scholarly journals Psychrometric limits and critical evaporative coefficients for exercising older women

2020 ◽  
Vol 129 (2) ◽  
pp. 263-271 ◽  
Author(s):  
W. Larry Kenney
Keyword(s):  
Older Women ◽  
Heat Balance ◽  
Moderate Intensity ◽  
Evidence Based ◽  
Moderate Intensity Exercise ◽  
Metabolic Heat ◽  
Safety Interventions ◽  
Environmental Limits ◽  
Hot Environments ◽  
Heat Events

This study is the first to describe, graphically and quantitatively, critical environmental limits for women between the ages of 62 and 80 yr based on the biophysics of heat exchange. These psychrometric limit lines define combinations of ambient temperature and humidity above which human heat balance cannot be maintained for a given metabolic heat production. These limits, and associated critical evaporative coefficients ( Ke′), can be used to model low- to moderate-intensity exercise responses in hot environments and have directly translatable data that can be used for evidence-based policy decisions, to prepare for impending heat events, and for implementation of other safety interventions.

Oxygen uptake kinetics in endurance-trained and untrained postmenopausal women

2013 ◽  
Vol 38 (2) ◽  
pp. 154-160 ◽  
Author(s):  
Shilpa Dogra ◽  
Matthew D. Spencer ◽  
Juan M. Murias ◽  
Donald H. Paterson
Keyword(s):  
Heart Rate ◽  
Oxygen Uptake ◽  
Older Women ◽  
Near Infrared ◽  
Ventilatory Threshold ◽  
Vastus Lateralis ◽  
Hemoglobin Concentration ◽  
Oxygen Uptake Kinetics ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise

The rate of adjustment for pulmonary oxygen uptake (τV̇O2p) is slower in untrained and in older adults. Near-infrared spectroscopy (NIRS) has shed light on potential mechanisms underlying this in young men and women and in older men; however, there is no such data available in older women. The purpose of this study was to gain a better understanding of the mechanisms of slower τV̇O2p in older women who were either endurance-trained or untrained. Endurance-trained (n = 10; age, 62.6 ± 1.0 years) and untrained (n = 9; age, 69.1 ± 2.2 years) older women attended 2 maximal and 2 submaximal (90% of ventilatory threshold) exercise sessions. Oxygen uptake (V̇O2) was measured breath by breath, using a mass spectrometer, and changes in deoxygenated hemoglobin concentration of the vastus lateralis ([HHb]) were measured using NIRS. Heart rate was measured continuously with a 3-lead electrocardiogram. τV̇O2p was faster in trained (35.1 ± 5.5 s) than in untrained (57.0 ± 8.1 s) women. The normalized [HHb] to V̇O2 ratio, an indicator of muscle O2 delivery to O2 utilization, indicated a smaller overshoot in trained (1.09 ± 0.1) than in untrained (1.39 ± 0.1) women. Heart rate data indicated a faster adjustment of heart rate in trained (33.0 ± 13.0) than in untrained (68.7 ± 14.1) women. The pairing of V̇O2p data with NIRS-derived [HHb] data indicates that endurance-trained older women likely have better matching of O2 delivery to O2 utilization than older untrained women during moderate-intensity exercise, leading to a more rapid adjustment of V̇O2p.

Effect of age on heat-activated sweat gland density and flow during exercise in dry heat

1987 ◽  
Vol 63 (3) ◽  
pp. 1089-1094 ◽  
Author(s):  
R. K. Anderson ◽  
W. L. Kenney
Keyword(s):  
Older Women ◽  
Sweat Gland ◽  
Age Groups ◽  
Whole Body ◽  
Moderate Intensity ◽  
Exercise Session ◽  
Sweat Glands ◽  
Moderate Intensity Exercise ◽  
Age Related ◽  
Eccrine Glands

Physiological responses of eight postmenopausal older women (age 52–62 yr) and eight younger women (age 20–30 yr) were compared during moderate intensity exercise in a hot dry environment (48 degrees C dry bulb, 25 degrees C wet bulb). The age groups were matched on the basis of maximal O2 consumption (VO2max), body surface area, and body fatness. After heat acclimation the women walked at 40% VO2max for up to 2 h in the hot dry environment while heart rate (HR), rectal temperature (Tre), mean skin temperature (Tsk), whole-body sweating rate (Msw), and local sweating rates (msw; forearm, chest, and scapula) were measured. Additionally, the density of heat-activated sweat glands (HASG) was determined and average sweat gland flow (SGF) was calculated for the scapular area. Although no differences between age groups were found in HR response (when analyzed as percent of maximal HR) or Tsk, the older women had a significantly higher Tre throughout the heat-exercise session. The greater heat storage of the older women may be explained by their significantly lower Msw and msw. There were no differences between the younger and older women in the density of HASG after 30 min; therefore, the lower msw reflects a diminished output per HASG rather than a decrease in the number of sweat glands recruited. The diminished thermoregulatory ability of the older women, unrelated to differences in VO2max, appears to reflect either 1) a diminished response of the sweat glands to central and/or peripheral stimuli, or 2) an age-related structural alteration in the eccrine glands or surrounding skin cells.

Metabolism- and sex-dependent critical WBGT limits at rest and during exercise in the heat

2021 ◽  
Author(s):  
S. Tony Wolf ◽  
Mireille A. Folkerts ◽  
Rachel M. Cottle ◽  
Hein A.M. Daanen ◽  
W. Larry Kenney
Keyword(s):  
Sex Differences ◽  
Thermal Environment ◽  
Water Vapor Pressure ◽  
Absolute Intensity ◽  
Body Core Temperature ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Wet Bulb Globe Temperature ◽  
Globe Temperature ◽  
Environmental Limits

Critical environmental limits are environmental thresholds above which heat gain exceeds heat loss and body core temperature (Tc) cannot be maintained at equilibrium. Those limits can be represented as critical wet-bulb globe temperature (WBGTcrit), a validated index that represents the overall thermal environment. Little is known about WBGTcrit at rest and during low-to-moderate intensity exercise, or sex differences in WBGTcrit, in unacclimated young adults. The following hypotheses were tested: (1) WBGTcrit progressively decreases as metabolic heat production (Mnet) increases, (2) no sex differences in WBGTcrit occur at rest, and (3) WBGTcrit is lower during absolute-intensity exercise but higher at relative intensities in women compared to men. Thirty-six participants (19M/17W; 23±4 yr) were tested at rest, during light, absolute-intensity exercise (10 W), or during moderate, relative-intensity exercise (30% V̇O2max) in an environmental chamber. Dry-bulb temperature was clamped as relative humidity or ambient water vapor pressure was increased until an upward inflection was observed in Tc (rectal or esophageal temperature). Sex-aggregated WBGTcrit was lower during 10 W (32.9±1.7°C, P<0.0001) and 30% V̇O2max (31.6±1.1°C, P<0.0001) exercise vs. rest (35.3±0.8°C), and lower at 30% V̇O2max vs. 10 W (P=0.01). WBGTcrit was similar between sexes at rest (35.6±0.8°C vs. 35.0±0.8°C, P=0.83), but lower during 10 W (31.9±1.7°C vs. 34.1±0.3°C, P<0 .01) and higher during 30% V̇O2max (32.4±0.8°C vs. 30.8±0.9°C, P=0.03) exercise in women vs. men. These findings suggest that WBGTcrit decreases as Mnet increases, no sex differences occur in WBGTcrit at rest, and sex differences in WBGTcrit during exercise depend upon absolute vs. relative intensities.

Psychrometric limits and critical evaporative coefficients for unacclimated men and women

2002 ◽  
Vol 92 (6) ◽  
pp. 2256-2263 ◽  
Author(s):  
W. Larry Kenney ◽  
Michael J. Zeman
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Heat Production ◽  
Heat Balance ◽  
Water Vapor Pressure ◽  
Metabolic Heat Production ◽  
Maximal Aerobic Capacity ◽  
Men And Women ◽  
Metabolic Heat ◽  
Environmental Limits

Critical environmental limits, defined as those above which heat balance cannot be maintained for a given metabolic heat production, have not been determined for unacclimated subjects. To characterize critical environmental limits and to derive evaporative heat exchange coefficients ( K e′) for unacclimated young men ( n = 11) and women ( n = 10), subjects of average aerobic fitness walked at 30% maximal aerobic capacity in an environmental chamber. Critical environmental conditions were defined as the psychrometric loci of dry-bulb temperature and water vapor pressure at which core (esophageal) temperature was forced out of equilibrium (heat gain exceeded heat loss). Compared with the men in our study, the women had significantly higher critical environmental limits ( P < 0.001) in warm (34–38°C), humid (>60%) environments, a function of their lower absolute metabolic heat production at the fixed relative exercise intensity. Isotherms constructed from biophysical models closely fit the data in this range of environments but underestimated empirically determined critical limits in hotter, drier environments. Sex-specific values of K e′ were derived by partial calorimetry in the critical water vapor pressure environments, in which full skin wettedness occurred. There were no sex differences for K e′ (men = 17.4, 15.5, and 14.2 W · m−2 · Torr−1 and women = 16.8, 15.5, and 14.2 W · m−2 · Torr−1 at 34, 36, and 38°C, respectively). These K e′ values were lower than those previously published for fully heat-acclimated men (18.4 W · m−2 · Torr−1 at 36°C) and women (17.7 W · m−2 · Torr−1 at 36°C and 15.5 W · m−2 · Torr−1 at 38°C) and may be used to model heat balance responses for unacclimated men and women working in hot environments.

scholarly journals Effect of healthy aging and sex on middle cerebral artery blood velocity dynamics during moderate-intensity exercise

2018 ◽  
Vol 315 (3) ◽  
pp. H492-H501 ◽  
Author(s):  
Jaimie L. Ward ◽  
Jesse C. Craig ◽  
Yumei Liu ◽  
Eric D. Vidoni ◽  
Rebecca Maletsky ◽  
...  
Keyword(s):  
Middle Cerebral Artery ◽  
Older Women ◽  
Cerebral Artery ◽  
Blood Velocity ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Cerebrovascular Function ◽  
Age Related ◽  
Young Subjects ◽  
Response To Exercise

Blood velocity measured in the middle cerebral artery (MCAV) increases with finite kinetics during moderate-intensity exercise, and the amplitude and dynamics of the response provide invaluable insights into the controlling mechanisms. The MCAV response after exercise onset is well fit to an exponential model in young individuals but remains to be characterized in their older counterparts. The responsiveness of vasomotor control degrades with advancing age, especially in skeletal muscle. We tested the hypothesis that older subjects would evince a slower and reduced MCAV response to exercise. Twenty-nine healthy young (25 ± 1 yr old) and older (69 ± 1 yr old) adults each performed a rapid transition from rest to moderate-intensity exercise on a recumbent stepper. Resting MCAV was lower in older than young subjects (47 ± 2 vs. 64 ± 3 cm/s, P < 0.001), and amplitude from rest to steady-state exercise was lower in older than young subjects (12 ± 2 vs. 18 ± 3 cm/s, P = 0.04), even after subjects were matched for work rate. As hypothesized, the time constant was significantly longer (slower) in the older than young subjects (51 ± 10 vs. 31 ± 4 s, P = 0.03), driven primarily by older women. Neither age-related differences in fitness, end-tidal CO2, nor blood pressure could account for this effect. Thus, MCAV kinetic analyses revealed a marked impairment in the cerebrovascular response to exercise in older individuals. Kinetic analysis offers a novel approach to evaluate the efficacy of therapeutic interventions for improving cerebrovascular function in elderly and patient populations. NEW & NOTEWORTHY Understanding the dynamic cerebrovascular response to exercise has provided insights into sex-related cerebrovascular control mechanisms throughout the aging process. We report novel differences in the kinetics response of cerebrovascular blood velocity after the onset of moderate-intensity exercise. The exponential increase in brain blood flow from rest to exercise revealed that 1) the kinetics profile of the older group was blunted compared with their young counterparts and 2) the older women demonstrated a slowed response.

Moderate and heavy oxygen uptake kinetics in postmenopausal women

2009 ◽  
Vol 34 (6) ◽  
pp. 1065-1072 ◽  
Author(s):  
Liza Stathokostas ◽  
John M. Kowalchuk ◽  
Robert J. Petrella ◽  
Donald H. Paterson
Keyword(s):  
Oxygen Uptake ◽  
Postmenopausal Women ◽  
Older Women ◽  
Ventilatory Threshold ◽  
Hormone Replacement ◽  
Oxygen Uptake Kinetics ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Repeated Exercise ◽  
Exercise Transitions

The lack of estrogen in postmenopausal women not using hormone replacement therapy (HRT), compared with those using HRT, may reduce submaximal blood flow during exercise and result in an oxygen delivery limitation constraining oxygen uptake (VO2) kinetics. The adaptation of pulmonary VO2 (VO2p) during the transition to exercise in older women was examined in this study. Thirty-one healthy postmenopausal women (mean age, 61 ± 6 years), 15 not using HRT and 16 using HRT, performed repeated exercise transitions (6 min) on a cycle, to work rates corresponding to 80% of estimated ventilatory threshold (moderate-intensity exercise) and to Δ50 (heavy-intensity exercise). There was no difference in moderate-intensity τVO2p between non-HRT (40 ± 9 s) and HRT (41 ± 9 s) women. Similarly, there was no difference in heavy-intensity τVO2p between non-HRT (44 ± 8 s) and HRT (45 ± 8 s) women. Thus, HRT did not affect the slowing of VO2 kinetics of older women.

scholarly journals The effect of moderate-intensity exercise on nightly variability in objectively measured sleep parameters among older women

2017 ◽  
Vol 17 (4) ◽  
pp. 459-469 ◽  
Author(s):  
Charity B. Breneman ◽  
Christopher E. Kline ◽  
Delia S. West ◽  
Xuemei Sui ◽  
Ryan R. Porter ◽  
...  
Keyword(s):  
Older Women ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Sleep Parameters ◽  
Objectively Measured

scholarly journals Thermoregulation is not impaired in breast cancer survivors during moderate‐intensity exercise performed in warm and hot environments

2021 ◽  
Vol 9 (14) ◽  
Author(s):  
Rebecca L. Relf ◽  
Ben J. Lee ◽  
Gregor Eichhorn ◽  
Melanie S. Flint ◽  
Louisa Beale ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Survivors ◽  
Breast Cancer Survivors ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Hot Environments

Fluid ingestion is more effective in preventing hyperthermia in aerobically trained than untrained individuals during exercise in the heat

2013 ◽  
Vol 38 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Ricardo Mora-Rodriguez ◽  
Nassim Hamouti ◽  
Juan Del Coso ◽  
Juan F. Ortega
Keyword(s):  
Heart Rate ◽  
Heat Production ◽  
Fluid Replacement ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Fluid Ingestion ◽  
Metabolic Heat ◽  
Heat Production Rate ◽  
Cardiovascular Strain ◽  
Aerobically Trained

It is unclear if fluid ingestion during exercise in the heat alleviates the thermoregulatory and cardiovascular strain similarly in aerobically trained and untrained individuals. It is also unknown at what exercise intensity the effects of rehydration are greater. Ten aerobically trained (T) and 10 healthy untrained (UT) subjects ([Formula: see text]O2peak, 60 ± 6 vs. 44 ± 3 mL O2·kg−1·min−1, respectively; P < 0.05) pedalled in a hot, dry environment (36 ± 1 °C; 25% ± 2% relative humidity; airflow, 2.5 m·s−1) at 40%, 60%, and 80% [Formula: see text]O2peak while ingesting fluids (Fluid). The results were compared with those from our previous study [Mora-Rodriguez et al., Eur. J. Appl. Physiol. 109(5): 973–981 (2010)] with no fluid ingestion (No Fluid). Subjects were not heat-acclimated. At 40% [Formula: see text]O2peak, Fluid reduced rectal temperature (TRE) in T and UT (0.31 ± 0.08 and 0.32 ± 0.07 °C; respectively). At 60% [Formula: see text]O2peak, Fluid reduced TRE in T more than in UT (0.30 ± 0.10 °C vs. 0.18 ± 0.10 °C; P < 0.05) but had no effect at 80% [Formula: see text]O2peak in any group. At similar relative intensity, heart rates (HR) were similar between groups. Fluid lowered heart rate (i.e., HR) similarly in the T and UT at 40% and 60% [Formula: see text]O2peak (11% and 6%, respectively; P < 0.05) but not at 80% [Formula: see text]O2peak (P > 0.05). At similar metabolic heat production (i.e., 60% for T vs. 80% [Formula: see text]O2peak for UT), Fluid lowered TRE only in the T individuals (P < 0.05). In summary, rehydration during low- and moderate-intensity exercise reduces TRE and HR more than during high-intensity exercise (80% [Formula: see text]O2peak) in T and UT subjects. Fluid replacement is more effective on preventing the rise in TRE in T than in UT individuals during moderate-intensity exercise (60% [Formula: see text]O2peak), as well as when exercising at a similar heat production rate.

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