Effects of exercise training on thermoregulatory responses and blood volume in older men

Effects of individual characteristics and local body functions on sweating response: A review

In this study, we conducted a literature review to deepen our understanding of the sweating response of the thermoregulatory system, focusing on the influence of individual characteristics and local body functions. Among the factors related to individual characteristics, improvement in aerobic fitness had a positive effect on the sweating response, whereas aging exerted an inhibitory effect. Short-term artificial acclimation and seasonal heat acclimatization promoted sweating, whereas long-term geographical acclimatization suppressed sweating. Male exhibited higher sweat rates than female when the metabolic heat production was high. Individuals with smaller surface area-to-mass ratios tended to have higher sweat rates than those with larger ratios. Regarding local body functions, sweat distribution in the resting state showed high regional sweat rates in the lower limbs and torso, with higher values in the lower limbs when in the supine position and higher values in the torso when in the seated position. During exercise, the regional sweat rates was high in the torso, whereas the limbs exhibited relatively low sweat rates. These differences in sweat distribution stem from the thermoregulatory potential of each body region, which aims to efficiently regulate body temperature. Local effects have only been examined in the thigh and forearm, with temperature coefficient Q10 ranging from 2 to 5. Only the forehead showed significantly high thermosensitivity among all body regions.

Comparison of daily heart rate and heart rate variability in trained and sedentary aged horses

Athletic horses are usually retired from equestrian competition at an advanced age. Aged horses may then continue to have regular exercise or are sedentary. The comparison of autonomic regulation between sedentary aged horses (SAH) and trained aged horses (TAH) after retirement remains unpublished. This study compared daily heart rate (HR) and heart rate variability between 11 SAH and 11 TAH over 22 h (07.00 h to 05.00 h on an alternate day) and during the day and night. An increase in mean beat-to-beat (RR) intervals (p < 0.01-0.0001) and parasympathetic nervous system (PNS) index (p < 0.05-0.0001), corresponding to the decreased HR and sympathetic nervous system (SNS) index (p < 0.01-0.0001), was observed at night. Compared to SAH, lowered mean HR and SNS index, corresponding to elevated mean RR intervals and very-low-frequency bands, were marked in TAH during the day (p < 0.05 for all variables). Whereas the standard deviation of the RR intervals index was higher in TAH than in SAH during the day and night (p < 0.05 for both periods). It was suggested that aged horses with different physical activities revealed distinct autonomic responses. TAH demonstrated higher HRV than SAH during the day. A decreased HR in TAH is prone to result from a reduced SNS role, leading to a shift toward more PNS activity during the day. More research is warranted to determine to what extent the autonomic regulation is modulated by accompanying higher exercise volume or programmed exercise in aged horses.

Experimental research in environmentally induced hyperthermic older persons: A systematic quantitative literature review mapping the available evidence

The heat-related health burden is expected to persist and worsen in the coming years due to an aging global population and climate change. Defining the breadth and depth of our understanding of age-related changes in thermoregulation can identify underlying causes and strategies to protect vulnerable individuals from heat. We conducted the first systematic quantitative literature review to provide context to the historical experimental research of healthy older adults - compared to younger adults or unhealthy age matched cases - during exogenous heat strain, focusing on factors that influence thermoregulatory function (e.g. co-morbidities). We identified 4,455 articles, with 147 meeting eligibility criteria. Most studies were conducted in the US (39%), Canada (29%), or Japan (12%), with 71% of the 3,411 participants being male. About 71% of the studies compared younger and older adults, while 34% compared two groups of older adults with and without factors influencing thermoregulation. Key factors included age combined with another factor (23%), underlying biological mechanisms (18%), age independently (15%), influencing health conditions (15%), adaptation potential (12%), environmental conditions (9%), and therapeutic/pharmacological interventions (7%). Our results suggest that controlled experimental research should focus on the age-related changes in thermoregulation in the very old, females, those with overlooked chronic heat-sensitive health conditions (e.g. pulmonary, renal, mental disorders), the impact of multimorbidity, prolonged and cumulative effects of extreme heat, evidence-based policy of control measures (e.g. personal cooling strategies), pharmaceutical interactions, and interventions stimulating protective physiological adaptation. These controlled studies will inform the directions and use of limited resources in ecologically valid fieldwork studies.

Resistance training and inter-interindividual response differences on cardiorespiratory fitness in older adults: An ancillary meta-analysis of randomized controlled trials

Examine true inter-individual response differences (IIRD) as a result of resistance training on cardiorespiratory fitness in older adults. Data from a recent meta-analysis of 22 randomized controlled trials representing 552 men and women (292 resistance training, 260 control) ≥ 60 years of age were included. The primary outcome was cardiorespiratory fitness (VO2max) in ml.kg-1.min-1. Using the inverse variance heterogeneity (IVhet) model, statistically significant treatment effect (resistance training minus control) increases in VO2max in ml.kg-1.min-1 were found (mean, 1.8, 95% CI, 0.4 to 3.3 ml.kg-1.min-1, p = 0.01; Q = 82.8, p < 0.001; I2 = 74.6%, 95% CI, 61.6 to 83.3%; τ 2 =1.1). The 95% prediction interval (PI) was -0.8 to 4.5 ml.kg-1.min-1. However, no statistically significant IIRD was observed (mean, 0.6, 95% CI, -1.1 to 1.4 ml.kg-1.min-1; τ 2 =1.5). The 95% PI was -1.8 to 2.0 ml.kg-1.min-1. In conclusion, while progressive resistance training may increase VO2max in ml.kg-1.min-1, a lack of true resistance-training-associated IIRD exist.

Relatively minor influence of individual characteristics on critical wet-bulb globe temperature (WBGT) limits during light activity in young adults (PSU HEAT Project)

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.

Wirkmechanismen körperlicher Aktivität auf den Schlaf bei Patienten mit Depression: Ein Narratives Review

Insomnie ist eines der Kardinalsymptome einer unipolaren Depression. Insomnie hat dabei einen negativen Einfluss auf den Krankheitsverlauf, ist eines der häufigsten Residualsymptome und ein Risikofaktor für ein Rezidiv. Im vorliegenden Überblick werden mögliche Wirkmechanismen von körperlichem Training auf den Schlaf bei Patienten mit Depression zusammengefasst. Die vorgestellten Mechanismen beruhen auf Daten aus In-vitro‑, Tier- und Humanstudien, welche die Effekte von Kraft‑, Ausdauer- und Mind-Body-Training untersuchen. Sowohl akutes Training als auch über mehrere Wochen regelmäßig absolviertes Training kann über verschiedene Signalwege positive Effekte auf den Schlaf bei Patienten mit Depression haben. Folgende Mechanismen sind dabei relevant: Zeitgebereffekte, Energiekonservierung, Regeration, Thermoregulation, psychophysiologische Effekte und „tissue–brain crosstalk“. Diese Befunde sind relevant, um die Therapie von nichtorganischen Schlafstörungen im Rahmen einer depressiven Episode besser zu verstehen, weiterzuentwickeln und auf individuelle Patienten anzupassen.

Human temperature regulation under heat stress in health, disease, and injury

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Heat exposure limits for young unacclimatized males and females at low and high humidity

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 (WBGT_crit), 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% V̇O_2max in a controlled environmental chamber. Progressive heat stress exposures were performed with either (1) constant dry-bulb temperature (T_db) of 34 and 36 °C and increasing ambient water vapor pressure (P_a) (P_crit trials; WH); or (2) constant P_a of 12 and 16 mmHg and increasing T_db (T_crit trials; HD). Chamber T_db and P_a, and subject esophageal temperature (T_es), 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 T_es was observed. Absolute WBGT_crit and WBGT_crit adjusted to a metabolic rate of 300 W (WBGT₃₀₀), and the difference between WBGT_crit and occupational exposure limits (OEL; ΔOEL) was assessed. WBGT_crit, 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). WBGT_crit 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, V̇O_2max was not associated with WBGT₃₀₀ or ΔOEL for either sex (r ≤ 0.12, p ≥ 0.49). These findings suggest that WBGT_crit is higher in females compared to males in WH, but not HD, conditions. Additionally, the WBGT_crit is lower in females, but not males, in HD compared to WH conditions.

The role of resistance exercise training for improving cardiorespiratory fitness in healthy older adults: a systematic review and meta-analysis

BACKGROUND

Declines in cardiorespiratory fitness (CRF) and muscle mass are both associated with advancing age and each of these declines is associated with worse health outcomes. Resistance exercise training (RET) has previously been shown to improve muscle mass and function in the older population. If RET is also able to improve CRF, as it has been shown to do in younger populations, it has the potential to improve multiple health outcomes in the expanding older population.

METHODS

This systematic review aimed to identify the role of RET for improving CRF in healthy older adults. A search across CINAHL, MEDLINE, EMBASE and EMCARE databases was conducted with meta-analysis performed on eligible papers to identify improvements in established CRF parameters (VO2 peak, aerobic threshold (AT), 6-minute walking distance test (6MWT) following RET intervention. Main eligibility criteria included older adults (aged over 60), healthy cohorts (disease-specific cohorts were excluded) and RET intervention.

RESULTS

Thirty-seven eligible studies were identified. Meta-analysis revealed a significant improvement in VO2 peak (MD 1.89 ml/kg/min; 95% confidence interval (CI) 1.21-2.57 ml/kg/min), AT (MD 1.27 ml/kg/min; 95% CI 0.44-2.09 ml/kg/min) and 6MWT (MD 30.89; 95% CI 26.7-35.08) in RET interventions less than 24 weeks. There was no difference in VO2 peak or 6MWT in interventions longer than 24 weeks.

DISCUSSION

This systematic review adds to a growing body of evidence supporting the implementation of RET in the older population for improving whole-body health, particularly in time-limited timeframes.

Effects of Yogurt Intake on Cardiovascular Strain during Outdoor Interval Walking Training by Older People in Midsummer: A Randomized Controlled Study

We examined whether post-exercise yogurt intake reduced cardiovascular strain during outdoor interval walking training (IWT) in older people during midsummer. The IWT is a training regimen repeating slow and fast walking at ~40% and ≥70% peak aerobic capacity, respectively, for 3 min each per set, ≥5 sets per day, and ≥4 days/wk. We randomly divided 28 male and 75 female older people (~73 yr), who had performed IWT ≥12 months, into a carbohydrate group (CHO-G) consuming jelly (45 g CHO, 180 kcal) and a yogurt group (YGT-G) consuming a yogurt drink (9.3 g protein, 39 g CHO, 192 kcal) immediately after daily IWT for 56 days while monitoring exercise intensity and heart rate (HR) with portable devices. We analyzed the results in 39 subjects for the CHO-G and 37 subjects for the YGT-G who performed IWT ≥ 4 days/wk, ≥60 min total fast walking/wk, and ≥4 sets of each walk/day. We found that the mean HR for fast walking decreased significantly from the baseline after the 30th day in the YGT-G (p < 0.03), but not in the CHO-G (p = 1.00). There were no significant differences in training achievements between the groups. Thus, post-exercise yogurt intake might reduce cardiovascular strain during outdoor walking training in older people.

New Portable Device for Continuous Measurement of Sweat Rate under Heat Stress during Field Tests

We have developed a portable method to measure sweat rate (SR) under heat stress during field tests. We randomly divided 15 males and 17 females (23-78years) into a group (EG) to determine an equation to convert a unit of SR (mmHg) by the portable method to that (mg·min^-1·cm^-2) by the ventilation method, and another group (VG) to validate the equation. Since we repeated measurements twice in three subjects, we randomly assigned the two measurements to one of the two groups and analyzed the results in 18 and 17 subjects for EG and VG, respectively. Subjects cycled for 20 min at moderate intensity in a warm environment while chest SR was simultaneously measured with a capsule installed with 4.8g of silica gel and two microfans (8.4cm³ volume) and with another capsule (12.6cm² area) ventilated with dry air at 1.5l·min^-1. Since the esophageal temperature (T_es) threshold for increasing SR and the slope of SR at a given increase in T_es by the portable method (x) were in high agreement with those values obtained by the ventilation method (y) in both groups (all, r>0.88, P<0.001), we determined regression equations for all subjects after pooling data from both groups: y=1.11x-3.99 and y=1.05x+0.01 when the 95% prediction limits were ±0.12°C and ±0.43 mg·min^-1·cm^-2·°C^-1 with minimum mean differences over the range of 36.2 to 37.2°C and 0.2 to 2.4 mg·min^-1·cm^-2·°C^-1, respectively, using Bland-Altman analysis. Based on these findings, we consider the portable device to be reliable enough to evaluate individual sweating capacity during field tests.

Three-week exercise and protein intake immediately after exercise increases the 6-min walking distance with simultaneously improved plasma volume in patients with chronic cerebrovascular disease: a preliminary prospective study

Background

Blood volume (BV) is a critical factor for physical endurance in chronic stroke patients, while hypervolemia can worsen hypertension in these patients. This prospective study assessed whether rehabilitation combined with protein supplementation immediately after each exercise for 3 weeks would improve plasma volume (PV) and BV as well as physical endurance without worsening hypertension.

Methods

Ambulatory patients with chronic cerebrovascular disease who received a 3-week rehabilitation program with high protein jelly (intervention group [PG]; n = 8; 10-g protein) or protein-free jelly (control group [CG]; n = 8) consumed within 30 min after each exercise. PV and BV were assessed while measuring the 6-min walking distance (6MWD), peak oxygen consumption (VO_2peak), strength of knee extension, and resting blood pressure before and after the intervention. Two-way ANOVA was used to determine whether there was an interaction of time × group. The difference between before and after intervention or between the groups by post-hoc test (Tukey’s test) at the level of P < 0.05.

Results

The 6MWD increased only in the PG (P = 0.001; an interaction of Group and Time, P = 0.037). PV and BV increased only in the PG (P < 0.05). VO_2peak and strength of knee extension in the paralysed limb increased in both groups (P < 0.05). The resting blood pressure did not worsen after the intervention.

Conclusions

In chronic post-stroke patients, 3-week rehabilitation combined with protein intake immediately after exercise increased 6MWD simultaneously with increased PV and BV, but it did not increase resting blood pressure. The present regimen is acceptable and effective for ambulatory patients with chronic cerebrovascular disease.

Name of the registry Examining effects of protein supplementation on functional improvement during rehabilitation intervention in chronic stroke patients

Trial registration number UMIN000028009; date of registration: 30/06/2017. This study was registered prospectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-022-00429-x.

Extreme Heat and Cardiovascular Health: What a Cardiovascular Health Professional Should Know

As global temperatures continue to rise, extreme heat events are becoming more frequent and intense. Extreme heat affects cardiovascular health as it is associated with a greater risk of adverse cardiovascular events, especially for adults with preexisting cardiovascular diseases. Nonetheless, the pathophysiology underlying the association between extreme heat and cardiovascular risk remains understudied. Furthermore, specific recommendations to mitigate the effects of extreme heat on cardiovascular health remain limited to guide clinical practice within the context of a warming climate. The overall objective of this review article is to raise awareness that extreme heat poses a risk for cardiovascular health. Specifically, the review discusses why cardiovascular healthcare professionals should care about extreme heat, how extreme heat affects cardiovascular health, and recommendations to minimise the cardiovascular consequences of extreme heat. Future research directions are also provided to further our understating of the cardiovascular health consequences of extreme heat. A better awareness and understanding of the cardiovascular consequences of extreme heat will help cardiovascular health professionals assess the risk and optimise the care of their patients exposed to an increasingly warm climate.

Mortality attributable to heat and cold among the elderly in Sofia, Bulgaria

Although a number of epidemiological studies have examined the effects of non-optimal temperatures on mortality in Europe, evidence about the mortality risks associated with exposures to hot and cold temperatures in Bulgaria is scarce. This study provides evidence about mortality attributable to non-optimal temperatures in adults aged 65 and over in Sofia, Bulgaria, between 2000 and 2017. We quantified the relationship between the daily mean temperature and mortality in the total elderly adult population aged 65 and over, among males and females aged 65 and over, as well as individuals aged 65-84 and 85 years or older. We used a distributed lag non-linear model with a 25-day lag to fully capture the effects of both cold and hot temperatures and calculated the fractions of mortality attributable to mild and extreme hot and cold temperatures. Cold temperatures had a greater impact on mortality than hot temperatures during the studied period. Most of the temperature-attributable mortality was due to moderate cold, followed by moderate heat, extreme cold, and extreme heat. The total mortality attributable to non-optimal temperatures was greater among females compared to males and among individuals aged 85 and over compared to those aged 65 to 84. The findings of this study can serve as a foundation for future research and policy development aimed at characterizing and reducing the risks from temperature exposures among vulnerable populations in the country, climate adaptation planning and improved public health preparedness, and response to non-optimal temperatures.

Temperature regulation during exercise in the heat: Insights for the aging athlete

OBJECTIVE

The purpose of this review is to evaluate the currently-available literature regarding the impact of both primary aging and age-related fitness on thermoregulatory function during exercise in the heat. In so doing, we aim to (1) characterize the influence of fitness in mitigating age-related declines in thermoregulation, (2) address the limitations of prior experimental approaches for investigating age-related thermoregulatory impairments, (3) examine to what extent aerobic fitness can be maintained in the aging athlete, and (4) begin to address the specific environmental conditions in which age-related impairments in thermoregulatory function may place highly active older adults at increased risk for heat-related illness and injury and/or limited performance.

DESIGN

Mini-review.

METHODS

Review and synthesis of available information.

RESULTS

The earth's climate is warming, accompanied by a consequently greater frequency and severity of extreme heat events. At the same time, lifespan is increasing and people of all ages are staying increasingly active. Age-related impairments in thermoregulatory function are well-documented, leading to increased heat-related health risks and reduced exercise/athletic performance for older adults in hot environmental conditions. High aerobic fitness improves body temperature regulation during exercise via augmented sweating and improved cardiovascular function, including cardiac output and skin blood flow, in humans of all ages.

CONCLUSIONS

The masters athlete is better suited for exercise/heat-stress compared to his or her less fit peers. However, while age and thermoregulation in general has been studied extensively, research on the most fit older adults, including highly competitive athletes, is generally lacking.

Internet of Things (IoT) System and Field Sensors for Exercise Intensity Measurements

Although exercise training according to individual peak aerobic capacity ( V ˙ o_2peak ) has been recommended at all ages, sensors available in the field are limited. The most popular sensors in the field are pedometers, but they cannot be used to monitor exercise intensity. Instead, although heart rate (HR) monitors are broadly available in the field to estimate exercise intensity, HR responses to exercise vary by individual according to physical fitness and environmental conditions, which hinders the precise measurement of energy expenditure. These issues make it difficult for exercise physiologists to collaborate with geneticists, nutritionists, and clinicians using the internet of things (IoT). To conquer these problems, we have developed a device that is equipped with a triaxial accelerometer and a barometer to measure energy expenditure during interval walking training (IWT) in the field with inclines. IWT is a training regimen to repeat fast and slow walking for 3 min each, equivalent to greater than 70% and approximately 40% of individual V ˙ o_2peak , respectively. Additionally, we developed an IoT system that enables users to receive instructions from trainers according to their walking records even if they live far away. Since the system is available at low cost with minimum personnel, we can investigate any factors affecting the adherence to and effects of IWT in a large population for a long period. This system was also used to verify any effects of nutritional supplements during IWT and to examine the value of applying IWT to clinical medicine. © 2020 American Physiological Society. Compr Physiol 10:1207-1240, 2020.

The effect of lifelong endurance exercise on cardiovascular structure and exercise function in women

KEY POINTS

The beneficial effects of sustained or lifelong (>25 years) endurance exercise on cardiovascular structure and exercise function have been largely established in men. The current findings indicate that committed (≥4 weekly exercise sessions) lifelong exercise results in substantial benefits in exercise capacity ( V ̇ O 2 max ), cardiovascular function at submaximal and maximal exercise, left ventricular mass and compliance, and blood volume compared to similarly aged or even younger (middle-age) untrained women. Endurance exercise training should be considered a key strategy to prevent cardiovascular disease with ageing in women as well as men.

ABSTRACT

This study was a retrospective, cross-sectional analysis of exercise performance and left ventricular (LV) morphology in 70 women to examine whether women who have performed regular, lifelong endurance exercise acquire the same beneficial adaptations in cardiovascular structure and function and exercise performance that have been reported previously in men. Three groups of women were examined: (1) 35 older (>60 years) untrained women (older untrained, OU), (2) 13 older women who had consistently performed four or more endurance exercise sessions weekly for at least 25 years (older trained, OT), and (3) 22 middle-aged (range 35-59 years) untrained women (middle-aged untrained, MU) as a reference control for the appropriate age-related changes. Oxygen uptake ( V ̇ O 2 ) and cardiovascular function (cardiac output ( Q ̇ ); stroke volume (SV) acetylene rebreathing) were examined at rest, steady-state submaximal exercise and maximal exercise (maximal oxygen uptake, V ̇ O 2 max ). Blood volume (CO rebreathing) and LV mass (cardiac magnetic resonance imaging), plus invasive measures of static and dynamic chamber compliance were also examined. V ̇ O 2 max (p < 0.001) and maximal exercise Q ̇ and SV were larger in older trained women compared to the two untrained groups (∼17% and ∼27% for Q ̇ and SV, respectively, versus MU; ∼40% and ∼38% versus OU, all p < 0.001). Blood volume (mL kg^-1 ) and LV mass index (g m^-2 ) were larger in OT versus OU (∼11% and ∼16%, respectively, both P ≤ 0.015) Static LV chamber compliance was greater in OT compared to both untrained groups (median (25-75%): MU: 0.065 (0.049-0.080); OU: 0.085 (0.061-0.138); OT: 0.047 (0.031-0.054), P ≤ 0.053). Collectively, these findings indicate that lifetime endurance exercise appears to be extremely effective at preserving or even enhancing cardiovascular structure and function with advanced age in women.

Thermoregulation in the Aging Population and Practical Strategies to Overcome a Warmer Tomorrow

As global temperatures continue to rise, improving thermal tolerance in the aged population is crucial to counteract age-associated impairments in thermoregulatory function. Impairments in reflex cutaneous vasodilation and sweating response can augment the vulnerability of older adults to heat-related injuries following exposure to heat stress. Mechanisms underlying a compromised cutaneous vasodilation are suggested to include reduced sympathetic neural drive, diminished cholinergic co-transmitter contribution, and altered second messenger signaling events. On the other hand, impairments in sweating response are ascribed to reduced sweat gland cholinergic sensitivity and altered cyclooxygenase and nitric oxide signaling. Several practical mitigation strategies such as exercise, passive heating, and behavioral adaptations are proposed as means to overcome heat stress and improve thermal tolerance in the aged. Aerobic exercise training is shown to be amongst the most effective ways to enhance thermoregulatory function. However, in elderly with limited exercise capability due to chronic diseases and mobility issues, passive heating can serve as a functional alternative as it has been shown to confer similar benefits to that of exercise training. Supplementary to exercise training and passive heating, behavioral adaptations can be applied to further enhance the heat-preparedness of the aged.

The Dynamic and Correlation of Skin Temperature and Cardiorespiratory Fitness in Male Endurance Runners

During endurance exercise, skin temperature (Tsk) plays a fundamental role in thermoregulatory processes. Environmental temperature is the biggest determinant of the Tsk. During exercise, the response of the skin temperature might be influenced by aerobic fitness (VO_2peak). The aim of this study was to analyze and compare the dynamic of Tsk in high (HF) and moderately (MF) fit endurance runners during a progressive maximal stress test. Seventy-nine male endurance runners were classified into HF (n = 35; VO_2peak = 56.62 ± 4.31 mL/kg/min) and MF (n = 44; VO_2peak = 47.86 ± 5.29 mL/kg/min) groups. Tsk and cardiovascular data were continuously monitored during an incremental exercise, followed by a recovery period of five minutes. Results revealed that the MF group exhibited lower VO_2peak, Speed_peak, ventilation (VE), muscle mass %, and higher BMI and fat mass % than the HF group (all p < 0.001). HF had significantly higher Tsk at baseline, and at 60% and 70% of peak workload (all p < 0.05). Tsk_peak correlated with age, fat mass %, muscle mass %, VO_2peak, Speed_peak, HR and VE (all p < 0.05). These findings indicate that VO_2peak was positively associated with increased Tsk during incremental exercise in male endurance runners.

Interactions between body fluid homeostasis and thermoregulation in humans

Humans are unique in their ability to control body temperature with a large amount of skin blood flow and sweat rate while exercising in an upright position. However, cutaneous vasodilation in the body reduces total peripheral resistance and blood pooling in cutaneous veins decreases venous return to the heart and cardiac filling pressure. In addition, hypovolemia by sweating accelerates the reduction in cardiac filling pressure. These may threaten the maintenance of blood pressure if they are not compensated for. To prevent this, cutaneous vasodilation and sweat rate are suppressed by baroreflexes or hyperosmolality with dehydration. These mechanisms suppress heat dissipation, accelerate the increase in body temperature, and sometimes cause heat stroke. As a countermeasure to prevent this, we have recommended glucose electrolyte solutions but recently found that aerobic training with carbohydrate + whey protein supplementation markedly improves heat dissipation mechanisms by plasma volume expansion. In this article, we will discuss the importance of improving body fluid homeostasis for thermoregulation under heat stress in humans and the strategy to attain this.

The effects of aerobic exercise on eGFR, blood pressure and VO2peak in patients with chronic kidney disease stages 3-4: A systematic review and meta-analysis

BACKGROUND

CKD is associated with several comorbidities, cardiovascular disease being the most significant. Aerobic training has a beneficial effect on cardiovascular health in healthy and some well-defined non-healthy populations. However, the effect of aerobic training on glomerular filtration rate in patients with CKD stages 3-4 is unclear.

OBJECTIVE

To review the effects of aerobic exercise training on kidney and cardiovascular function in patients with chronic kidney disease (CKD) stages 3-4.

METHODS

A random-effects meta-analysis was performed to analyse published randomized controlled trials through February 2018 on the effect of aerobic training on estimated glomerular filtration rate, blood pressure and exercise tolerance in patients with CKD stages 3-4. Web of Science, PubMed and Embase databases were searched for eligible studies.

RESULTS

11 randomized controlled trials were selected including 362 participants in total. Favourable effects were observed on estimated glomerular filtration rate (+2.16 ml/min per 1.73m2; [0.18; 4.13]) and exercise tolerance (+2.39 ml/kg/min; [0.99; 3.79]) following an on average 35-week aerobic training program when compared to standard care. No difference in change in blood pressure was found.

CONCLUSIONS

There is a small beneficial effect of aerobic training on estimated glomerular filtration rate and exercise tolerance, but not on blood pressure, in patients with CKD stages 3-4. However, data are limited and pooled findings were rated as of low to moderate quality.

Aging and Thermoregulatory Control: The Clinical Implications of Exercising under Heat Stress in Older Individuals

Climate change is predicted to bring about a greater variability in weather patterns with an increase in extreme weather events such as sustained heat waves. This change may have a direct impact on population health since heat waves can exceed the physiological limit of compensability of vulnerable individuals. Indeed, many clinical reports suggest that individuals over the age of 60 years are consistently the most vulnerable, experiencing significantly greater adverse heat-related health outcomes than any other age cohort during environmental heat exposure. There is now evidence that aging is associated with an attenuated physiological ability to dissipate heat and that the risk of heat-related illness in these individuals is elevated, particularly when performing physical activity in the heat. The purpose of this review is to discuss mechanisms of thermoregulatory control and the factors that may increase the risk of heat-related illness in older individuals. An understanding of the mechanisms responsible for impaired thermoregulation in this population is of particular importance, given the current and projected increase in frequency and intensity of heat waves, as well as the promotion of regular exercise as a means of improving health-related quality of life and morbidity and mortality. As such, the clinical implications of this work in this population will be discussed.

Interval Walking Training and Nutritional Intake to Increase Plasma Volume in Elderly

PURPOSE

Aerobic training-induced plasma volume (PV) expansion improves thermoregulation, and carbohydrate (CHO) + whey protein supplementation enhanced the effects in older people; however, these were suggested by studies on gym-based cycling training but not on home-based interval walking training (IWT). Moreover, long-term walking training effects on PV remain unknown.

METHODS

Seventeen male and 10 female subjects (~69 yr), having performed IWT for ≥24 months before the study, were used. After pre-intervention measurement (PRE) of PV, plasma albumin content (Albcont), fasting glucose concentration ([Glc]f), and HbA1c, the subjects were randomly divided into two groups: CHO and Pro-CHO, either consuming CHO (22.5 g) alone or CHO (15 g) + whey protein (10 g), respectively, during additional 5-month IWT from May to November, 2009. After the additional IWT, we measured the same variables again (postintervention measurement).

RESULTS

The baseline PV and Albcont were significantly correlated with the number of IWT days for the 12 months preceding PRE (r = 0.716, P < 0.001 and r = 0.671, P < 0.001, respectively). In postintervention, PV and Albcont marginally decreased in CHO from the baselines (P = 0.081 and P = 0.130, respectively) with increased HbA1c (P < 0.001) after correction for the baseline [Glc]f by ANCOVA, but these values remained unchanged in Pro-CHO (both, P > 0.74), with significant differences in the changes between groups (P = 0.020, P = 0.041, and P = 0.018 respectively).

CONCLUSIONS

PV was proportional to the number of IWT days for 12 months and a CHO + whey protein supplementation during the 5-month IWT prevented PV reduction for the period of no supplementation, which might be partially linked with blood glucose control mechanisms.

Erythropoiesis with endurance training: dynamics and mechanisms

The purpose of the present study was to characterize the progression of red blood cell volume (RBCV) expansion and potential volumetric and endocrine regulators of erythropoiesis during endurance training (ET). Nine healthy, untrained volunteers (age = 27 ± 4 yr) underwent supervised ET consisting of 3–4 × 60 min cycle ergometry sessions per week for 8 wk. Plasma volume (PV), RBCV, and overnight fasting hematological markers were determined before and at weeks 2, 4, and 8 of ET. In addition, plasma erythropoietin (EPO), cortisol, copeptin, and proatrial natriuretic peptide concentrations were measured during a 3-h morning period at baseline and postexercise at weeks 1 and 8. PV increased from baseline (2,405 ± 335 ml) at weeks 2, 4, and 8 (+374 ± 194, +505 ± 156, and +341 ± 160 ml, respectively, P < 0.001). Increases in RBCV from baseline (1,737 ± 442 ml) were manifested at week 4 (+109 ± 114 ml, P = 0.030) and week 8 (+205 ± 109 ml, P = 0.001). Overnight fasting plasma EPO concentration increased from baseline (11.3 ± 4.8 mIU/ml) at week 2 (+2.5 ± 2.8 mIU·ml−1, P = 0.027) and returned to baseline concentration at weeks 4 and 8. Higher 3-h-postexercise EPO concentration was observed at week 1 (11.6 mIU/ml) compared with week 8 (8.4 ± 3.9 mIU/ml, P = 0.009) and baseline (9.0 ± 4.2 mIU/ml, P = 0.019). Linear relationships between EPO concentration and hematocrit (β = −56.2, P < 0.001) and cortisol (β = 0.037, P < 0.001) were detected throughout the ET intervention. In conclusion, ET leads to mild, transient increases in circulating EPO concentration, concurring with early PV expansion and lowered hematocrit, preceding gradual RBCV enhancement.

Altered thermoregulatory responses in heart failure patients exercising in the heat

Heart failure (HF) patients appear to exhibit impaired thermoregulatory capacity during passive heating, as evidenced by diminished vascular conductance. Although some preliminary studies have described the thermoregulatory response to passive heating in HF, responses during exercise in the heat remain to be described. Therefore, the aim of this study was to compare thermoregulatory responses in HF and controls (CON) during exercise in the heat. Ten HF (NYHA classes I-II) and eight CON were included. Core temperature (Tc), skin temperature (Tsk), and cutaneous vascular conductance (CVC) were assessed at rest and during 1 h of exercise at 60% of maximal oxygen uptake. Metabolic heat production (Hprod) and the evaporative requirements for heat balance (Ereq) were also calculated. Whole-body sweat rate was determined from pre-post nude body mass corrected for fluid intake. While Hprod (HF: 3.9 ± 0.9; CON: 6.4 ± 1.5 W/kg) and Ereq (HF: 3.3 ± 0.9; CON: 5.6 ± 1.4 W/kg) were lower (P < 0.01) for HF compared to CON, both groups demonstrated a similar rise in Tc (HF: 0.9 ± 0.4; CON: 1.0 ± 0.3°C). Despite this similar rise in Tc, Tsk (HF: 1.6 ± 0.7; CON: 2.7 ± 1.2°C), and the elevation in CVC (HF: 1.4 ± 1.0; CON: 3.0 ± 1.2 au/mmHg) was lower (P < 0.05) in HF compared to CON Additionally, whole-body sweat rate (HF: 0.36 ± 0.15; CON: 0.81 ± 0.39 L/h) was lower (P = 0.02) in HF compared to CON Patients with HF appear to be limited in their ability to manage a thermal load and distribute heat content to the body surface (i.e., skin), secondary to impaired circulation to the periphery.

The effect of 1 year of Alagebrium and moderate-intensity exercise training on left ventricular function during exercise in seniors: a randomized controlled trial

Sedentary aging leads to left ventricular (LV) and vascular stiffening due in part to advanced glycation end-products (AGEs) cross-linking of extracellular matrix proteins. Vigorous lifelong exercise ameliorates age-related cardiovascular (CV) stiffening and enhances exercise LV function, although this effect is limited when exercise is initiated later in life. We hypothesized that exercise training might be more effective at improving the impact of age-related CV stiffening during exercise when combined with an AGE cross-link breaker (Alagebrium). Sixty-two seniors (≥60 yr) were randomized into four groups: sedentary + placebo, sedentary + Alagebrium, exercise + placebo, and exercise + Alagebrium for 1 yr. Moderate-intensity aerobic exercise was performed 3-4 sessions/wk; controls underwent similar frequency of yoga/balance training. Twenty-four similarly-aged, lifelong exercisers (4-5 sessions/wk) served as a comparator for the effect of lifelong exercise on exercising LV function. Oxygen uptake (Douglas bags), stroke index (SI; acetylene rebreathing), and effective arterial elastance (Ea) were collected at rest and submaximal and maximal exercise. Maximum O2 uptake (23 ± 5 to 25 ± 6 ml·kg(-1)·min(-1)) increased, while SI (35 ± 11 to 39 ± 12 ml/m(2)) and Ea (4.0 ± 1.1 to 3.7 ± 1.2 mmHg·ml(-1)·m(-2)) were improved across all conditions with exercise, but remained unchanged in controls (exercise × time, P ≤ 0.018). SI or Ea were not affected by Alagebrium (medication × time, P ≥ 0.468) or its combination with exercise (interaction P ≥ 0.252). After 1 yr of exercise plus Alagebrium, exercise SI and Ea remained substantially below that of lifelong exercisers (15-24 and 9-22%, respectively, P ≤ 0.415). In conclusion, Alagebrium plus exercise had no synergistic effect on exercise LV function and failed to achieve levels associated with lifelong exercise, despite a similar exercise frequency.

Effects of hypervolemia by protein and glucose supplementation during aerobic training on thermal and arterial pressure regulations in hypertensive older men

In Japan, the incidence of heat illness in older people has rapidly increased during midsummer in the last decade, and we suggested that whey-protein+carbohydrate supplementation during aerobic training would increased plasma volume (PV) to enhance thermoregulatory adaptation in older men (J Appl Physiol 107: 725-733, 2009); however, >60% of people age 65 and older suffer from hypertension, and the symptoms may be worsened by hypervolemia. To examine this, we randomly divided 21 older men (∼69 yr) with ∼160 mmHg for systolic and ∼90 mmHg for diastolic blood pressure at rest into two groups: Glc (n = 11) consuming glucose alone (25 g) and Pro-Glc (n = 10) consuming whey protein (10 g) + glucose (15 g), immediately after cycling exercise at 60-75% of peak aerobic capacity (V̇o_{2 peak}) for 60 min/day, 3 days/wk, for 8 wk. Before and after training, we measured PV (dye dilution), baroreflex sensitivity (BRS) of heart rate (Valsalva maneuver), and carotid arterial compliance (CAC) from carotid arterial diameter (ultrasound imaging) responses to pulsatile arterial pressure change (photoplethysmography) at rest. Additionally, we measured esophageal temperature (T_es) and forearm skin blood flow (plethysmography) during exercise at 60% pretraining V̇o_{2 peak} for 20 min in a warm environment. We found that the forearm skin vascular conductance response to increased T_es was enhanced in Pro-Glc with increased PV, but this was not found in Glc; however, despite the increased PV, arterial blood pressures rather decreased with increased CAC and BRS in Pro-Glc. Thus, the prescription was applicable to older men with hypertension to prevent heat illness during exercise.

Characteristics of hyperthermia-induced hyperventilation in humans

In humans, hyperthermia leads to activation of a set of thermoregulatory responses that includes cutaneous vasodilation and sweating. Hyperthermia also increases ventilation in humans, as is observed in panting dogs, but the physiological significance and characteristics of the hyperventilatory response in humans remain unclear. The relative contribution of respiratory heat loss to total heat loss in a hot environment in humans is small, and this hyperventilation causes a concomitant reduction in arterial CO₂ pressure (hypocapnia), which can cause cerebral hypoperfusion. Consequently, hyperventilation in humans may not contribute to the maintenance of physiological homeostasis (i.e., thermoregulation). To gain some insight into the physiological significance of hyperthermia-induced hyperventilation in humans, in this review, we discuss 1) the mechanisms underlying hyperthermia-induced hyperventilation, 2) the factors modulating this response, and 3) the physiological consequences of the response.

iNOS-dependent sweating and eNOS-dependent cutaneous vasodilation are evident in younger adults, but are diminished in older adults exercising in the heat

Nitric oxide synthase (NOS) contributes to sweating and cutaneous vasodilation during exercise in younger adults. We hypothesized that endothelial NOS (eNOS) and neuronal NOS (nNOS) mediate NOS-dependent sweating, whereas eNOS induces NOS-dependent cutaneous vasodilation in younger adults exercising in the heat. Further, aging may upregulate inducible NOS (iNOS), which may attenuate sweating and cutaneous vasodilator responses. We hypothesized that iNOS inhibition would augment sweating and cutaneous vasodilation in exercising older adults. Physically active younger (n = 12, 23 ± 4 yr) and older (n = 12, 60 ± 6 yr) adults performed two 30-min bouts of cycling at a fixed rate of metabolic heat production (400 W) in the heat (35°C). Sweat rate and cutaneous vascular conductance (CVC) were evaluated at four intradermal microdialysis sites with: 1) lactated Ringer (control), 2) nNOS inhibitor (nNOS-I, NPLA), 3) iNOS inhibitor (iNOS-I, 1400W), or 4) eNOS inhibitor (eNOS-I, LNAA). In younger adults during both exercise bouts, all inhibitors decreased sweating relative to control, albeit a lower sweat rate was observed at iNOS-I compared with eNOS-I and nNOS-I sites (all P < 0.05). CVC at the eNOS-I site was lower than control in younger adults throughout the intermittent exercise protocol (all P < 0.05). In older adults, there were no differences between control and iNOS-I sites for sweating and CVC during both exercise bouts (all P > 0.05). We show that iNOS and eNOS are the main contributors to NOS-dependent sweating and cutaneous vasodilation, respectively, in physically active younger adults exercising in the heat, and that iNOS inhibition does not alter sweating or cutaneous vasodilation in exercising physically active older adults.

Optimal composition of fluid-replacement beverages

The objective of this article is to provide a review of the fundamental aspects of body fluid balance and the physiological consequences of water imbalances, as well as discuss considerations for the optimal composition of a fluid replacement beverage across a broad range of applications. Early pioneering research involving fluid replacement in persons suffering from diarrheal disease and in military, occupational, and athlete populations incurring exercise- and/or heat-induced sweat losses has provided much of the insight regarding basic principles on beverage palatability, voluntary fluid intake, fluid absorption, and fluid retention. We review this work and also discuss more recent advances in the understanding of fluid replacement as it applies to various populations (military, athletes, occupational, men, women, children, and older adults) and situations (pathophysiological factors, spaceflight, bed rest, long plane flights, heat stress, altitude/cold exposure, and recreational exercise). We discuss how beverage carbohydrate and electrolytes impact fluid replacement. We also discuss nutrients and compounds that are often included in fluid-replacement beverages to augment physiological functions unrelated to hydration, such as the provision of energy. The optimal composition of a fluid-replacement beverage depends upon the source of the fluid loss, whether from sweat, urine, respiration, or diarrhea/vomiting. It is also apparent that the optimal fluid-replacement beverage is one that is customized according to specific physiological needs, environmental conditions, desired benefits, and individual characteristics and taste preferences.

Strength and endurance training prescription in healthy and frail elderly

Aging is associated with declines in the neuromuscular and cardiovascular systems, resulting in an impaired capacity to perform daily activities. Frailty is an age-associated biological syndrome characterized by decreases in the biological functional reserve and resistance to stressors due to changes in several physiological systems, which puts older individuals at special risk of disability. To counteract the neuromuscular and cardiovascular declines associated with aging, as well as to prevent and treat the frailty syndrome, the strength and endurance training seems to be an effective strategy to improve muscle hypertrophy, strength and power output, as well as endurance performance. The first purpose of this review was discuss the neuromuscular adaptations to strength training, as well as the cardiovascular adaptations to endurance training in healthy and frail elderly subjects. In addition, the second purpose of this study was investigate the concurrent training adaptations in the elderly. Based on the results found, the combination of strength and endurance training (i.e., concurrent training) performed at moderate volume and moderate to high intensity in elderly populations is the most effective way to improve both neuromuscular and cardiorespiratory functions. Moreover, exercise interventions that include muscle power training should be prescribed to frail elderly in order to improve the overall physical status of this population and prevent disability.

Strength and endurance training prescription in healthy and frail elderly

Aging is associated with declines in the neuromuscular and cardiovascular systems, resulting in an impaired capacity to perform daily activities. Frailty is an age-associated biological syndrome characterized by decreases in the biological functional reserve and resistance to stressors due to changes in several physiological systems, which puts older individuals at special risk of disability. To counteract the neuromuscular and cardiovascular declines associated with aging, as well as to prevent and treat the frailty syndrome, the strength and endurance training seems to be an effective strategy to improve muscle hypertrophy, strength and power output, as well as endurance performance. The first purpose of this review was discuss the neuromuscular adaptations to strength training, as well as the cardiovascular adaptations to endurance training in healthy and frail elderly subjects. In addition, the second purpose of this study was investigate the concurrent training adaptations in the elderly. Based on the results found, the combination of strength and endurance training (i.e., concurrent training) performed at moderate volume and moderate to high intensity in elderly populations is the most effective way to improve both neuromuscular and cardiorespiratory functions. Moreover, exercise interventions that include muscle power training should be prescribed to frail elderly in order to improve the overall physical status of this population and prevent disability.

Effect of a single finnish sauna session on white blood cell profile and cortisol levels in athletes and non-athletes

The aim of the present study was to investigate the effect of Finnish sauna bathing on a white blood cell profile, cortisol levels and selected physiological indices in athletes and non-athletes. The study evaluated 9 trained middle-distance runners and 9 male non-athletes. The subjects from both groups participated in 15-minute sauna sessions until their core temperature rose by 1.2°C (mean temperature in the sauna room was 96° ± 2°C; relative humidity was 15 ± 3%) with a 2 minute cool down with water at a temperature of 19–20°C. Body mass was measured before and after the session and blood samples were taken for tests. Rectal temperature was monitored at five-minute intervals during the whole session. Serum total protein, haematological indices and cortisol levels were determined. Sauna bathing caused higher body mass loss and plasma volume in the athletes compared to the group of non-athletes. After the sauna session, an increased number of white blood cells, lymphocyte, neutrophil and basophil counts was reported in the white blood cell profile. Higher increments in leukocyte and monocyte after the sauna bathing session were recorded in the group of athletes compared to untrained subjects. The obtained results indicated that sauna bathing stimulated the immune system to a higher degree in the group of athletes compared to the untrained subjects.

The evaporative requirement for heat balance determines whole-body sweat rate during exercise under conditions permitting full evaporation

Although the requirements for heat dissipation during exercise are determined by the necessity for heat balance, few studies have considered them when examining sweat production and its potential modulators. Rather, the majority of studies have used an experimental protocol based on a fixed percentage of maximum oxygen uptake (% ). Using multiple regression analysis, we examined the independent contribution of the evaporative requirement for heat balance (Ereq) and % to whole-body sweat rate (WBSR) during exercise. We hypothesised that WBSR would be determined by Ereq and not by % . A total of 23 males performed two separate experiments during which they exercised for 90 min at different rates of metabolic heat production (200, 350, 500 W) at a fixed air temperature (30°C, n = 8), or at a fixed rate of metabolic heat production (290 W) at different air temperatures (30, 35, 40°C, n = 15 and 45°C, n = 7). Whole-body evaporative heat loss was measured by direct calorimetry and used to calculate absolute WBSR in grams per minute. The conditions employed resulted in a wide range of Ereq (131-487 W) and % (15-55%). The individual variation in non-steady-state (0-30 min) and steady-state (30-90 min) WBSR correlated significantly with Ereq (P < 0.001). In contrast, % correlated negatively with the residual variation in WBSR not explained by Ereq, and marginally increased (∼2%) the amount of total variability in WBSR described by Ereq alone (non-steady state: R(2) = 0.885; steady state: R(2) = 0.930). These data provide clear evidence that absolute WBSR during exercise is determined by Ereq, not by % . Future studies should therefore use an experimental protocol which ensures a fixed Ereq when examining absolute WBSR between individuals, irrespective of potential differences in relative exercise intensity.

Effects of macronutrient intake on thigh muscle mass during home-based walking training in middle-aged and older women

We examined whether post-exercise macronutrient supplementation during a 5-month home-based interval walking training (IWT) accelerated exercise-induced increases in skeletal muscle mass and strength in healthy middle-aged and older women. Thirty-five women (41-78 years) were randomly divided into two groups: IWT alone (CNT, n = 18) or IWT plus post-exercise macronutrient (7.6 g protein, 32.5 g carbohydrate, and 4.4 g fat) supplementation (NUT, n = 17). For IWT, all subjects were instructed to repeat five or more sets of 3-min low-intensity walking at 40% peak aerobic capacity (Vo2 peak ), followed by a 3-min high-intensity walking above 70% Vo2 peak per day for 4 or more days per week. We determined Vo2 peak , thigh muscle tissue area by computer tomography, and thigh muscle strength in all subjects before and after IWT. We found that an increase in hamstring muscle tissue area was 2.8 ± 1.2% in NUT vs -1.0 ± 0.7% in CNT and that in isometric knee flexion force was 16.3 ± 3.7% in NUT vs 6.5 ± 3.0% in CNT; both were significantly higher in NUT than in CNT (both, P < 0.001). Thus, post-exercise macronutrient supplementation enhanced the increases in thigh muscle mass and strength, although partially, in home-based IWT in middle-aged and older women.

Resistance training induced increase in VO2max in young and older subjects

It is an undeniable fact that resistance training (RT) is a potent stimulus for muscle hypertrophy and strength gain, but it is less understood whether RT can increase maximal aerobic capacity (VO2max). The purpose of this brief review is to discuss whether or not RT enhances VO2max in young (20–40 years) and older subjects (>60 years). Only 3 of 17 studies involving young subjects have indicated significant increases in VO2max following RT, while six of nine studies in older subjects have reported significant improvements in VO2max following RT. There was a significant negative correlation between the initial VO2max and RT-induced change in VO2max. This result suggests that RT-induced increase in VO2max is dependent upon the subject’s initial VO2max. The RT-induced increase in VO2max may be elicited when their initial relative VO2max is lower than 25 ml/kg/min for older subjects and lower than 40 ml/kg/min for young subjects. Thus, RT can be expected to improve concurrently both muscular and cardiovascular fitnesses within a single mode of RT when young and old persons have initially low fitness levels.

Development of an Exercise Meter using Triaxial Acceleration Data

Shinshu University and an NPO "JTRC" (Jukunen Taiiku Daigaku Research Center; a health promotion and support organization) provide exercise guidance focused on walking activity with the object of enhancing strength among elderly individuals. Sanyo Electric has developed an exercise meter as a tool to promote these efforts effectively. This exercise meter is equipped with a function providing estimates of energy consumption, leg muscle strength, and endurance based on triaxial acceleration data from the lumbar region. In this paper, we provide an outline of the estimation techniques and present an application of this exercise meter.

Large differences in peak oxygen uptake do not independently alter changes in core temperature and sweating during exercise

The independent influence of peak oxygen uptake (Vo(₂ peak)) on changes in thermoregulatory responses during exercise in a neutral climate has not been previously isolated because of complex interactions between Vo(₂ peak), metabolic heat production (H(prod)), body mass, and body surface area (BSA). It was hypothesized that Vo(₂ peak) does not independently alter changes in core temperature and sweating during exercise. Fourteen males, 7 high (HI) Vo(₂ peak): 60.1 ± 4.5 ml·kg⁻¹·min⁻¹; 7 low (LO) Vo(₂ peak): 40.3 ± 2.9 ml·kg⁻¹·min⁻¹ matched for body mass (HI: 78.2 ± 6.1 kg; LO: 78.7 ± 7.1 kg) and BSA (HI: 1.97 ± 0.08 m²; LO: 1.94 ± 0.08 m²), cycled for 60-min at 1) a fixed heat production (FHP trial) and 2) a relative exercise intensity of 60% Vo(₂ peak) (REL trial) at 24.8 ± 0.6°C, 26 ± 10% RH. In the FHP trial, H(prod) was similar between the HI (542 ± 38 W, 7.0 ± 0.6 W/kg or 275 ± 25 W/m²) and LO (535 ± 39 W, 6.9 ± 0.9 W/kg or 277 ± 29 W/m²) groups, while changes in rectal (T(re): HI: 0.87 ± 0.15°C, LO: 0.87 ± 0.18°C, P = 1.00) and aural canal (T(au): HI: 0.70 ± 0.12°C, LO: 0.74 ± 0.21°C, P = 0.65) temperature, whole-body sweat loss (WBSL) (HI: 434 ± 80 ml, LO: 440 ± 41 ml; P = 0.86), and steady-state local sweating (LSR(back)) (P = 0.40) were all similar despite relative exercise intensity being different (HI: 39.7 ± 4.2%, LO: 57.6 ± 8.0% Vo(2 peak); P = 0.001). At 60% Vo(2 peak), H(prod) was greater in the HI (834 ± 77 W, 10.7 ± 1.3 W/kg or 423 ± 44 W/m²) compared with LO (600 ± 90 W, 7.7 ± 1.4 W/kg or 310 ± 50 W/m²) group (all P < 0.001), as were changes in T(re) (HI: 1.43 ± 0.28°C, LO: 0.89 ± 0.19°C; P = 0.001) and T(au) (HI: 1.11 ± 0.21°C, LO: 0.66 ± 0.14°C; P < 0.001), and WBSL between 0 and 15, 15 and 30, 30 and 45, and 45 and 60 min (all P < 0.01), and LSR(back) (P = 0.02). The absolute esophageal temperature (T(es)) onset for sudomotor activity was ∼0.3°C lower (P < 0.05) in the HI group, but the change in T(es) from preexercise values before sweating onset was similar between groups. Sudomotor thermosensitivity during exercise were similar in both FHP (P = 0.22) and REL (P = 0.77) trials. In conclusion, changes in core temperature and sweating during exercise in a neutral climate are determined by H(prod), mass, and BSA, not Vo(₂ peak).

Protein and carbohydrate supplementation during 5-day aerobic training enhanced plasma volume expansion and thermoregulatory adaptation in young men

We examined whether protein and carbohydrate (CHO) supplementation during 5-day training enhanced plasma volume (PV) expansion and thermoregulatory and cardiovascular adaptations in young men. Eighteen men [age 23 ± 4 (SD) yr] were divided into two groups according to supplements: placebo (CNT: 0.93 kcal/kg, 0.00 g protein/kg, n = 9) and protein and CHO (Pro-CHO: 3.6 kcal/kg, 0.36 protein/kg, n = 9). Subjects in both groups performed a cycling exercise at 70% peak oxygen consumption rate (VO2peak), 30 min/day, for 5 consecutive days at 30°C ambient temperature and 50% relative humidity and took either a placebo or Pro-CHO within 10 min after exercise for each day. Before and after training, PV at rest, heart rate (HR), and esophageal temperature (T(es)) during 30-min exercise at 65% of pretraining VO2peak in the same condition as training were determined. Also, the sensitivity of the chest sweat rate (ΔSR/ΔT(es)) and forearm vascular conductance (ΔFVC/ΔT(es)) in response to increased T(es) were determined. After training, PV and cardiac stroke volume (SV) at rest increased in both groups (P < 0.001) but the increases were twofold higher in Pro-CHO than CNT (P = 0.007 and P = 0.078, respectively). The increases in HR from 5 to 30 min and T(es) from 0 to 30 min of exercise were attenuated after training in both groups with greater attenuation in Pro-CHO than CNT (P = 0.002 and P = 0.072, respectively). ΔSR/ΔT(es) increased in CNT (P = 0.052) and Pro-CHO (P < 0.001) and the increases were higher in Pro-CHO than CNT (P = 0.018). ΔFVC/ΔT(es) increased in Pro-CHO (P < 0.001), whereas not in CNT (P = 0.16). Thus protein-CHO supplementation during 5-day training enhanced PV expansion and thermoregulatory adaptation and, thereby, the reduction in heat and cardiovascular strain in young men.

Effects of aerobic fitness on hypohydration-induced physiological strain and exercise impairment

AIM

Hypohydration exacerbates cardiovascular and thermal strain and can impair exercise capacity in temperate and warm conditions. Yet, athletes often dehydrate in exercise, are hypervolaemic and have less cardiovascular sensitivity to acute hypervolaemia. We tested the hypothesis that trained individuals have less cardiovascular, thermoregulatory and performance affect of hypohydration during exercise.

METHODS

After familiarization, six trained [VO(2 peak) = 64 (SD 8) mL kg(-1) min(-1)] and six untrained [O(2 peak) = 45 (4) mL kg(-1) min(-1)] males cycled 40 min at 70%O(2 peak) while euhydrated or hypohydrated by 1.5-2.0% body mass (crossover design), before a 40-min work trial with euhydration or ad libitum drinking (in Hypohydration trial), in temperate conditions (24.3 degrees C, RH 50%, v(a) = 4.5 m s(-1)). Baseline hydration was by complete or partial rehydration from exercise+heat stress the previous evening.

RESULTS

During constant workload, heart rate and its drift were increased in Hypohydration compared with Euhydration for Untrained [drift: 33 (11) vs. 24 beats min(-1) h(-1) (10), 95% CI 5-11] but not Trained [14 (3) vs. 13 beats min(-1) h(-1) (3), CI -2 to 3; P = 0.01 vs. Untrained]. Similarly, rectal temperature drift was faster in Hypohydration for Untrained only [by 0.57 degrees C h(-1) (0.25); P = 0.03 vs. Trained], concomitant with their reduced sweat rate (P = 0.05) and its relation to plasma osmolality (P = 0.03). Performance power tended to be reduced for Untrained (-13%, CI -35 to 2) and Trained (-7%, CI: -16 to 1), without an effect of fitness (P = 0.38).

CONCLUSION

Mild hypohydration exacerbated cardiovascular and thermoregulatory strain and tended to impair endurance performance, but aerobic fitness attenuated the physiological effects.

Protein and carbohydrate supplementation increases aerobic and thermoregulatory capacities

The incidence of heat illness and heat stroke is greater in older than younger people. In this context, exercise training regimens to increase heat tolerance in older people may provide protection against heat illness. Acute increases in plasma volume (PV) improve thermoregulation during exercise in young subjects, but there is some evidence that changes in PV in response to acute exercise are blunted in older humans. We recently demonstrated that protein-carbohydrate (Pro-CHO) supplementation immediately after a bout of exercise increased PV and plasma albumin content (Alb(cont)) after 23 h in both young and older subjects. We also examined whether Pro-CHO supplementation during aerobic training enhanced thermoregulation by increasing PV and Alb(cont) in older subjects. Older men aged 68 years exercised at moderate intensity, 60 min day(1), 3 days week(1), for 8 weeks, at 19 degrees C, and took either placebo (CNT; 0.5 kcal, 0 g protein kg(1)) or Pro-CHO supplement (Pro-CHO; 3.2 kcal, 0.18 g protein kg(1)) immediately after exercise. After training, we found during exercise at 30 degrees C that increases in oesophageal temperature (T(es)) were attenuated more in Pro-CHO than CNT and associated with enhanced cutaneous vasodilatation and sweating. We also confirmed similar results in young subjects after 5 days of training. These results demonstrate that post-exercise protein and CHO consumption enhance thermoregulatory adaptations especially in older subjects and provide insight into potential strategies to improve cardiovascular and thermoregulatory adaptations to exercise in both older and younger subjects.

Effects of mild calorie restriction and high-intensity interval walking in middle-aged and older overweight Japanese

We investigated whether a combination of mild calorie restriction (MCR) and high-intensity interval walking (HIW) improved physical fitness more than HIW alone in middle-aged and older overweight Japanese (40-69years old, BMI23.6kg/m(2)). Forty-seven women and 16 men were divided into MCR+HIW and HIW groups. All subjects performed HIW: 5 sets of 3-min low-intensity walking (40% peak aerobic capacity for walking, VO(2peak)) and 3-min high-intensity walking (70% VO(2peak)) per day, 4days per week, for 16weeks while energy expenditure was monitored with a tri-axial accelerometer. The MCR+HIW group consumed meal replacement formula (240kcal): a mixture of low-carbohydrates and -fat and high-protein, for either lunch or dinner everyday and therefore, had approximately 87% of the energy intake of the HIW group during the intervention period. Although the HIW group showed improvements in BMI, blood pressure, and several blood chemicals, the MCR+HIW group had greater improvement. Moreover, the medical expenditure for the 6months including the intervention period was 59% lower in the MCR+HIW group than in the HIW group. Our strategy of a short-term combination of MCR and HIW may thus prevent lifestyle-associated diseases and improve health in middle-aged and older overweight Japanese.