Aging and assessment of physiological strain during exercise-heat stress.
The purpose of this study was to evaluate the physiological strain index (PSI) for different age groups during exercise-heat stress (EHS). PSI was applied to three different databases. First, from young and middle-age men (21 +/- 2 and 46 +/- 5 yr, respectively) matched (n = 9 each, P > 0.05) for maximal aerobic power. Subjects were heat acclimated by daily treadmill walking for two 50-min bouts separated by 10-min rest for 10 days in a hot-dry environment [49 degrees C, 20% relative humidity (RH)]. The second database involved a group (n = 8) of young (YA) and a group (n = 7) of older (OA) men (26 +/- 1 and 69 +/- 1 yr, respectively) who underwent 16 wk of aerobic training and two control groups (n = 7 each) who were matched for age to YA and OA. These four groups performed EHS at 36 degrees C, 40% RH on a cycle ergometer for 60 min at 60% maximal aerobic power before and after training. The third database was obtained from three groups of postmenopausal women and a group of 10 men. Two groups of women (n = 8 each) were undergoing hormone replacement therapy, estrogen or estrogen plus progesterone, and the third group (n = 9) received no hormone replacement. Subjects were over 50 yr and performed the same EHS: exercising at 36 degrees C, 40% RH on a cycle ergometer for 60 min. PSI assessed the strain for all three databases and reported differences were significant at P < 0.05. This index rated the strain in rank order, whereas the postacclimation and posttraining groups were assessed as having less strain than the preacclimation and pretraining groups. Furthermore, middle-aged women on estrogen replacement therapy had less strain than estrogen + progesterone and no hormone therapy. PSI evaluation was extended for men and women of different ages (50-70 yr) during acute EHS, heat acclimation, after aerobic training, and inclusive of women undergoing hormone replacement therapy.
Moran
Daniel S
DS
US Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760-5007, USA. dmoran@sheba.health.gov.il
Kenney
W Larry
WL
Pierzga
Jane M
JM
Pandolf
Kent B
KB
D000328:Adult; D000375:Aging / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology; D004947:Esophagus; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000008:administration & dosage; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017698:Postmenopause / Q000502:physiology; D011374:Progesterone / Q000008:administration & dosage; D012007:Rectum
D004967:Estrogens; D011374:Progesterone