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Hasegawa D, Hori A, Okamura Y, Baba R, Suijo K, Mizuno M, Sugawara J, Kitatsuji K, Ogata H, Toda K, Hotta N. Aging exaggerates blood pressure response to ischemic rhythmic handgrip exercise in humans. Physiol Rep 2021; 9:e15125. [PMID: 34817113 PMCID: PMC8611780 DOI: 10.14814/phy2.15125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 11/02/2021] [Accepted: 11/02/2021] [Indexed: 12/23/2022] Open
Abstract
Ischemic skeletal muscle conditions are known to augment exercise-induced increases in blood pressure (BP). Aging is also a factor that enhances the pressor response to exercise. However, the effects of aging on the BP response to ischemic exercise remain unclear. We, therefore, tested the hypothesis that aging enhances the BP response to rhythmic handgrip (RHG) exercise during postexercise muscle ischemia (PEMI). We divided the normotensive participants without cardiovascular diseases into three age groups: young (n = 26; age, 18-28 years), middle-aged (n = 23; age, 35-59 years), and older adults (n = 23; age, 60-80 years). The participants performed RHG exercise with minimal effort for 1 min after rest with and without PEMI, which was induced by inflating a cuff on the upper arm just before the isometric handgrip exercise ended; the intensity was 30% of maximal voluntary contraction force. Under PEMI, the increase in diastolic BP (DBP) from rest to RHG exercise in the older adult group (Δ13 ± 2 mmHg) was significantly higher than that in the young (Δ5 ± 2 mmHg) and middle-aged groups (Δ6 ± 1 mmHg), despite there being no significant difference between the groups in the DBP response from rest to RHG exercise without PEMI. Importantly, based on multiple regression analysis, age remained a significant independent determinant of both the SBP and DBP responses to RHG exercise during PEMI (p < 0.01). These findings indicate that aging enhances the pressor response to ischemic rhythmic exercise.
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Affiliation(s)
- Daisuke Hasegawa
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- Nagoya Heisei College of Nursing and Medical CareNagoyaJapan
| | - Amane Hori
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- Japan Society for the Promotion of ScienceTokyoJapan
| | - Yukiko Okamura
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
| | - Reizo Baba
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
| | - Kenichi Suijo
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
| | - Masaki Mizuno
- Department of Applied Clinical ResearchUniversity of Texas Southwestern Medical CenterDallasTexasUSA
| | - Jun Sugawara
- Human Informatics and Interaction Research InstituteNational Institute of Advanced Industrial Science and TechnologyTsukubaJapan
| | - Koji Kitatsuji
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
| | - Hisayoshi Ogata
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
| | - Kaoru Toda
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
| | - Norio Hotta
- Graduate School of Life and Health SciencesChubu UniversityKasugaiJapan
- College of Life and Health SciencesChubu UniversityKasugaiJapan
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Samora M, Incognito AV, Vianna LC. Sex differences in blood pressure regulation during ischemic isometric exercise: the role of the β-adrenergic receptors. J Appl Physiol (1985) 2019; 127:408-414. [PMID: 31219771 DOI: 10.1152/japplphysiol.00270.2019] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We sought to investigate whether the β-adrenergic receptors play a pivotal role in sex-related differences in arterial blood pressure (BP) regulation during isometric exercise. Sixteen volunteers (8 women) performed 2 min of ischemic isometric handgrip exercise (IHE) and 2 min of postexercise circulatory occlusion (PECO). Heart rate (HR) and beat-to-beat arterial BP were continuously measured. Beat-to-beat estimates of stroke volume (ModelFlow) were obtained and matched with HR to calculate cardiac output (Q̇) and total peripheral resistance (TPR). Two trials were randomly conducted between placebo and nonselective β-adrenergic blockade (40 mg propranolol). Under the placebo condition, the magnitude of the BP response in IHE was lower in women compared with men. During PECO, the BP remained elevated and the sex differences persisted. The β-blockade attenuated the BP response during IHE in men (∆57 ± 4 vs. ∆45 ± 7 mmHg, P = 0.025) due to a reduction in Q̇ (∆3.7 ± 0.5 vs. ∆1.8 ± 0.2 L/min, P = 0.012) while TPR was not affected. In women, however, the BP response during IHE was unchanged (∆27 ± 3 vs. ∆28 ± 3 mmHg, P = 0.889), despite attenuated Q̇ (∆2.7 ± 0.4 vs. ∆1.3 ± 0.2 L/min, P = 0.012). These responses were mediated by a robust increase in TPR under β-blockade (∆-0.2 ± 0.4 vs. ∆2.2 ± 0.7 mmHg·L-1·min, P = 0.012). These findings demonstrate that the sex differences in arterial BP regulation during ischemic IHE are mediated by β-adrenergic receptors.NEW & NOTEWORTHY We found that the blood pressure response during isometric exercise in women is mediated by increases in cardiac output, whereas in men it is mediated by increases in both cardiac output and total peripheral resistance. In addition, women showed a robust increase in total peripheral resistance under β-blockade during isometric exercise and muscle metaboreflex activation. These findings demonstrate that sex differences in blood pressure regulation during isometric exercise are mediated by β-adrenergic receptors.
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Affiliation(s)
- Milena Samora
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasilia, Distrito Federal, Brazil
| | - Anthony V Incognito
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasilia, Distrito Federal, Brazil.,Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Lauro C Vianna
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasilia, Distrito Federal, Brazil
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Barbosa TC, Kaur J, Stephens BY, Akins JD, Keller DM, Brothers RM, Fadel PJ. Attenuated forearm vascular conductance responses to rhythmic handgrip in young African-American compared with Caucasian-American men. Am J Physiol Heart Circ Physiol 2018; 315:H1316-H1321. [PMID: 30118345 DOI: 10.1152/ajpheart.00387.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Previous studies have demonstrated that African-American (AA) individuals have heightened vasoconstrictor and reduced vasodilator responses under resting conditions compared with Caucasian-American (CA) individuals. However, potential differences in vascular responses to exercise remain unclear. Therefore, we tested the hypothesis that, compared with CA subjects, AA subjects would present an attenuated increase in forearm vascular conductance (FVC) during rhythmic handgrip exercise. Forearm blood flow (FBF; duplex Doppler ultrasound) and mean arterial pressure (MAP; finger photoplethysmography) were measured in healthy young CA ( n = 10) and AA ( n = 10) men during six trials of rhythmic handgrip performed at workloads of 4, 8, 12, 16, 20, and 24 kg. FVC (calculated as FBF/MAP), FBF, and MAP were similar between groups at rest (FVC: 63 ± 7 ml·min-1·100 mmHg-1 in CA subjects vs. 62 ± 7 ml·min-1·100 mmHg-1 in AA subjects, P = 0.862). There was an intensity-dependent increase in FVC during exercise in both groups; however, AA subjects presented lower FVC (interaction P < 0.001) at 8-, 12-, 16-, 20-, and 24-kg workloads (e.g., 24 kg: 324 ± 20 ml·min-1·100 mmHg-1 in CA subjects vs. 241 ± 21 ml·min-1·100 mmHg-1 in AA subjects, P < 0.001). FBF responses to exercise were also lower in AA subjects (interaction P < 0.001), whereas MAP responses did not differ between groups (e.g., ∆MAP at 24 kg: +19 ± 2 mmHg in CA subjects vs. +19 ± 2 mmHg in AA subjects, interaction P = 0.950). These findings indicate lower hyperemic responses to rhythmic handgrip exercise in AA men compared with CA men. NEW & NOTEWORTHY It is known that African-American individuals have heightened vasoconstriction and reduced vasodilation under resting conditions compared with Caucasian-American individuals. Here, we identified that the hyperemic response to moderate and high-intensity rhythmic handgrip exercise was lower in healthy young African-American men.
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Affiliation(s)
- Thales C Barbosa
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
| | - Jasdeep Kaur
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
| | - Brandi Y Stephens
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
| | - John D Akins
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
| | - David M Keller
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
| | - R Matthew Brothers
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
| | - Paul J Fadel
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington , Arlington, Texas
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Spranger MD, Krishnan AC, Levy PD, O'Leary DS, Smith SA. Blood flow restriction training and the exercise pressor reflex: a call for concern. Am J Physiol Heart Circ Physiol 2015; 309:H1440-52. [PMID: 26342064 PMCID: PMC7002872 DOI: 10.1152/ajpheart.00208.2015] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 08/31/2015] [Indexed: 02/07/2023]
Abstract
Blood flow restriction (BFR) training (also known as Kaatsu training) is an increasingly common practice employed during resistance exercise by athletes attempting to enhance skeletal muscle mass and strength. During BFR training, blood flow to the exercising muscle is mechanically restricted by placing flexible pressurizing cuffs around the active limb proximal to the working muscle. This maneuver results in the accumulation of metabolites (e.g., protons and lactic acid) in the muscle interstitium that increase muscle force and promote muscle growth. Therefore, the premise of BFR training is to simulate and receive the benefits of high-intensity resistance exercise while merely performing low-intensity resistance exercise. This technique has also been purported to provide health benefits to the elderly, individuals recovering from joint injuries, and patients undergoing cardiac rehabilitation. Since the seminal work of Alam and Smirk in the 1930s, it has been well established that reductions in blood flow to exercising muscle engage the exercise pressor reflex (EPR), a reflex that significantly contributes to the autonomic cardiovascular response to exercise. However, the EPR and its likely contribution to the BFR-mediated cardiovascular response to exercise is glaringly missing from the scientific literature. Inasmuch as the EPR has been shown to generate exaggerated increases in sympathetic nerve activity in disease states such as hypertension (HTN), heart failure (HF), and peripheral artery disease (PAD), concerns are raised that BFR training can be used safely for the rehabilitation of patients with cardiovascular disease, as has been suggested. Abnormal BFR-induced and EPR-mediated cardiovascular complications generated during exercise could precipitate adverse cardiovascular or cerebrovascular events (e.g., cardiac arrhythmia, myocardial infarction, stroke and sudden cardiac death). Moreover, although altered EPR function in HTN, HF, and PAD underlies our concern for the widespread implementation of BFR, use of this training mechanism may also have negative consequences in the absence of disease. That is, even normal, healthy individuals performing resistance training exercise with BFR are potentially at increased risk for deleterious cardiovascular events. This review provides a brief yet detailed overview of the mechanisms underlying the autonomic cardiovascular response to exercise with BFR. A more complete understanding of the consequences of BFR training is needed before this technique is passively explored by the layman athlete or prescribed by a health care professional.
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Affiliation(s)
- Marty D Spranger
- Department of Physiology, Michigan State University, East Lansing, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan;
| | - Abhinav C Krishnan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan
| | - Phillip D Levy
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Emergency Medicine, Wayne State University School of Medicine, Detroit, Michigan
| | - Donal S O'Leary
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan
| | - Scott A Smith
- Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
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Cardiovascular Reflexes Activity and Their Interaction during Exercise. BIOMED RESEARCH INTERNATIONAL 2015; 2015:394183. [PMID: 26557662 PMCID: PMC4628760 DOI: 10.1155/2015/394183] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 07/26/2015] [Accepted: 07/28/2015] [Indexed: 02/07/2023]
Abstract
Cardiac output and arterial blood pressure increase during dynamic exercise notwithstanding the exercise-induced vasodilation due to functional sympatholysis. These cardiovascular adjustments are regulated in part by neural reflexes which operate to guarantee adequate oxygen supply and by-products washout of the exercising muscles. Moreover, they maintain adequate perfusion of the vital organs and prevent excessive increments in blood pressure. In this review, we briefly summarize neural reflexes operating during dynamic exercise with particular emphasis on their interaction.
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Nobrega ACL, O'Leary D, Silva BM, Marongiu E, Piepoli MF, Crisafulli A. Neural regulation of cardiovascular response to exercise: role of central command and peripheral afferents. BIOMED RESEARCH INTERNATIONAL 2014; 2014:478965. [PMID: 24818143 PMCID: PMC4000959 DOI: 10.1155/2014/478965] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 02/04/2014] [Indexed: 12/12/2022]
Abstract
During dynamic exercise, mechanisms controlling the cardiovascular apparatus operate to provide adequate oxygen to fulfill metabolic demand of exercising muscles and to guarantee metabolic end-products washout. Moreover, arterial blood pressure is regulated to maintain adequate perfusion of the vital organs without excessive pressure variations. The autonomic nervous system adjustments are characterized by a parasympathetic withdrawal and a sympathetic activation. In this review, we briefly summarize neural reflexes operating during dynamic exercise. The main focus of the present review will be on the central command, the arterial baroreflex and chemoreflex, and the exercise pressure reflex. The regulation and integration of these reflexes operating during dynamic exercise and their possible role in the pathophysiology of some cardiovascular diseases are also discussed.
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Affiliation(s)
- Antonio C. L. Nobrega
- Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, RJ, Brazil
| | - Donal O'Leary
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Bruno Moreira Silva
- Section of Exercise Physiology, Department of Physiology, Federal University of São Paulo, SP, Brazil
| | - Elisabetta Marongiu
- Sports Physiology laboratory Lab., Department of Medical Sciences, University of Cagliari, Italy
| | - Massimo F. Piepoli
- Heart Failure Unit, Cardiac Department, Guglielmo da Saliceto Polichirurgico Hospital, Piacenza, Italy
| | - Antonio Crisafulli
- Sports Physiology laboratory Lab., Department of Medical Sciences, University of Cagliari, Italy
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Karcher JR, Greene AS. Bone marrow mononuclear cell angiogenic competency is suppressed by a high-salt diet. Am J Physiol Cell Physiol 2013; 306:C123-31. [PMID: 24259418 DOI: 10.1152/ajpcell.00164.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Autologous bone marrow-derived mononuclear cell (BM-MNC) transplantation is a potential therapy for inducing revascularization in ischemic tissues providing the underlying disease process had not negatively affected BM-MNC function. Previously, we have shown that skeletal muscle angiogenesis induced by electrical stimulation is impaired by a high-salt diet (HSD; 4% NaCl) in Sprague-Dawley (SD) rats. In this study we tested the hypothesis that BM-MNC angiogenic function is impaired by an elevated dietary sodium intake. Following 1 wk on HSD, either vehicle or BM-MNCs derived from SD donor rats on HSD or normal salt diet (NSD; 0.4% NaCl) were injected into male SD rats undergoing hindlimb stimulation. Administration of BM-MNCs (intramuscular or intravenous) from NSD donors, but not HSD donors, restored the angiogenic response in HSD recipients. Angiotensin II (3 ng · kg(-1) · min(-1)) infusion of HSD donor rats restored angiogenic capacity of BM-MNCs, and treatment of NSD donor rats with losartan, an angiotensin II receptor-1 antagonist, inhibited BM-MNC angiogenic competency. HSD BM-MNCs and NSD losartan BM-MNCs exhibited increased apoptosis in vitro following an acute 6-h hypoxic stimulus. HSD BM-MNCs also had increased apoptosis following injection into skeletal muscle. This study suggests that BM-MNC transplantation can restore skeletal muscle angiogenesis and that HSD impairs the angiogenic competency of BM-MNCs due to suppression of the renin-angiotensin system causing increased apoptosis.
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Affiliation(s)
- Jamie R Karcher
- Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin; and
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Abstract
Skeletal muscle fatigue is defined as the fall of force or power in response to contractile activity. Both the mechanisms of fatigue and the modes used to elicit it vary tremendously. Conceptual and technological advances allow the examination of fatigue from the level of the single molecule to the intact organism. Evaluation of muscle fatigue in a wide range of disease states builds on our understanding of basic function by revealing the sources of dysfunction in response to disease.
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Affiliation(s)
- Jane A Kent-Braun
- Department of Kinesiology, University of Massachusetts-Amherst, Amherst, Massachusetts, USA.
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Muller MD, Drew RC, Cui J, Blaha CA, Mast JL, Sinoway LI. Effect of oxidative stress on sympathetic and renal vascular responses to ischemic exercise. Physiol Rep 2013; 1. [PMID: 24098855 PMCID: PMC3787721 DOI: 10.1002/phy2.47] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Reactive oxygen species (ROS), produced acutely during skeletal muscle contraction, are known to stimulate group IV muscle afferents and accentuate the exercise pressor reflex (EPR) in rodents. The effect of ROS on the EPR in humans is unknown. We conducted a series of studies using ischemic fatiguing rhythmic handgrip to acutely increase ROS within skeletal muscle, ascorbic acid infusion to scavenge free radicals, and hyperoxia inhalation to further increase ROS production. We hypothesized that ascorbic acid would attenuate the EPR and that hyperoxia would accentuate the EPR. Ten young healthy subjects participated in two or three experimental trials on separate days. Beat-by-beat measurements of heart rate (HR), mean arterial pressure (MAP), muscle sympathetic nerve activity (MSNA), and renal vascular resistance index (RVRI) were measured and compared between treatments (saline and ascorbic acid; room air and hyperoxia). At fatigue, the reflex increases in MAP (31 ± 3 versus 29 ± 2 mmHg), HR (19 ± 3 versus 20 ± 3 bpm), MSNA burst rate (21 ± 4 versus 23 ± 4 burst/min), and RVRI (39 ± 12 versus 44 ± 13%) were not different between saline and ascorbic acid. Relative to room air, hyperoxia did not augment the reflex increases in MAP, HR, MSNA, or RVRI in response to exercise. Muscle metaboreflex activation and time/volume control experiments similarly showed no treatment effects. While contrary to our initial hypotheses, these findings suggest that ROS do not play a significant role in the normal reflex adjustments to ischemic exercise in young healthy humans.
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Affiliation(s)
- Matthew D Muller
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, 500 University Drive, Hershey, PA 17033
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Spranger MD, Sala-Mercado JA, Coutsos M, Kaur J, Stayer D, Augustyniak RA, O'Leary DS. Role of cardiac output versus peripheral vasoconstriction in mediating muscle metaboreflex pressor responses: dynamic exercise versus postexercise muscle ischemia. Am J Physiol Regul Integr Comp Physiol 2013; 304:R657-63. [PMID: 23427084 DOI: 10.1152/ajpregu.00601.2012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscle metaboreflex activation (MMA) during submaximal dynamic exercise in normal individuals increases mean arterial pressure (MAP) via increases in cardiac output (CO) with little peripheral vasoconstriction. The rise in CO occurs primarily via increases in heart rate (HR) with maintained or slightly increased stroke volume. When the reflex is sustained during recovery (postexercise muscle ischemia, PEMI), HR declines yet MAP remains elevated. The role of CO in mediating the pressor response during PEMI is controversial. In seven chronically instrumented canines, steady-state values with MMA during mild exercise (3.2 km/h) were observed by reducing hindlimb blood flow by ~60% for 3-5 min. MMA during exercise was followed by 60 s of PEMI. Control experiments consisted of normal exercise and recovery. MMA during exercise increased MAP, HR, and CO by 55.3 ± 4.9 mmHg, 42.5 ± 6.9 beats/min, and 2.5 ± 0.4 l/min, respectively. During sustained MMA via PEMI, MAP remained elevated and CO remained well above the normal recovery levels. Neither MMA during dynamic exercise nor during PEMI significantly affected peripheral vascular conductance. We conclude that the sustained increase in MAP during PEMI is driven by a sustained increase in CO not peripheral vasoconstriction.
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Affiliation(s)
- Marty D Spranger
- Department of Physiology and The Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, MI 48201, USA
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Booghs C, Baudry S, Enoka R, Duchateau J. Influence of neural adjustments and muscle oxygenation on task failure during sustained isometric contractions with elbow flexor muscles. Exp Physiol 2012; 97:918-29. [DOI: 10.1113/expphysiol.2011.064303] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Mendez-Villanueva A, Landaluce JP, García BF, Terrados N, Bishop D. Inaccuracy of the HR reserve vs. V˙O2 reserve relationship during prone arm-paddling exercise in surfboard riders. J Physiol Anthropol 2010; 29:189-95. [PMID: 21139320 DOI: 10.2114/jpa2.29.189] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Previous studies have demonstrated that during lower-body exercise the percentage of heart rate reserve (%HRR) is equivalent to the percentage of the oxygen consumption reserve (%V˙O(2R)) but not to a percentage of the peak oxygen consumption (%V˙O(2peak)). The current study examined these relationships in trained surfboard riders (surfers) during upper-body exercise. Thirteen well-trained competitive surfers performed a stepwise, incremental, prone arm-paddling exercise test to exhaustion. For each subject, data obtained at the end of each stage (i.e., HR and V˙O(2) values) were expressed as a percentage of HRR, V˙O(2peak), and V˙O(2R) respectively and used to determine the individual %HRR-%V˙O(2peak) and %HRR-%V˙O(2R) relationships. Mean slope and intercept were calculated and compared with the line of identity (slope=1, intercept=0). The %HRR versus %V˙O(2R) regression mean slope (0.88±0.06) and intercept (20.82±4.57) were significantly different (p<0.05) from 1 and 0, respectively. Similarly, the regression of %HRR versus %V˙O(2peak) resulted in a line that differed in the slope (p<0.05) but not in the intercept (p=0.94) from the line of identity. Predicted values of %HRR were significantly higher (p<0.05) from indicated values of %V˙O(2R) for all the intensities ranging from 35% to 95% V˙O(2R). Unlike results found for lower-body exercise, a given %HRR during prone upper-body exercise was not equivalent to its corresponding %V˙O(2R). Thus, to ensure more targeted exercise intensity during arm-paddling exercise, individual HR-V˙O(2) equations should be used.
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Draper N, Jones GA, Fryer S, Hodgson CI, Blackwell G. Physiological and psychological responses to lead and top rope climbing for intermediate rock climbers. Eur J Sport Sci 2010. [DOI: 10.1080/17461390903108125] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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McCord JL, Tsuchimochi H, Kaufman MP. Acid-sensing ion channels contribute to the metaboreceptor component of the exercise pressor reflex. Am J Physiol Heart Circ Physiol 2009; 297:H443-9. [PMID: 19465550 DOI: 10.1152/ajpheart.00328.2009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The exercise pressor reflex is evoked by both mechanical and metabolic stimuli arising in contracting skeletal muscle. Recently, the blockade of acid-sensing ion channels (ASICs) with amiloride and A-316567 attenuated the reflex. Moreover, amiloride had no effect on the mechanoreceptor component of the reflex, prompting us to determine whether ASICs contributed to the metaboreceptor component of the exercise pressor reflex. The metaboreceptor component can be assessed by measuring mean arterial pressure during postcontraction circulatory occlusion when only the metaboreceptors are stimulated. We examined the effects of amiloride (0.5 microg/kg), A-317567 (10 mM, 0.5 ml), and saline (0.5 ml) on the pressor response to and after static contraction while the circulation was occluded in 30 decerebrated cats. Amiloride (n = 11) and A-317567 (n = 7), injected into the arterial supply of the triceps surae muscles, attenuated the pressor responses both to contraction while the circulation was occluded and to postcontraction circulatory occlusion (all, P < 0.05). Saline (n = 11), however, had no effect on the pressor responses to contraction while the circulation was occluded or to postcontraction circulatory occlusion (both, P > 0.79). Our findings led us to conclude that ASICs contribute to the metaboreceptor component of the exercise pressor reflex.
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Affiliation(s)
- Jennifer L McCord
- Pennsylvania State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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Momen A, Cui J, McQuillan P, Sinoway LI. Local prostaglandin blockade attenuates muscle mechanoreflex-mediated renal vasoconstriction during muscle stretch in humans. Am J Physiol Heart Circ Physiol 2008; 294:H2184-90. [PMID: 18326807 DOI: 10.1152/ajpheart.00948.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During exercise, muscle mechanoreflex-mediated sympathoexcitation evokes renal vasoconstriction. Animal studies suggest that prostaglandins generated within the contracting muscle sensitize muscle mechanoreflexes. Thus we hypothesized that local prostaglandin blockade would attenuate renal vasoconstriction during ischemic muscle stretch. Eleven healthy subjects performed static handgrip before and after local prostaglandin blockade (6 mg ketorolac tromethamine infused into the exercising forearm) via Bier block. Renal blood flow velocity (RBV; Duplex Ultrasound), mean arterial pressure (MAP; Finapres), and heart rate (HR; ECG) were obtained during handgrip, post-handgrip muscle ischemia (PHGMI) followed by PHGMI with passive forearm muscle stretch (PHGMI + stretch). Renal vascular resistance (RVR, calculated as MAP/RBV) was increased from baseline during all paradigms except during PHGMI + stretch after the ketorolac Bier block trial where RVR did not change from baseline. Before Bier block, RVR rose more during PHGMI + stretch than during PHGMI alone (P < .01). Similar results were found after a saline Bier block trial (Delta53 +/- 13% vs. Delta35 +/- 10%; P < 0.01). However, after ketorolac Bier block, RVR was not greater during PHGMI + stretch than during PHGMI alone [Delta39 +/- 8% vs. Delta40 +/- 12%; P = not significant (NS)]. HR and MAP responses were similar during PHGMI and PHGMI + stretch (P = NS). Passive muscle stretch during ischemia augments renal vasoconstriction, suggesting that ischemia sensitizes mechanically sensitive afferents. Inhibition of prostaglandin synthesis eliminates this mechanoreceptor sensitization-mediated constrictor responses. Thus mechanoreceptor sensitization in humans is linked to the production of prostaglandins.
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Affiliation(s)
- Afsana Momen
- Heart & Vascular Inst.itute, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA
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Stewart JM, Taneja I, Medow MS. Reduced central blood volume and cardiac output and increased vascular resistance during static handgrip exercise in postural tachycardia syndrome. Am J Physiol Heart Circ Physiol 2007; 293:H1908-17. [PMID: 17616747 PMCID: PMC4511486 DOI: 10.1152/ajpheart.00439.2007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Postural tachycardia syndrome (POTS) is characterized by exercise intolerance and sympathoactivation. To examine whether abnormal cardiac output and central blood volume changes occur during exercise in POTS, we studied 29 patients with POTS (17-29 yr) and 12 healthy subjects (18-27 yr) using impedance and venous occlusion plethysmography to assess regional blood volumes and flows during supine static handgrip to evoke the exercise pressor reflex. POTS was subgrouped into normal and low-flow groups based on calf blood flow. We examined autonomic effects with variability techniques. During handgrip, systolic blood pressure increased from 112 +/- 4 to 139 +/- 9 mmHg in control, from 119 +/- 6 to 143 +/- 9 in normal-flow POTS, but only from 117 +/- 4 to 128 +/- 6 in low-flow POTS. Heart rate increased from 63 +/- 6 to 82 +/- 4 beats/min in control, 76 +/- 3 to 92 +/- 6 beats/min in normal-flow POTS, and 88 +/- 4 to 100 +/- 6 beats/min in low-flow POTS. Heart rate variability and coherence markedly decreased in low-flow POTS, indicating uncoupling of baroreflex heart rate regulation. The increase in central blood volume with handgrip was absent in low-flow POTS and blunted in normal-flow POTS associated with abnormal splanchnic emptying. Cardiac output increased in control, was unchanged in low-flow POTS, and was attenuated in normal-flow POTS. Total peripheral resistance was increased compared with control in all POTS. The exercise pressor reflex was attenuated in low-flow POTS. While increased cardiac output and central blood volume characterizes controls, increased peripheral resistance with blunted or eliminated in central blood volume increments characterizes POTS and may contribute to exercise intolerance.
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Affiliation(s)
- Julian M Stewart
- Department of Pediatrics, New York Medical College, Valhalla, New York, USA.
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Gao Z, Li JD, Sinoway LI, Li J. Effect of muscle interstitial pH on P2X and TRPV1 receptor-mediated pressor response. J Appl Physiol (1985) 2007; 102:2288-93. [PMID: 17379752 DOI: 10.1152/japplphysiol.00161.2007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of purinergic P2X receptors and transient receptor potential vanilloid type 1 (TRPV1) on muscle afferent nerve evokes the pressor response. Because P2X and TRPV1 receptors are sensitive to changes in pH, the aim of this study was to examine the effects of muscle acidification on those receptor-mediated cardiovascular responses. In decerebrate rats, the pH in the hindlimb muscle was adjusted by infusing acidic Ringer solutions into the femoral artery. Dialysate was then collected using microdialysis probes inserted into the muscles, and pH was measured. The interstitial pH was 7.53+/-0.01, 7.22+/-0.02, 6.94+/-0.04, and 6.59+/-0.03 in response to arterial infusion of the Ringer solution at pH 7.4, 6.5, 5.5, and 4.5, respectively. Femoral arterial injection of alpha,beta-methylene-ATP (P2X receptor agonist) in the concentration of 0.25 mM (volume, 0.15-0.25 ml; injection duration, 1 min) at the infused pH of 7.4, 6.5, and 5.5 increased mean arterial pressure (MAP) by 29+/-2, 24+/-3, and 21+/-3 mmHg, respectively (P<0.05, pH 5.5 vs. pH 7.4). When pH levels in the infused solution were 7.4, 6.5, 5.5, and 4.5, capsaicin (1 microg/kg), a TRPV1 agonist, was injected into the artery. This elevated MAP by 29+/-4, 33+/-2, 35+/-3, and 40+/-3 mmHg, respectively (P<0.05, pH 4.5 vs. pH 7.4). Furthermore, blocking acid-sensing ion channel (ASIC) blunted pH effects on TRPV1 response. Our data indicate that 1) muscle acidosis attenuates P2X-mediated pressor response but enhances TRPV1 response; 2) exaggerated TRPV1 response may require lower pH in muscle, and the effect is likely to be mediated via ASIC mechanisms. This study provides evidence that muscle pH may be important in modulating P2X and TRPV1 responsiveness in exercising muscle.
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Affiliation(s)
- Zhaohui Gao
- Heart and Vascular Institute H047, Penn State College of Medicine, Milton S. Hershey Medical Center, 500 University Dr., Hershey, PA 17033, USA
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Kuroko Y, Tokunaga N, Yamazaki T, Akiyama T, Ishino K, Sano S, Mori H. Effect of sustained limb ischemia on norepinephrine release from skeletal muscle sympathetic nerve endings. Neurochem Int 2006; 49:448-53. [PMID: 16632086 DOI: 10.1016/j.neuint.2006.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2005] [Accepted: 03/02/2006] [Indexed: 11/21/2022]
Abstract
Acute ischemia has been reported to impair sympathetic outflow distal to the ischemic area in various organs, whereas relatively little is known about this phenomenon in skeletal muscle. We examined how acute ischemia affects norepinephrine (NE) release at skeletal muscle sympathetic nerve endings. We implanted a dialysis probe into the adductor muscle in anesthetized rabbits and measured dialysate NE levels as an index of skeletal muscle interstitial NE levels. Regional ischemia was introduced by microsphere injection and ligation of the common iliac artery. The time courses of dialysate NE levels were examined during prolonged ischemia. Ischemia induced a decrease in the dialysate NE level (from 19+/-4 to 2.0+/-0 pg/ml, mean+/-S.E.), and then a progressive increase in the dialysate NE level. The increment in the dialysate NE level was examined with local administration of desipramine (DMI, a membrane NE transport inhibitor), omega-conotoxin GVIA (CTX, an N-type Ca(2+) channel blocker), or TMB-8 (an intracellular Ca(2+) antagonist). At 4h ischemia, the increment in the dialysate NE level (vehicle group, 143+/-30 pg/ml) was suppressed by TMB-8 (25+/-5 pg/ml) but not by DMI (128+/-10 pg/ml) or CTX (122+/-18 pg/ml). At 6h ischemia, the increment in the dialysate NE level was not suppressed by the pretreatment. Ischemia induced biphasic responses in the skeletal muscle. Initial reduction of NE release may be mediated by an impairment of axonal conduction and/or NE release function, while in the later phase, the skeletal muscle ischemia-induced NE release was partly attributable to exocytosis via intracellular Ca(2+) overload rather than opening of calcium channels or carrier mediated outward transport of NE.
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Affiliation(s)
- Yosuke Kuroko
- Department of Cardiovascular Surgery, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan
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Stewart JM, Montgomery LD, Glover JL, Medow MS. Changes in regional blood volume and blood flow during static handgrip. Am J Physiol Heart Circ Physiol 2006; 292:H215-23. [PMID: 16936003 PMCID: PMC4511502 DOI: 10.1152/ajpheart.00681.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increased blood pressure (BP) and heart rate during exercise characterizes the exercise pressor reflex. When evoked by static handgrip, mechanoreceptors and metaboreceptors produce regional changes in blood volume and blood flow, which are incompletely characterized in humans. We studied 16 healthy subjects aged 20-27 yr using segmental impedance plethysmography validated against dye dilution and venous occlusion plethysmography to noninvasively measure changes in regional blood volumes and blood flows. Static handgrip while in supine position was performed for 2 min without postexercise ischemia. Measurements of heart rate and BP variability and coherence analyses were used to examine baroreflex-mediated autonomic effects. During handgrip exercise, systolic BP increased from 120 +/- 10 to 148 +/- 14 mmHg, whereas heart rate increased from 60 +/- 8 to 82 +/- 12 beats/min. Heart rate variability decreased, whereas BP variability increased, and transfer function amplitude was reduced from 18 +/- 2 to 8 +/- 2 ms/mmHg at low frequencies of approximately 0.1 Hz. This was associated with marked reduction of coherence between BP and heart rate (from 0.76 +/- 0.10 to 0.26 +/- 0.05) indicative of uncoupling of heart rate regulation by the baroreflex. Cardiac output increased by approximately 18% with a 4.5% increase in central blood volume and an 8.5% increase in total peripheral resistance, suggesting increased cardiac preload and contractility. Splanchnic blood volume decreased reciprocally with smaller decreases in pelvic and leg volumes, increased splanchnic, pelvic and calf peripheral resistance, and evidence for splanchnic venoconstriction. We conclude that the exercise pressor reflex is associated with reduced baroreflex cardiovagal regulation and driven by increased cardiac output related to enhanced preload, cardiac contractility, and splanchnic blood mobilization.
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Affiliation(s)
- Julian M Stewart
- Professor of Pediatrics and Physiology, Research Division and Hypotension Laboratory, New York Medical College, Suite 3050, 19 Bradhurst Ave., Hawthorne, NY 10532, USA.
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Crisafulli A, Salis E, Pittau G, Lorrai L, Tocco F, Melis F, Pagliaro P, Concu A. Modulation of cardiac contractility by muscle metaboreflex following efforts of different intensities in humans. Am J Physiol Heart Circ Physiol 2006; 291:H3035-42. [PMID: 16782848 DOI: 10.1152/ajpheart.00221.2006] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Accumulation of metabolic end products within skeletal muscle stimulates sensory nerves, thus evoking a pressor response termed "metaboreflex." The aim of this study was to evaluate changes in hemodynamics occurring during metaboreflex activation obtained by postexercise muscle ischemia (PEMI) after two different exercise intensities. In twelve healthy subjects, the metaboreflex was studied with the PEMI method at the start of recovery from one leg-dynamic knee extension performed at intensities of 30% (PEMI 30%) and 70% (PEMI 70%) of the maximum workload achieved in a preliminary test. Control exercise recovery tests at the same intensities were also conducted. Central hemodynamics were evaluated by means of impedance cardiography. The main findings were that 1) during metaboreflex, exercise conducted against the higher workload caused a more pronounced blood pressure increase than the strain conducted against the lower workload; and 2) during PEMI 70%, this blood pressure response was mainly achieved through enhancement of myocardial contractility that increased stroke volume and, in turn, cardiac output, whereas during PEMI 30%, the blood pressure response was reached predominantly by means of vasoconstriction. Thus a substantial enhancement of myocardial contractility was reached only in the PEMI 70% test. These results suggest that hemodynamic regulation during metaboreflex engagement caused by PEMI in humans is dependent on the intensity of the previous effort. Moreover, the cardiovascular response during metaboreflex is not merely achieved by vasoconstriction alone, but it appears that there is a complex interplay between peripheral vasoconstriction and heart contractility recruitment.
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Affiliation(s)
- Antonio Crisafulli
- Dept. of Science Applied to Biological Systems, University of Cagliari, 09124 Cagliari, Italy.
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