, United States
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States
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Bernard TE, Ashley CD, Wolf ST, Kenney WL. Core temperature and heart rate at the upper limit of the prescriptive zone. Physiol Rep 2023; 11:e15812. [PMID: 37688426 PMCID: PMC10492005 DOI: 10.14814/phy2.15812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 08/18/2023] [Accepted: 08/18/2023] [Indexed: 09/10/2023] Open
Abstract
The expressed goal of limiting workplace heat stress exposures to a core temperature (Tc ) of 38°C traces back to a 1969 World Health Organization Technical Report (WHO Series 412). The actual goal was to limit exposures to the upper limit of the prescriptive zone (ULPZ). To explore the physiological strain at the ULPZ, progressive heat stress protocol data from Penn State University (PSU) and University of South Florida (USF) below and at the ULPZ were used to articulate the relation of Tc and heart rate (HR) to metabolic rate (MR) with consideration of acclimatization state, clothing, exposure condition (PreULPZ vs. ULPZ), and sex. Regression models demonstrated the association of MR and sex with Tc and HR. At the ULPZ, women had systematically higher values of Tc and HR than men at the same MR likely due to higher relative demands. There was no effect for acclimatization state and clothing. As expected for individuals, Tc was practically constant below the ULPZ and HR exhibited increasing values approaching the ULPZ. At 490 W, the high MR cited in the WHO document, the mean Tc for men was near the 38°C limit with systematically lower Tc at lower MRs.
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Affiliation(s)
| | - Candi D. Ashley
- Exercise Science Program, College of EducationUniversity of South FloridaTampaFLUSA
| | - S. Tony Wolf
- Department of KinesiologyThe Pennsylvania State UniversityUniversity ParkPAUSA
- Present address:
Department of KinesiologyUniversity of GeorgiaAthensGAUSA
| | - W. Larry Kenney
- Department of KinesiologyThe Pennsylvania State UniversityUniversity ParkPAUSA
- Graduate Program in PhysiologyThe Pennsylvania State UniversityUniversity ParkPAUSA
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Cottle RM, Fisher KG, Wolf ST, Kenney WL. Onset of Cardiovascular Drift during Progressive Heat Stress in Young Adults (PSU HEAT Project). J Appl Physiol (1985) 2023. [PMID: 37348014 PMCID: PMC10393325 DOI: 10.1152/japplphysiol.00222.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 06/21/2023] [Indexed: 06/24/2023] Open
Abstract
With climate change, humans are at greater risk for heat-related morbidity and mortality, often secondary to increased cardiovascular strain associated with an elevated core temperature (Tc). Critical environmental limits (i.e., the upper limits of compensable heat stress) have been established based on Tc responses for healthy, young individuals. However, specific environmental limits for the maintenance of cardiovascular homeostasis have not been investigated in the context of thermal strain during light activity. Therefore, the purposes of this study were to (1) identify the specific environmental conditions (combinations of ambient temperature and water vapor pressure) at which cardiovascular drift (i.e., a continuous rise in heart rate (HR)) began to occur and (2) compare those environments to the environmental limits for the maintenance of heat balance. Fifty-one subjects (27F;23±4yrs) were exposed to progressive heat stress across a wide range of environmental conditions in an environmental chamber at two low metabolic rates reflecting minimal activity (MinAct;159±34W) or light ambulation (LightAmb;260±55W). Whether systematically increasing ambient temperature or humidity, the onset of cardiovascular drift occurred at lower environmental conditions compared with Tc inflection points at both light intensities (P<0.05). Further, the time at which cardiovascular drift began preceded the time of Tc inflection (MinAct P=0.005; LightAmb P=0.0002), and the difference in time between HR and Tc inflection points did not differ across environmental conditions for either exercise intensity (MinAct P=0.08; LightAmb P=0.06). These data suggest that even in young adults, increases in cardiovascular strain precede the point at which heat stress becomes uncompensable during light activity.
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Affiliation(s)
- Rachel M Cottle
- Department of Kinesiology, Pennsylvania State University, Univeristy Park, PA, United States
- Center for Healthy Aging, College of Health and Human Development, Pennsylvania State University, University Park, Pennsylvania, United States
| | - Kat G Fisher
- Department of Kinesiology, Pennsylvania State University, Univeristy Park, PA, United States
| | - S Tony Wolf
- Department of Kinesiology, Pennsylvania State University, Univeristy Park, PA, United States
| | - W Larry Kenney
- Department of Kinesiology, Pennsylvania State University, Univeristy Park, PA, United States
- Center for Healthy Aging, College of Health and Human Development, Pennsylvania State University, University Park, Pennsylvania, United States
- Graduate Program in Physiology, Pennsylvania State University, University Park, PA, United States
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Dillon GA, Wolf ST, Williams AC, Kenney WL, Alexander LM. Nitric oxide-mediated cutaneous microvascular function is not altered in middle-aged-to-older adults following mild SARS-CoV-2 infection: A pilot study. Physiol Rep 2023; 11:e15704. [PMID: 37269174 DOI: 10.14814/phy2.15704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 03/28/2023] [Indexed: 06/04/2023] Open
Abstract
We tested the hypothesis that post-COVID-19 adults (PC) would have impaired cutaneous nitric oxide (NO)-mediated vasodilation compared to controls (CON). We performed a cross-sectional study including 10 (10 F/0 M, 69 ± 7 years) CON and 7 (2 F/5 M, 66 ± 8 years) PC (223 ± 154 days post-diagnosis). COVID-19 symptoms severity (survey) was assessed (0-100 scale for 18 common symptoms). NO-dependent cutaneous vasodilation was induced by a standardized 42°C local heating protocol and quantified via perfusion of 15 mM NG-nitro-L-arginine methyl ester during the plateau of the heating response (intradermal microdialysis). Red blood cell flux was measured with laser-Doppler flowmetry. Cutaneous vascular conductance (CVC = flux/mm Hg) was presented as a percentage of maximum (28 mM sodium nitroprusside +43°C). All data are means ± SD. The local heating plateau (CON: 71 ± 23% CVCmax vs. PC: 81 ± 16% CVCmax , p = 0.77) and NO-dependent vasodilation (CON: 56 ± 23% vs. PC: 60 ± 22%, p = 0.77) were not different between groups. In the PC group neither time since diagnosis nor peak symptom severity (46 ± 18 AU) correlated with NO-dependent vasodilation (r < 0.01, p = 0.99 and r = 0.42, p = 0.35, respectively). In conclusion, middle-aged and older adults who have had COVID-19 did not have impaired NO-dependent cutaneous vasodilation. Additionally, in this cohort of PC, neither time since diagnosis nor symptomology were related to microvascular function.
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Affiliation(s)
- Gabrielle A Dillon
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
- Center for Healthy Aging, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - S Tony Wolf
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
| | - Auni C Williams
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
| | - W Larry Kenney
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
- Center for Healthy Aging, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
| | - Lacy M Alexander
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
- Center for Healthy Aging, The Pennsylvania State University, University Park, State College, Pennsylvania, USA
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Wolf ST, Havenith G, Kenney WL. Relatively minor influence of individual characteristics on critical wet-bulb globe temperature (WBGT) limits during light activity in young adults (PSU HEAT Project). J Appl Physiol (1985) 2023; 134:1216-1223. [PMID: 36995912 PMCID: PMC10211460 DOI: 10.1152/japplphysiol.00657.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 03/22/2023] [Accepted: 03/23/2023] [Indexed: 03/31/2023] Open
Abstract
Critical environmental limits are temperature-humidity thresholds above which heat balance cannot be maintained for a given metabolic heat production. This study examined the association between individual characteristics [sex, body surface area (AD), aerobic capacity (V̇o2max), and body mass (mb)] and critical environmental limits in young adults at low metabolic rates. Forty-four (20 M/24 F; 23 ± 4 yr) subjects were exposed to progressive heat stress in an environmental chamber at two low net metabolic rates (Mnet); minimal activity (MinAct; Mnet = ∼160 W) and light ambulation (LightAmb; Mnet = ∼260 W). In two hot-dry (HD; ≤25% rh) environments, ambient water vapor pressure (Pa = 12 or 16 mmHg) was held constant and dry-bulb temperature (Tdb) was systematically increased. In two warm-humid (WH; ≥50% rh) environments, Tdb was held constant at 34°C or 36°C, and Pa was systematically increased. The critical wet-bulb globe temperature (WBGTcrit) was determined for each condition. During MinAct, after entry of Mnet into the forward stepwise linear regression model, no individual characteristics were entered into the model for WH (R2adj = 0.01, P = 0.27) or HD environments (R2adj = -0.01, P = 0.44). During LightAmb, only mb was entered into the model for WH environments (R2adj = 0.44, P < 0.001), whereas only V̇o2max was entered for HD environments (R2adj = 0.22; P = 0.002). These data demonstrate negligible importance of individual characteristics on WBGTcrit during low-intensity nonweight-bearing (MinAct) activity with a modest impact of mb and V̇o2max during weight-bearing (LightAmb) activity in extreme thermal environments.NEW & NOTEWORTHY Our laboratory has recently published a series of papers establishing the upper ambient temperature-humidity thresholds for maintaining heat balance, termed critical environmental limits, in young adults. However, no studies have investigated the relative influence of individual characteristics, such as sex, body size, and aerobic fitness, on those environmental limits. Here, we demonstrate the contributions of sex, body mass, body surface area, and maximal aerobic capacity on critical wet-bulb globe temperature (WBGT) limits in young adults.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - George Havenith
- Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough, United Kingdom
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, United States
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States
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Fisher KG, Kenney WL, Wolf ST. Within-limb Variation in Skin Pigmentation Does Not Influence Cutaneous Vasodilation. J Appl Physiol (1985) 2023; 134:1403-1408. [PMID: 37078502 DOI: 10.1152/japplphysiol.00118.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023] Open
Abstract
Ultraviolet radiation (UVR) exposure acutely reduces nitric oxide (NO)-dependent cutaneous vasodilation. Additionally, increased constitutive skin melanin is associated with attenuated NO-dependent cutaneous vasodilation. However, the impact of within-limb variation in skin melanization, associated with seasonal UVR exposure, on NO-dependent cutaneous vasodilation is unknown. We investigated the effect of within-limb variation in skin melanin on NO-dependent cutaneous vasodilation. Intradermal microdialysis fibers were placed in the inner-upper arm, ventral forearm, and dorsal forearm of seven adults (33±14 yrs; 4M/3F) with light constitutive skin pigmentation. Melanin-index (M-index; an index of skin pigmentation), measured via reflectance spectrophotometry, confirmed differences in sun exposure among sites. A standardized local heating (42°C) protocol induced cutaneous vasodilation. After attaining a stable elevated blood flow plateau, 15mM NG-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor) was infused to quantify the NO contribution. Laser-Doppler flowmetry (LDF) measured red cell flux and cutaneous vascular conductance (CVC=LDF/mean arterial pressure) and was normalized to maximal (%CVCmax; 28mM sodium nitroprusside + 43°C local heating). Dorsal forearm M-index was higher (50.5±11.8 a.u.) compared to the ventral forearm (37.5±7.4 a.u.; p≤0.03) and upper arm (30.0±4.0 a.u.; p≤0.001). Cutaneous vasodilation responses to local heating were not different among sites (p≥0.12). Importantly, neither the magnitude of the local heating plateau (dorsal: 85±21%; ventral: 70±21%; upper: 87±15%; p≥0.16) nor the NO-mediated component of that response (dorsal: 59±15%; ventral: 54±13%; upper: 55±11%; p≥0.79) were different among sites. These data suggest that within-limb differences in skin pigmentation secondary to seasonal UVR exposure do not alter NO-dependent cutaneous vasodilation.
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Affiliation(s)
- Kat G Fisher
- Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania, United States
| | - W Larry Kenney
- Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania, United States
- Graduate Program in Physiology, Pennsylvania State University, University Park, Pennsylvania, United States
| | - S Tony Wolf
- Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania, United States
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Wolf ST, Vecellio DJ, Kenney WL. Adverse heat-health outcomes and critical environmental limits (Pennsylvania State University Human Environmental Age Thresholds project). Am J Hum Biol 2023; 35:e23801. [PMID: 36125292 PMCID: PMC9840654 DOI: 10.1002/ajhb.23801] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/24/2022] [Accepted: 07/29/2022] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The earth's climate is warming and the frequency, duration, and severity of heat waves are increasing. Meanwhile, the world's population is rapidly aging. Epidemiological data demonstrate exponentially greater increases in morbidity and mortality during heat waves in adults ≥65 years. Laboratory data substantiate the mechanistic underpinnings of age-associated differences in thermoregulatory function. However, the specific combinations of environmental conditions (i.e., ambient temperature and absolute/relative humidity) above which older adults are at increased risk of heat-related morbidity and mortality are less clear. METHODS This review was conducted to (1) examine the recent (past 3 years) literature regarding heat-related morbidity and mortality in the elderly and discuss projections of future heat-related morbidity and mortality based on climate model data, and (2) detail the background and unique methodology of our ongoing laboratory-based projects aimed toward identifying the specific environmental conditions that result in elevated risk of heat illness in older adults, and the implications of using the data toward the development of evidence-based safety interventions in a continually-warming climate (PSU HEAT; Human Environmental Age Thresholds). RESULTS The recent literature demonstrates that extreme heat continues to be increasingly detrimental to the health of the elderly and that this is apparent across the world, although the specific environmental conditions above which older adults are at increased risk of heat-related morbidity and mortality remain unclear. CONCLUSION Characterizing the environmental conditions above which risk of heat-related illnesses increase remains critical to enact policy decisions and mitigation efforts to protect vulnerable people during extreme heat events.
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Affiliation(s)
- S. Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, 16802
| | - Daniel J. Vecellio
- Center for Healthy Aging, The Pennsylvania State University, University Park, PA, 16802
| | - W. Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, 16802
- Center for Healthy Aging, The Pennsylvania State University, University Park, PA, 16802
- Graduate Program in Physiology, The Pennsylvania State University, University Park, PA, 16802
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Vecellio DJ, Wolf ST, Cottle RM, Kenney WL. Correction to: Utility of the Heat Index in defining the upper limits of thermal balance during light physical activity (PSU HEAT Project). Int J Biometeorol 2022; 66:2567-2568. [PMID: 36269448 PMCID: PMC9684221 DOI: 10.1007/s00484-022-02384-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Affiliation(s)
- Daniel J Vecellio
- Center for Health Aging, College of Health and Human Development, Pennsylvania State University, 422 Biobehavioral Health Building, University Park, PA, 16802, USA.
| | - S Tony Wolf
- Department of Kinesiology, Pennsylvania State University, University Park, PA, 16802, USA
| | - Rachel M Cottle
- Department of Kinesiology, Pennsylvania State University, University Park, PA, 16802, USA
| | - W Larry Kenney
- Center for Health Aging, College of Health and Human Development, Pennsylvania State University, 422 Biobehavioral Health Building, University Park, PA, 16802, USA
- Department of Kinesiology, Pennsylvania State University, University Park, PA, 16802, USA
- Graduate Program in Physiology, Pennsylvania State University, University Park, PA, 16802, USA
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Cottle RM, Lichter ZS, Vecellio DJ, Wolf ST, Kenney WL. Core temperature responses to compensable versus uncompensable heat stress in young adults (PSU HEAT Project). J Appl Physiol (1985) 2022; 133:1011-1018. [PMID: 36049058 PMCID: PMC9550570 DOI: 10.1152/japplphysiol.00388.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/11/2022] [Accepted: 08/26/2022] [Indexed: 11/22/2022] Open
Abstract
With global warming, much attention has been paid to the upper limits of human adaptability. However, the time to reach a generally accepted core temperature criterion (40.2°C) associated with heat-related illness above (uncompensable heat stress) and just below (compensable heat stress) the upper limits for heat balance remains unclear. Forty-eight (22 men/26 women; 23 ± 4 yr) subjects were exposed to progressive heat stress in an environmental chamber during minimal activity (MinAct, 159 ± 34 W) and light ambulation (LightAmb, 260 ± 55 W) in warm-humid (WH; ∼35°C, >60% RH) and hot-dry (HD; 43°C-48°C, <25% RH) environments until heat stress became uncompensable. For each condition, we compared heat storage (S) and the change in gastrointestinal temperature (ΔTgi) over time during compensable and uncompensable heat stress. In addition, we examined whether individual characteristics or seasonality were associated with the rate of increase in Tgi. During compensable heat stress, S was higher in HD than in WH environments (P < 0.05) resulting in a greater but more variable ΔTgi (P ≥ 0.06) for both metabolic rates. There were no differences among conditions during uncompensable heat stress (all P > 0.05). There was no influence of sex, aerobic fitness, or seasonality, but a larger body size was associated with a greater ΔTgi during LightAmb in WH (P = 0.003). The slopes of the Tgi response during compensable (WH: MinAct, 0.06, LightAmb, 0.09; HD: MinAct, 0.12, LightAmb, 0.15°C/h) and uncompensable (WH: MinAct, 0.74, LightAmb, 0.87; HD: MinAct, 0.71, LightAmb, 0.93°C/h) heat stress can be used to estimate the time to reach a target core temperature from any given starting value.NEW & NOTEWORTHY This study is the first to examine heat storage and the rate of change in core temperature above (uncompensable heat stress) and just below (compensable heat stress) critical environmental limits to human heat balance. Furthermore, we examine the influence of individual subject characteristics and seasonality on the change in core temperature in warm-humid versus hot-dry environments. We provide the rate of change in core temperature, enabling projections to be made to and from any hypothetical core temperature.
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Affiliation(s)
- Rachel M Cottle
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Center for Healthy Aging, College of Health and Human Development, The Pennsylvania State University, University Park, Pennsylvania
| | - Zachary S Lichter
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Daniel J Vecellio
- Center for Healthy Aging, College of Health and Human Development, The Pennsylvania State University, University Park, Pennsylvania
| | - S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Center for Healthy Aging, College of Health and Human Development, The Pennsylvania State University, University Park, Pennsylvania
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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14
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Wolf ST, Dillon GA, Alexander LM, Jablonski NG, Kenney WL. Skin pigmentation is negatively associated with circulating vitamin D concentration and cutaneous microvascular endothelial function. Am J Physiol Heart Circ Physiol 2022; 323:490-498. [PMID: 35930446 PMCID: PMC9448272 DOI: 10.1152/ajpheart.00309.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/22/2022]
Abstract
Darkly pigmented individuals are at the greatest risk of hypovitaminosis D, which may result in microvascular endothelial dysfunction via reduced nitric oxide (NO) bioavailability and/or increased oxidative stress and inflammation. We investigated the associations among skin pigmentation (M-index; skin reflectance spectrophotometry), serum vitamin D concentration [25(OH)D], circulating inflammatory cytokine (TNF-α, IL-6, and IL-10) concentrations, and the NO contribution to local heating-induced cutaneous vasodilation (%NO-mediated vasodilation) in a diversely pigmented cohort of young adults. An intradermal microdialysis fiber was placed in the forearms of 33 healthy adults (14 men/19 women; 18-27 yr; M-index, 30-81 AU) for local delivery of pharmacological agents. Lactated Ringer's solution was perfused through the fiber during local heating-induced (39°C) cutaneous vasodilation. After attaining stable elevated blood flow, 15 mM NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibiter) was infused to quantify %NO-mediated vasodilation. Red cell flux was measured (laser-Doppler flowmetry; LDF) and cutaneous vascular conductance (CVC = LDF/MAP) was normalized to maximal (%CVCmax; 28 mM sodium nitroprusside + 43°C). Serum [25(OH)D] and circulating cytokines were analyzed by ELISA and multiplex assay, respectively. M-index was negatively associated with [25(OH)D] (r = -0.57, P < 0.0001) and %NO-mediated vasodilation (r = -0.42, P = 0.02). Serum[25(OH)D] was positively related to %NO (r = 0.41, P = 0.02). Controlling for [25(OH)D] weakened the association between M-index and %NO-mediated dilation (P = 0.16, r = -0.26). There was a negative curvilinear relation between [25(OH)D] and circulating IL-6 (r = -0.56, P < 0.001), but not TNF-α or IL-10 (P ≥ 0.14). IL-6 was not associated with %NO-mediated vasodilation (P = 0.44). These data suggest that vitamin D insufficiency/deficiency may contribute to reduced microvascular endothelial function in healthy, darkly pigmented young adults.NEW & NOTEWORTHY Endothelial dysfunction, an antecedent to hypertension and overt CVD, is commonly observed in otherwise healthy Black adults, although the underlying causes remain unclear. We show that reduced vitamin D availability with increasing degrees of skin pigmentation is associated with reduced microvascular endothelial function, independent of race or ethnicity, in healthy young adults. Greater prevalence of vitamin D deficiency in more darkly pigmented individuals may predispose them to increased risk of endothelial dysfunction.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Gabrielle A Dillon
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Lacy M Alexander
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Nina G Jablonski
- Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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15
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Vecellio DJ, Wolf ST, Cottle RM, Kenney WL. Utility of the Heat Index in defining the upper limits of thermal balance during light physical activity (PSU HEAT Project). Int J Biometeorol 2022; 66:1759-1769. [PMID: 35778555 PMCID: PMC9418276 DOI: 10.1007/s00484-022-02316-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 06/07/2022] [Accepted: 06/18/2022] [Indexed: 06/01/2023]
Abstract
Extreme heat events and consequent detrimental heat-health outcomes have been increasing in recent decades and are expected to continue with future climate warming. While many indices have been created to quantify the combined atmospheric contributions to heat, few have been validated to determine how index-defined heat conditions impact human health. However, this subset of indices is likely not valid for all situations and populations nor easily understood and interpreted by health officials and the public. In this study, we compare the ability of thresholds determined from the National Weather Service's (NWS) Heat Index (HI), the Wet Bulb Globe Temperature (WBGT), and the Universal Thermal Climate Index (UTCI) to predict the compensability of human heat stress (upper limits of heat balance) measured as part of the Pennsylvania State University's Heat Environmental Age Thresholds (PSU HEAT) project. While the WBGT performed the best of the three indices for both minimal activities of daily living (MinAct; 83 W·m-2) and light ambulation (LightAmb; 133 W·m-2) in a cohort of young, healthy subjects, HI was likewise accurate in predicting heat stress compensability in MinAct conditions. HI was significantly correlated with subjects' perception of temperature and humidity as well as their body core temperature, linking perception of the ambient environment with physiological responses in MinAct conditions. Given the familiarity the public has with HI, it may be better utilized in the expansion of safeguard policies and the issuance of heat warnings during extreme heat events, especially when access to engineered cooling strategies is unavailable.
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Affiliation(s)
- Daniel J Vecellio
- Center for Health Aging, College of Health and Human Development, Pennsylvania State University, 422 Biobehavioral Health Building, University Park, PA, 16802, USA.
| | - S Tony Wolf
- Department of Kinesiology, Pennsylvania State University, University Park, PA, 16802, USA
| | - Rachel M Cottle
- Department of Kinesiology, Pennsylvania State University, University Park, PA, 16802, USA
| | - W Larry Kenney
- Center for Health Aging, College of Health and Human Development, Pennsylvania State University, 422 Biobehavioral Health Building, University Park, PA, 16802, USA
- Department of Kinesiology, Pennsylvania State University, University Park, PA, 16802, USA
- Graduate Program in Physiology, Pennsylvania State University, University Park, PA, 16802, USA
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16
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Abstract
Little is known about the separate and combined influences of humidity conditions, sex, and aerobic fitness on heat tolerance in unacclimatized males and females. The purpose of the current study was to describe heat tolerance, in terms of critical WBGT (WBGTcrit), in unacclimatized young males and females in hot-dry (HD) and warm-humid (WH) environments. Eighteen subjects (9 M/9F; 21 ± 2 yr) were tested during exercise at 30% V̇O2max in a controlled environmental chamber. Progressive heat stress exposures were performed with either (1) constant dry-bulb temperature (Tdb) of 34 and 36 °C and increasing ambient water vapor pressure (Pa) (Pcrit trials; WH); or (2) constant Pa of 12 and 16 mmHg and increasing Tdb (Tcrit trials; HD). Chamber Tdb and Pa, and subject esophageal temperature (Tes), were continuously monitored throughout each trial. After a 30-min equilibration period, progressive heat stress continued until subject heat balance could no longer be maintained and a clear rise in Tes was observed. Absolute WBGTcrit and WBGTcrit adjusted to a metabolic rate of 300 W (WBGT300), and the difference between WBGTcrit and occupational exposure limits (OEL; ΔOEL) was assessed. WBGTcrit, WBGT300, and ΔOEL were higher in WH compared to HD (p < 0.0001) for females but were the same between environments for males (p ≥ 0.21). WBGTcrit was higher in females compared to males in WH (p < 0.0001) but was similar between sexes in HD (p = 0.44). When controlling for metabolic rate, WBGT300 and ΔOEL were higher in males compared to females in WH and HD (both p < 0.0001). When controlling for sex, V̇O2max was not associated with WBGT300 or ΔOEL for either sex (r ≤ 0.12, p ≥ 0.49). These findings suggest that WBGTcrit is higher in females compared to males in WH, but not HD, conditions. Additionally, the WBGTcrit is lower in females, but not males, in HD compared to WH conditions.
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Affiliation(s)
- S. Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Thomas E. Bernard
- College of Public Health, University of South Florida, Tampa, Florida
| | - W. Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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17
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Abstract
Critical environmental limits are those combinations of ambient temperature and humidity above which heat balance cannot be maintained for a given metabolic heat production, limiting exposure time, and placing individuals at increased risk of heat-related illness. The aim of this study was to establish those limits in young (18-34 yr) healthy adults during low-intensity activity approximating the metabolic demand of activities of daily living. Twenty-five (12 men/13 women) subjects were exposed to progressive heat stress in an environmental chamber at two rates of metabolic heat production chosen to represent minimal activity (MinAct) or light ambulation (LightAmb). Progressive heat stress was performed with either 1) constant dry-bulb temperature (Tdb) and increasing ambient water vapor pressure (Pa) (Pcrit trials; 36°C, 38°C, or 40°C) or 2) constant Pa and increasing Tdb (Tcrit trials; 12, 16, or 20 mmHg). Each subject was tested during MinAct and LightAmb in two to three experimental conditions in random order, for a total of four to six trials per participant. Higher metabolic heat production (P < 0.001) during LightAmb compared with MinAct trials resulted in significantly lower critical environmental limits across all Pcrit and Tcrit conditions (all P < 0.001). These data, presented graphically herein on a psychrometric chart, are the first to define critical environmental limits for young adults during activity resembling those of light household tasks or other activities of daily living and can be used to develop guidelines, policy decisions, and evidence-based alert communications to minimize the deleterious impacts of extreme heat events.NEW & NOTEWORTHY Critical environmental limits are those combinations of temperature and humidity above which heat balance cannot be maintained, placing individuals at increased risk of heat-related illness. Those limits have been investigated in young adults during exercise at 30% V̇o2max, but not during metabolic rates that approximate those of light activities of daily living. Herein, we establish critical environmental limits for young adults at two metabolic rates that reflect activities of daily living and leisurely walking.
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Affiliation(s)
- S. Tony Wolf
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Rachel M. Cottle
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Daniel J. Vecellio
- 2Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania
| | - W. Larry Kenney
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania,2Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania,3The Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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18
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Cottle RM, Wolf ST, Lichter ZS, Kenney WL. Validity and reliability of a protocol to establish human critical environmental limits (PSU HEAT Project). J Appl Physiol (1985) 2022; 132:334-339. [PMID: 34913735 PMCID: PMC8799392 DOI: 10.1152/japplphysiol.00736.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The PSU HEAT protocol has been used to determine critical environmental limits, i.e., those combinations of ambient temperature and humidity above which heat stress becomes uncompensable and core temperature rises continuously. However, no studies have rigorously investigated the reliability and validity of this experimental protocol. Here, we assessed the 1) between-visit reliability and 2) validity of the paradigm. Twelve subjects (5 M/7W; 25 ± 4 yr) completed a progressive heat stress protocol during which they walked on a treadmill (2.2 mph, 3% gradient) in a controllable environmental chamber. After an equilibration period, either dry-bulb temperature (Tdb) was increased every 5 min while ambient water vapor pressure (Pa) was held constant (Tcrit experiments) or Pa was increased every 5 min while Tdb was held constant (Pcrit experiments) until an upward inflection in gastrointestinal temperature (Tgi) was observed. For reliability experiments, 11 subjects repeated the same protocol on a different day. For validity experiments, 10 subjects performed a Tcrit experiment at their previously determined Pcrit or vice versa. The between-visit reliability (intraclass correlation coefficient, ICC) for critical environmental limits was 0.98. Similarly, there was excellent agreement between original and validity trials for Tcrit (ICC = 0.95) and Pcrit (ICC = 0.96). Furthermore, the wet-bulb temperature at the Tgi inflection point was not different during reliability (P = 0.78) or validity (P = 0.32) trials compared with original trials. These findings support the reliability and validity of this experimental paradigm for the determination of critical environmental limits for maintenance of human heat balance.NEW & NOTEWORTHY The PSU HEAT progressive heat stress protocol has been used to identify critical environmental limits for various populations, clothing ensembles, and metabolic intensities. However, no studies have rigorously investigated the reliability and validity of this experimental model. Here, we demonstrate excellent reliability and validity of the PSU HEAT protocol.
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Affiliation(s)
- Rachel M. Cottle
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - S. Tony Wolf
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Zachary S. Lichter
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - W. Larry Kenney
- 1Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania,2Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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19
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Vecellio DJ, Wolf ST, Cottle RM, Kenney WL. Evaluating the 35°C wet-bulb temperature adaptability threshold for young, healthy subjects (PSU HEAT Project). J Appl Physiol (1985) 2022; 132:340-345. [PMID: 34913738 PMCID: PMC8799385 DOI: 10.1152/japplphysiol.00738.2021] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
A wet-bulb temperature of 35°C has been theorized to be the limit to human adaptability to extreme heat, a growing concern in the face of continued and predicted accelerated climate change. Although this theorized threshold is based in physiological principles, it has not been tested using empirical data. This study examined the critical wet-bulb temperature (Twb,crit) at which heat stress becomes uncompensable in young, healthy adults performing tasks at modest metabolic rates mimicking basic activities of daily life. Across six experimentally determined environmental limits, no subject's Twb,crit reached the 35°C limit and all means were significantly lower than the theoretical 35°C threshold. Mean Twb,crit values were relatively constant across 36°C -40°C humid environments and averaged 30.55 ± 0.98°C but progressively decreased (higher deviation from 35°C) in hotter, dry ambient environments. Twb,crit was significantly associated with mean skin temperature (and a faster warming rate of the skin) due to larger increases in dry heat gain in the hot-dry environments. As sweat rates did not significantly differ among experimental environments, evaporative cooling was outpaced by dry heat gain in hot-dry conditions, causing larger deviations from the theoretical 35°C adaptability threshold. In summary, a wet-bulb temperature threshold cannot be applied to human adaptability across all climatic conditions and where appropriate (high humidity), that threshold is well below 35°C.NEW & NOTEWORTHY This study is the first to use empirical physiological observations to examine the well-publicized theoretical 35°C wet-bulb temperature limit for human to extreme environments. We find that uncompensable heat stress in humid environments occurs in young, healthy adults at wet-bulb temperatures significantly lower than 35°C. In addition, uncompensable heat stress occurs at widely different wet-bulb temperatures as a function of ambient vapor pressure.
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Affiliation(s)
- Daniel J. Vecellio
- 1Center for Healthy Aging, Pennsylvania State University, University Park, Pennsylvania
| | - S. Tony Wolf
- 2Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania
| | - Rachel M. Cottle
- 2Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania
| | - W. Larry Kenney
- 1Center for Healthy Aging, Pennsylvania State University, University Park, Pennsylvania,2Department of Kinesiology, Pennsylvania State University, University Park, Pennsylvania,3Graduate Program in Physiology, Pennsylvania State University, University Park, Pennsylvania
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20
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Dillon GA, Wolf ST, Alexander LM. Nitric oxide-mediated cutaneous microvascular function is not altered in young adults following mild-to-moderate SARS CoV-2 infection. Am J Physiol Heart Circ Physiol 2022; 322:H319-H327. [PMID: 34995164 PMCID: PMC8803551 DOI: 10.1152/ajpheart.00602.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/05/2022] [Accepted: 01/05/2022] [Indexed: 11/22/2022]
Abstract
Vascular dysfunction has been reported in adults who have recovered from COVID-19. To date, no studies have investigated the underlying mechanisms of persistent COVID-19-associated vascular dysfunction. Our purpose was to quantify nitric oxide (NO)-mediated vasodilation in healthy adults who have recovered from SARS-CoV-2 infection. We hypothesized that COVID-19-recovered adults would have impaired NO-mediated vasodilation compared with adults who have not had COVID-19. In methods, we performed a cross-sectional study including 10 (5 men/5 women, 24 ± 4 yr) healthy control (HC) adults who were unvaccinated for COVID-19, 11 (4 men/7 women, 25 ± 6 yr) healthy vaccinated (HV) adults, and 12 (5 men/7 women, 22 ± 3 yr) post-COVID-19 (PC, 19 ± 14 wk) adults. COVID-19 symptoms severity (survey) was assessed. A standardized 39°C local heating protocol was used to assess NO-dependent vasodilation via perfusion (intradermal microdialysis) of 15 mM NG-nitro-l-arginine methyl ester during the plateau of the heating response. Red blood cell flux was measured (laser-Doppler flowmetry) and cutaneous vascular conductance (CVC = flux/mmHg) was expressed as a percentage of maximum (28 mM sodium nitroprusside + 43°C). In results, the local heating plateau (HC: 61 ± 20%, HV: 60 ± 19%, PC: 67 ± 19%, P = 0.80) and NO-dependent vasodilation (HC: 77 ± 9%, HV: 71 ± 7%, PC: 70 ± 10%, P = 0.36) were not different among groups. Neither symptom severity (25 ± 12 AU) nor time since diagnosis correlated with the NO-dependent vasodilation (r = 0.46, P = 0.13; r = 0.41, P = 0.19, respectively). In conclusion, healthy adults who have had mild-to-moderate COVID-19 do not have altered NO-mediated cutaneous microvascular function.NEW & NOTEWORTHY Healthy young adults who have had mild-to-moderate COVID-19 do not display alterations in nitric oxide-mediated cutaneous microvascular function. In addition, healthy young adults who have COVID-19 antibodies from the COVID-19 vaccinations do not display alterations in nitric oxide-mediated cutaneous microvascular function.
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Affiliation(s)
- Gabrielle A Dillon
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania
| | - S Tony Wolf
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Lacy M Alexander
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
- Center for Healthy Aging, The Pennsylvania State University, University Park, Pennsylvania
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21
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Berry CW, Wolf ST, Cottle RM, Kenney WL. Hydration Is More Important Than Exogenous Carbohydrate Intake During Push-to-the-Finish Cycle Exercise in the Heat. Front Sports Act Living 2021; 3:742710. [PMID: 34746777 PMCID: PMC8568039 DOI: 10.3389/fspor.2021.742710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/23/2021] [Indexed: 11/13/2022] Open
Abstract
Dehydration ≥2% loss of body mass is associated with reductions in performance capacity, and carbohydrate (CHO)-electrolyte solutions (CES) are often recommended to prevent dehydration and provide a source of exogenous carbohydrate during exercise. It is also well established that performance capacity in the heat is diminished compared to cooler conditions, a response attributable to greater cardiovascular strain caused by high skin and core temperatures. Because hydration status, environmental conditions, and carbohydrate availability interact to influence performance capacity, we sought to determine how these factors affect push-to-the-finish cycling performance. Ten young trained cyclists exercised at a moderate intensity (2.5 W·kg-1) in a hot-dry condition [40°C, 20% relative humidity (RH)] until dehydration of ~2% body mass. Subjects then consumed either no fluid (NF) or enough fluid (water, WAT; Gatorade®, GAT; or GoodSport™, GS) to replace 75% of lost body mass over 30 min. After a 30-min light-intensity warm-up (1.5 W·kg-1) in a 35°C, 20% RH environment, subjects then completed a 120-kJ time trial (TT). TT time-to-completion, absolute power, and relative power were significantly improved in WAT (535 ± 214 s, 259 ± 99 W, 3.3 ± 0.9 W·kg-1), GAT (539 ± 226 s, 260 ± 110 W, 3.3 ± 1.0 W·kg-1), and GS (534 ± 238 s, 262 ± 105 W, 3.4 ± 1.0 W·kg-1) compared to NF (631 ± 310 s, 229 ± 96 W, 3.0 ± 0.9 W·kg-1) all (p < 0.01) with no differences between WAT, GAT, and GS, suggesting that hydration is more important than carbohydrate availability during exercise in the heat. A subset of four subjects returned to the laboratory to repeat the WAT, GAT, and GS treatments to determine if between-beverage differences in time-trial performance were evident with a longer TT in thermoneutral conditions. Following dehydration, the ambient conditions in the environmental chamber were reduced to 21°C and 20% RH and subjects completed a 250-kJ TT. All four subjects improved TT performance in the GS trial (919 ± 353 s, 300 ± 100 W, 3.61 ± 0.86 W·kg-1) compared to WAT (960 ± 376 s, 283 ± 91 W, 3.43 ± 0.83 W·kg-1), while three subjects improved TT performance in the GAT trial (946 ± 365 s, 293 ± 103 W, 3.60 ± 0.97 W·kg-1) compared to WAT, highlighting the importance of carbohydrate availability in cooler conditions as the length of a push-to-the-finish cycling task increases.
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Affiliation(s)
- Craig W Berry
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, United States
| | - S Tony Wolf
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, United States
| | - Rachel M Cottle
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, United States
| | - W Larry Kenney
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, United States.,Graduate Program in Physiology, The Pennsylvania State University, University Park, PA, United States
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22
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Abstract
PURPOSE OF REVIEW Vitamin D and folate promote vascular endothelial health and may therefore help mitigate the development of cardiovascular disease (CVD). Ultraviolet radiation (UVR) exposure stimulates cutaneous vitamin D synthesis but degrades the bioactive metabolite of folate, 5-methyltetrahydrofolate (5-MTHF). Skin melanin absorbs UVR, thereby modulating the impact of UVR exposure on vitamin D and 5-MTHF metabolism. This review presents recent findings regarding the inter-relations among UVR, skin pigmentation, folate and vitamin D, and endothelial function. RECENT FINDINGS Evidence for roles of folic acid or vitamin D supplementation on CVD endpoints is inconsistent, although preclinical and clinical studies have demonstrated the efficacy of both micronutrients for improving endothelial function. Vitamin D deficiency is most prevalent in darkly pigmented individuals living in relatively low-UVR environments. Conversely, there is a negative relation between accumulated UVR exposure and serum folate concentration in lightly pigmented adults. The interactions among UVR and bioavailable folate and vitamin D differentially impact endothelial function in differently pigmented skin. SUMMARY UVR exposure disparately impacts folate and vitamin D metabolism in differently pigmented skin depending upon regional UVR intensity and seasonality. These findings present new clinical research questions regarding the interactions among UVR, skin pigmentation, folate and vitamin D bioavailability, and endothelial health.
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Affiliation(s)
| | - W. Larry Kenney
- Department of Kinesiology
- Graduate Program in Physiology, The Pennsylvania State University, University Park, PA, USA
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23
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Wolf ST, Folkerts MA, Cottle RM, Daanen HAM, Kenney WL. Metabolism- and sex-dependent critical WBGT limits at rest and during exercise in the heat. Am J Physiol Regul Integr Comp Physiol 2021; 321:R295-R302. [PMID: 34259026 DOI: 10.1152/ajpregu.00101.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Critical environmental limits are environmental thresholds above which heat gain exceeds heat loss and body core temperature (Tc) cannot be maintained at equilibrium. Those limits can be represented as critical wet-bulb globe temperature (WBGTcrit), a validated index that represents the overall thermal environment. Little is known about WBGTcrit at rest and during low-to-moderate intensity exercise, or sex differences in WBGTcrit, in unacclimated young adults. The following hypotheses were tested: 1) WBGTcrit progressively decreases as metabolic heat production (Mnet) increases, 2) no sex differences in WBGTcrit occur at rest, and 3) WBGTcrit is lower during absolute-intensity exercise but higher at relative intensities in women than in men. Thirty-six participants [19 men (M)/17 women (W); 23 ± 4 yr] were tested at rest, during light, absolute-intensity exercise (10 W), or during moderate, relative-intensity exercise [30% maximal oxygen consumption (V̇o2max)] in an environmental chamber. Dry-bulb temperature was clamped as relative humidity or ambient water vapor pressure was increased until an upward inflection was observed in Tc (rectal or esophageal temperature). Sex-aggregated WBGTcrit was lower during 10 W (32.9°C ± 1.7°C, P < 0.0001) and 30% V̇o2max (31.6°C ± 1.1°C, P < 0.0001) exercise versus at rest (35.3°C ± 0.8°C), and lower at 30% V̇o2max versus 10 W (P = 0.01). WBGTcrit was similar between sexes at rest (35.6°C ± 0.8°C vs. 35.0°C ± 0.8°C, P = 0.83), but lower during 10 W (31.9°C ± 1.7°C vs. 34.1°C ± 0.3°C, P < 0.01) and higher during 30% V̇o2max (32.4°C ± 0.8°C vs. 30.8°C ± 0.9°C, P = 0.03) exercise in women versus men. These findings suggest that WBGTcrit decreases as Mnet increases, no sex differences occur in WBGTcrit at rest, and sex differences in WBGTcrit during exercise depend on absolute versus relative intensities.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Mireille A Folkerts
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Rachel M Cottle
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Hein A M Daanen
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
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24
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Wolf ST, Jablonski N, Ferguson S, Alexander L, Kenney WL. Skin Pigmentation is Negatively Associated with Both Circulating Vitamin D Concentration and Cutaneous Microvascular Endothelial Function. FASEB J 2021. [DOI: 10.1096/fasebj.2021.35.s1.03552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- S. Tony Wolf
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
| | - Nina Jablonski
- AnthropologyThe Pennsylvania State UniversityUniversity ParkPA
| | - Sara Ferguson
- DermatologyThe Pennsylvania State UniversityState CollegePA
| | - Lacy Alexander
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
| | - W. Larry Kenney
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
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25
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Abstract
Reflex cutaneous vasodilation during heating is attenuated in healthy human aging secondary to blunted increases in efferent skin sympathetic nervous system activity (SSNA) and reductions in end-organ sensitivity. Whether age-related alterations in the mean body temperature ( T - b) threshold for increasing SSNA and/or the sensitivity of responses are evident with aging have not been examined. We tested the hypotheses that the Tb threshold for SSNA and cutaneous vascular conductance (CVC) would be increased, but the sensitivity would be reduced, with aging. Reflex vasodilation was induced in 13 young (23 ± 3 y) and 13 older (67 ± 7 y) adults using a water-perfused suit to systematically increase mean skin and esophageal temperatures. SSNA (peroneal microneurography) and red cell flux (laser Doppler flowmetry) in the innervated dermatome were continuously measured. SSNA was normalized to baseline; CVC was normalized as a percentage of maximal CVC. Baseline T - b was lower in older adults (36.0 ± 0.4°C vs 36.4 ± 0.3°C; p = 0.005). During passive heating, the ∆ T - b thresholds for increasing SSNA and CVC were greater (1.3 ± 0.4°C vs 0.9 ± 0.3°C; p = 0.007 and 1.3 ± 0.4°C vs 0.8 ± 0.3°C; p = 0.002, respectively) in older adults. The slope of the relation between both SSNA (0.31 ± 0.23 vs 0.13 ± 0.10 V⋅s⋅°C -1; p = 0.01) and CVC (87.5 ± 50.1 vs 32.4 ± 18.1%max⋅°C-1; p = 0.002) vs T - b was lower in older adults. The relative T - b threshold for activation of SSNA and the initiation of reflex cutaneous vasodilation is higher in older adults, and once activated, the sensitivity of both responses is diminished, supporting the concept that the efferent component of the thermoregulatory reflex arc is impaired in healthy aging. Abbreviations: CI: confidence interval; CVC: cutaneous vascular conductance; SSNA: skin sympathetic nervous system activity; T - b: mean body temperature; Tes: esophageal temperature; T - sk: mean skin temperature.
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Affiliation(s)
- Jody L Greaney
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA.,Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - Anna E Stanhewicz
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA.,Department of Health and Human Physiology, The University of Iowa, Iowa City, IA, USA
| | - S Tony Wolf
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA
| | - W Larry Kenney
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA
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26
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Abstract
Racial disparities in cardiovascular and cerebrovascular health outcomes are well described, and recent research has shed light on the mechanistic underpinnings of those disparities. However, "race" is a social construct that is poorly defined and continually evolving and is historically based on faulty premises. The continued categorization by race in physiological research suggests that there are inherent differences between races, rather than addressing the specific underlying factors that result in health disparities between groups. The purpose of this Perspectives article is to provide a brief history of the genesis of categorization by race, why such categorization should be reconsidered in physiology research, and offer recommendations to more directly investigate the underlying factors that result in group disparities in cardiovascular and cerebrovascular health.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Nina G Jablonski
- Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania.,Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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27
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Wolf ST, Jablonski NG, Ferguson SB, Alexander LM, Kenney WL. Four weeks of vitamin D supplementation improves nitric oxide-mediated microvascular function in college-aged African Americans. Am J Physiol Heart Circ Physiol 2020; 319:H906-H914. [PMID: 32857616 DOI: 10.1152/ajpheart.00631.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Reduced nitric oxide (NO)-mediated cutaneous vasodilation, secondary to increased oxidative stress, presents in young African American (AA) compared with European American (EA) adults and may be modulated by vitamin D status. We assessed cutaneous microvascular function in 18 young, healthy (21 ± 2 yr; 9 men, 9 women) subjects before (pre, 8 AA, 10 EA) 4 wk of 2,000 IU/day oral vitamin D supplementation and in 13 subjects after (post, 7 AA, 6 EA) 4 wk of 2,000 IU/day oral vitamin D supplementation. Serum vitamin D concentrations [25(OH)D] were measured at each visit. Three intradermal microdialysis fibers placed in the ventral forearm were randomized for treatment with 10 μM Tempol, 100 μM apocynin, or lactated Ringer's solution (control). Local heating (39°C) induced cutaneous vasodilation; red cell flux was measured at each site (laser-Doppler flowmetry), and cutaneous vascular conductance (CVC = flux/MAP) was expressed as a percentage of maximum (28 mM sodium nitroprusside, +43°C) for each phase of local heating. After stable elevated blood flow was attained, 15 mM NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) was perfused at all sites to quantify the NO contribution to cutaneous vasodilation (%NO), calculated as the difference between local heating and l-NAME plateaus. Serum [25(OH)D], the magnitude of the local heating response, and %NO were all lower in AAs versus EAs (P < 0.01). Tempol (P = 0.01), but not apocynin (P ≥ 0.19), improved the local heating response and %NO. Four weeks of supplementation improved serum [25(OH)D], the local heating response, and %NO in AAs (P ≤ 0.04) but not in EAs (P ≥ 0.41). Vitamin D supplementation mitigated endothelial dysfunction, an antecedent to overt cardiovascular disease (CVD), in otherwise healthy, young AA adults.NEW & NOTEWORTHY Endothelial dysfunction, an antecedent to overt cardiovascular disease (CVD), is observed earlier and more frequently in otherwise healthy African Americans (AAs) when compared with other ethnic groups. Vitamin D may modulate endothelial function, and darkened skin pigmentation increases risk of vitamin D deficiency. We show that 4 wk of 2,000 IU/day vitamin D supplementation improves microvascular responses to local heating in AAs. Ensuring adequate vitamin D status may mitigate development of cardiovascular dysfunction in this at-risk population.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - Nina G Jablonski
- Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania
| | - Sara B Ferguson
- Department of Dermatology, The Penn State Hershey Medical Group, State College, Pennsylvania
| | - Lacy M Alexander
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania.,Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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28
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Abstract
Overexposure to ultraviolet radiation (UVR) from the sun is associated with deleterious health effects including, but not limited to, increased risk of skin cancers. Military personnel and those who participate in outdoor exercise or sports represent two potential populations at elevated risk of negative health consequences of UVR exposure due to large amounts of time spent outdoors, often in harsh UVR environments. Despite exposure to high and/or frequent doses of UVR in recreational and tactical athletes, adequate sun-protection practices are often disregarded or not well understood by many within these at-risk populations, resulting in heightened risk of negative UVR effects. The focus of this review is to examine the available literature regarding UVR exposure, risk of adverse health effects of UVR exposure, and sun protection practices in outdoor exercisers, athletes, and military personnel.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, PA
| | - Lauren E Kenney
- Uniformed Services University of the Health Sciences, Bethesda, MD
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29
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Wolf ST, Greaney JL, Stanhewicz AE, Alexander LM, Kenney WL. The Nitric Oxide Contribution to Reflex Cutaneous Vasodilation During Intradermal Microdialysis is Similar When Quantified Either Within or Between Sites. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.02572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Jody L. Greaney
- The Pennsylvania State University
- The University of Texas at Arlington
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30
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Wolf ST, Berry CW, Dillon GA. A role for endothelin-A receptors in altered blood flow and pressor responses during exercise in hypertensive adults. J Physiol 2019; 598:441-442. [PMID: 31856308 DOI: 10.1113/jp279344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, 16802
| | - Craig W Berry
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, 16802
| | - Gabrielle A Dillon
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, 16802
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31
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Abstract
The vitamin D-folate hypothesis has been proposed as an explanation for the evolution of human skin pigmentation. According to this hypothesis, a darkened skin pigment was adapted by early human populations living in equatorial Africa to protect against photodegradation of bioavailable folate by ultraviolet radiation (UVR). As humans moved away from the equator to more northern latitudes and occupied regions of lower UVR exposure and greater seasonal variation, however, depigmentation occurred to allow for adequate biosynthesis of vitamin D. Vitamin D and folate are both recognized for their evolutionary importance in healthy pregnancy and early childhood development. More recently, evidence has emerged demonstrating the importance of both vitamin D and folate in vascular health via their effects in reducing oxidative stress and improving nitric oxide (NO) bioavailability. Thus, populations with darkened skin pigmentation may be at elevated risk of vascular dysfunction and cardiovascular disease in low UVR environments due to hypovitaminosis D; particularly important as darkly-pigmented African-Americans represent an at-risk population for cardiovascular disease. Conversely, lightly pigmented populations in high UVR environments may be at risk of deleterious vascular effects of UVR-induced folate degradation. The focus of this review is to explore the currently available literature regarding the potential role of UVR in vascular health via its differential effects on vitamin D and folate metabolism, as well as the interaction between skin pigmentation, genetics, and environment in modulating the vascular influence of UVR exposure.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania.,Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania
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32
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Clarke MM, Stanhewicz AE, Wolf ST, Cheuvront SN, Kenefick RW, Kenney WL. A randomized trial to assess beverage hydration index in healthy older adults. Am J Clin Nutr 2019; 109:1640-1647. [PMID: 31051498 PMCID: PMC6537935 DOI: 10.1093/ajcn/nqz009] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 01/16/2019] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND The beverage hydration index (BHI) is a composite measure of fluid balance after consuming a test beverage relative to water. BHI is a relatively new measure that has been explored in young, but not yet older, adults. OBJECTIVE The aim of this study was to investigate potential differences in BHI between euhydrated younger and older adults after drinking 4 different commercial beverages. We hypothesized that 1) older subjects would remain in positive fluid balance longer than young subjects after ingestion of each test beverage due to decreased urinary excretion rates, 2) glucose (glu)- and amino acid (AA)-based hydration beverages with sodium would have a BHI greater than water in both groups, and 3) the traditional 2-h postingestion BHI may be inappropriate for older adults. METHODS On 5 separate visits, 12 young (23 ± 3 yr, 7 M/5F) and 12 older (67 ± 6 yr, 5 M/7F) subjects consumed 1 L of distilled water, G-20 (6% CHO, 20 mmol/L Na+), G-45 (2.5% CHO, 45 mmol/L Na+), AA-30 (5 AAs, 30 mmol/L Na+), or AA-60 (8 AAs, 60 mmol/L Na+) over 30 min. Blood and urine samples were collected before ingestion and at 0, 60, 120, 180, and 240 min postingestion with additional venous blood sampling at 5, 10, 15, and 30 min postingestion. RESULTS In young subjects, BHI increased with increasing beverage Na+ concentration, and AA-60 had the highest BHI (AA-60 = 1.24 ± 0.10 compared with water = 1.00, P = 0.01). For older subjects, BHI was highest in AA-30 (AA-30; 1.20 ± 0.13 compared with water, P < 0.01) and was still in flux beyond 2 h in AA-60 (P < 0.05). CONCLUSIONS Beverage Na+ content progressively increased BHI in young adults independent of glucose or AA content. For older adults, the AA-30 beverage had the highest BHI. A 4-h BHI may be more appropriate for older adults due to attenuated urine excretion rates. This trial was registered at clinicaltrials.gov as NCT03559101.
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Affiliation(s)
- Megan M Clarke
- Department of Kinesiology, The Pennsylvania State University, University Park, PA
| | - Anna E Stanhewicz
- Department of Kinesiology, The Pennsylvania State University, University Park, PA
| | - S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, PA
| | - Samuel N Cheuvront
- US Army Research Institute of Environmental Medicine (USARIEM), Natick, MA
| | - Robert W Kenefick
- US Army Research Institute of Environmental Medicine (USARIEM), Natick, MA
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, PA,Address correspondence to WLK (e-mail: )
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33
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Wolf ST, Berry CW, Stanhewicz AE, Kenney LE, Ferguson SB, Kenney WL. Sunscreen or simulated sweat minimizes the impact of acute ultraviolet radiation on cutaneous microvascular function in healthy humans. Exp Physiol 2019; 104:1136-1146. [PMID: 31004462 DOI: 10.1113/ep087688] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 04/18/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Are ultraviolet radiation (UVR)-induced increases in skin blood flow independent of skin erythema? Does broad-spectrum UVR exposure attenuate NO-mediated cutaneous vasodilatation, and does sunscreen or sweat modulate this response? What are the main findings and their importance? Erythema and vascular responses to UVR are temporally distinct, and sunscreen prevents both responses. Exposure to UVR attenuates NO-mediated vasodilatation in the cutaneous microvasculature; sunscreen or simulated sweat on the skin attenuates this response. Sun over-exposure may elicit deleterious effects on human skin that are separate from sunburn, and sunscreen or sweat on the skin may provide protection. ABSTRACT Exposure to ultraviolet radiation (UVR) may result in cutaneous vascular dysfunction independent of erythema (skin reddening). Two studies were designed to differentiate changes in erythema from skin vasodilatation throughout the 8 h after acute broad-spectrum UVR exposure with (+SS) or without SPF-50 sunscreen (study 1) and to examine NO-mediated cutaneous vasodilatation after acute broad-spectrum UVR exposure with or without +SS or simulated sweat (+SW) on the skin (study 2). In both studies, laser-Doppler flowmetry was used to measure red cell flux, and cutaneous vascular conductance (CVC) was calculated (CVC = flux/mean arterial pressure). In study 1, in 14 healthy adults (24 ± 4 years old; seven men and seven women), the skin erythema index and CVC were measured over two forearm sites (UVR only and UVR+SS) before, immediately after and every 2 h for 8 h post-exposure (750 mJ cm-2 ). The erythema index began to increase immediately post-UVR (P < 0.05 at 4, 6 and 8 h), but CVC did not increase above baseline for the first 4-6 h (P ≤ 0.01 at 6 and 8 h); +SS prevented both responses. In study 2, in 13 healthy adults (24 ± 4 years old; six men and seven women), three intradermal microdialysis fibres were placed in the ventral skin of the forearm [randomly assigned to UVR (450 mJ cm-2 ), UVR+SS or UVR+SW], and one fibre (non-exposed control; CON) was placed in the contralateral forearm. After UVR, a standardized local heating (42°C) protocol quantified the percentage of NO-mediated vasodilatation (%NO). The UVR attenuated %NO compared with CON (P = 0.01). The diminished %NO was prevented by +SS (P < 0.01) and +SW (P < 0.01). Acute broad-spectrum UVR attenuates NO-dependent dilatation in the cutaneous microvasculature, independent of erythema. Sunscreen protects against both inflammatory and heating-induced endothelial dysfunction, and sweat might prevent UVR-induced reductions in NO-dependent dilatation.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA
| | - Craig W Berry
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA
| | - Anna E Stanhewicz
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA
| | - Lauren E Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA.,Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Sara B Ferguson
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA.,Department of Dermatology, The Penn State Hershey Medical Group, State College, PA, USA
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, University Park, PA, USA.,Graduate Program in Physiology, The Pennsylvania State University, University Park, PA, USA
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Berry CW, Hill IN, Wolf ST, Stanhewicz AE, Kenney WL. Skin Erythema and Blood Flow Responses to Acute Ultraviolet Radiation Exposure. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.541.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Craig W. Berry
- KinesiologyPennsylvania State UniversityUniversity ParkPA
| | | | - S. Tony Wolf
- KinesiologyPennsylvania State UniversityUniversity ParkPA
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35
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Wolf ST, Stanhewicz AE, Clarke MM, Cheuvront SN, Kenefick RW, Kenney WL. Age-related differences in water and sodium handling after commercial hydration beverage ingestion. J Appl Physiol (1985) 2019; 126:1042-1048. [PMID: 30763158 PMCID: PMC6485687 DOI: 10.1152/japplphysiol.01094.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/08/2019] [Accepted: 02/08/2019] [Indexed: 12/28/2022] Open
Abstract
Aging is associated with altered water, electrolyte, and glucose handling. Alternative beverages to those containing carbohydrate (CHO) should be considered for older adults. We hypothesized that reduced sodium (CNa+) and/or water (CH2O) clearance would underlie greater beverage retention in older compared with young adults, secondary to reduced glomerular filtration rate (GFR). We further hypothesized that amino acid (AA)- and CHO-based beverages would promote retention better than water. Over five visits, 12 young (23 ± 3 yr; 7 men, 5 women) and 12 older (67 ± 6 yr; 5 men, 7 women) subjects consumed 1 liter of distilled water or beverages with 6% CHO, 0.46 g/l Na+ [Gatorade (GAT)]; 2.5% CHO, 0.74 g/l Na+ [Pedialyte (PED)]; 5 AA, 1.04 g/l Na+ [enterade (ENT)-5]; or 8 AA, 1.38 g/l Na+ (ENT-8) over 30 min. Blood and urine were collected every hour for 4 h after ingestion; retention, CH2O, and CNa+ were calculated at 2 and 4 h. Additional calculations adjusted CH2O and CNa+ for estimated GFR (eGFR). Water yielded the lowest retention in both groups ( P ≤ 0.02). Retention was higher in older vs. young adults except for ENT-8 at 4 h ( P = 0.73). CH2O was higher for older vs. young adults for GAT at 2 h ( P < 0.01) and GAT and PED at 4 h ( P < 0.01) after ingestion but was otherwise similar between groups. CNa+ was lower in older vs. young adults except for ENT-8 ( P ≥ 0.19). Adjusting for eGFR resulted in higher CH2O for all beverages in older vs. young adults ( P < 0.05) but did not influence CNa+. Older adults may better retain beverages with less Na+ than young adults because of reduced CNa+. AA- and CHO-based electrolyte-rich beverages may similarly promote beverage retention. NEW & NOTEWORTHY Commercially available amino acid (AA)-containing beverages may provide an alternative to traditional carbohydrate (CHO)-containing beverages, particularly for older adults with attenuated water, electrolyte, and glucose handling. We compared beverage retention and free water and sodium clearance between young and older adults after ingestion of water, two CHO-based beverages, and two AA-based beverages. Our data suggest that older adults better retain beverages with less sodium compared with young adults and that AA-based and CHO-based electrolyte-containing beverages similarly promote retention.
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Affiliation(s)
- S Tony Wolf
- Department of Kinesiology, The Pennsylvania State University , University Park, Pennsylvania
| | - Anna E Stanhewicz
- Department of Kinesiology, The Pennsylvania State University , University Park, Pennsylvania
| | - Megan M Clarke
- Department of Kinesiology, The Pennsylvania State University , University Park, Pennsylvania
| | - Samuel N Cheuvront
- US Army Research Institute of Environmental Medicine , Natick, Massachusetts
| | - Robert W Kenefick
- US Army Research Institute of Environmental Medicine , Natick, Massachusetts
| | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University , University Park, Pennsylvania
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36
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Wolf ST, Stanhewicz AE, Jablonski NG, Ferguson SB, Kenney WL. The Modulating Effects of Sunscreen and Simulated Sweat on Ultraviolet Radiation‐ Induced Microvascular Dysfunction in the Human Cutaneous Vasculature. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.541.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- S. Tony Wolf
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
| | | | | | | | - W. Larry Kenney
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
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37
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Wolf ST, Stanhewicz AE, Clarke MM, Cheuvront SN, Kenefick RW, Kenney WL. Age‐Related Differences in Water and Sodium Handling Following Commercial Hydration Beverage Ingestion. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.851.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- S. Tony Wolf
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
| | | | - Megan M. Clarke
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
| | | | | | - W. Larry Kenney
- KinesiologyThe Pennsylvania State UniversityUniversity ParkPA
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38
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Wolf ST, Stanhewicz AE, Jablonski NG, Kenney WL. Acute ultraviolet radiation exposure attenuates nitric oxide-mediated vasodilation in the cutaneous microvasculature of healthy humans. J Appl Physiol (1985) 2018; 125:1232-1237. [PMID: 30138076 DOI: 10.1152/japplphysiol.00501.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
5-methyltetrahydrofolate (5-MTHF) is important for nitric oxide (NO)-mediated cutaneous microvascular vasodilation. Ultraviolet B (UVB) radiation may deplete 5-MTHF, either directly or via production of reactive oxygen species (ROS), decreasing NO-mediated vasodilation. We hypothesized that 1) acute UVB exposure would attenuate NO-dependent cutaneous vasodilation, 2) local perfusion of 5-MTHF or ascorbate (ASC; anti-oxidant) would augment NO-dependent vasodilation after UVB, and 3) darker skin pigmentation would be UVB-protective. Three intradermal microdialysis fibers placed in each forearm of 21 healthy young adults (23±1 yr; 8M/13F) locally delivered lactated Ringer's (control), 5mM 5-MTHF, or 10mM ASC. One arm was UVB-exposed (300mJ/cm2), the other served as non-exposed control (CON). Following UVB exposure, a standardized local heating (42˚C) protocol induced cutaneous vasodilation. After attaining a plateau blood flow, 15mM NG-nitro-L-arginine methyl ester (L-NAME; nitric oxide synthase inhibiter) was infused at all sites to quantify the NO contribution. Red cell flux was measured at each site by laser-Doppler flowmetry (LDF) and cutaneous vascular conductance (CVC=LDF/MAP) was expressed as a percentage of maximum (%CVCmax; 28mM sodium nitroprusside+43°C). UVB attenuated NO-mediated vasodilation compared to CON (23.1±3.6 vs 33.9±3.4 %; p=0.001). Delivery of 5-MTHF or ASC improved NO-mediated vasodilation versus lactated Ringer's in the UVB-exposed arm (MTHF: 30.1±4.8 vs 23.1±3.8 %; p=0.03; ASC: 30.9±4.3 vs 23.1±3.8 %; p=0.02). Neither treatment affected the response in the non-exposed arm (p≥0.09). Skin pigmentation (M-index) was not predictive of the UVB response (p≥0.34). These data suggest that acute UVB exposure attenuates NO-mediated vasodilation via direct and/or ROS-induced reductions in 5-MTHF, independent of skin pigmentation.
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Affiliation(s)
- S Tony Wolf
- Kinesiology, The Pennsylvania State University, United States
| | - Anna E Stanhewicz
- Department of Kinesiology, The Pennsylvania State University, United States
| | | | - W Larry Kenney
- Department of Kinesiology, The Pennsylvania State University, United States
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Wolf ST, Stanhewicz AE, Garner TB, Jablonski NG, Kenney WL. Acute Ultraviolet Radiation Exposure Attenuates Nitric Oxide-Mediated Vasodilation in the Cutaneous Microvasculature. Med Sci Sports Exerc 2018. [DOI: 10.1249/01.mss.0000535557.79329.40] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Soble AR, Wolf ST. Operable breast carcinoma associated with refractory anemia. JAMA 1976; 235:277. [PMID: 946046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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