Heat tolerance of exercising lean and heavy prepubertal girls

Haymes, Emily M.; Buskirk, E. R.; Hodgson, J. L.; Lundegren, Herberta M.; Nicholas, W. Channing

doi:10.1152/jappl.1974.36.5.566

Cited by 65 publications

(46 citation statements)

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“…The adequate thermoregulation demonstrated by the boys is consistent with previous studies using neutral or mild heat conditions (Gullestad 1975;Davies 1981;Docherty et al 1986;Delamarche et al 1990). Nevertheless, there have been conflicting reports that children have a greater increase in core temperature or heat storage when ambient temperature is more than 10°C higher than skin temperature (Wagner et al 1972;Haymes et al 1974;Drinkwater et al 1977;Bar-Or 1989). It should be noted that regional differences were found in the age-related differences in the effector responses of LDF and SGO, despite effective regulation of core temperature by the boys.…”

Section: Discussionmentioning

confidence: 99%

Thermoregulatory responses of prepubertal boys and young men during moderate exercise

Shibasaki

Inoue

Kondo

et al. 1997

European Journal of Applied Physiology

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Seven prepubertal boys (aged 10-11 years) and eleven young men (aged 21-25 years), matched for skinfold thickness and maximal oxygen uptake (VO2max) per unit of mass, cycled at an intensity of approximately 40% VO2max for 45 min in a warm condition (30 degrees C, 45% relative humidity). During exercise no age-related differences were observed for the increases in rectal temperature (Tre) and heart rate (HR), although the absolute Tre and HR were significantly greater for the boys because of a higher initial baseline (P < 0.05). Total body sweating rate [181 (SEM 12) vs 245 (SEM 12) g.m-2(.)45 min-1; P < 0.002] and local sweating rates (msw) on chest, back, and forearm were significantly lower for the boys (P < 0.001), as was metabolic heat production [203 (SEM 9) vs 276 (SEM 9) W.m-2; P < 0.01]. The lower msw in the boys was due to a lower output per activated sweat gland, even though they had a higher activated sweat gland density regardless of site. In contrast, cutaneous blood flow by laser Doppler flowmetry (LDF) in the boys was significantly greater on the chest and back, compared to the men (P < 0.003). The age-related differences in cutaneous vascular conductance (CVC) were more marked because of lower mean arterial pressure in the boys during exercise. However, forearm LDF and CVC were significantly lower for the boys (P < 0.008). No significant differences in LDF among sites were observed for the boys, whereas for the men LDF on the forearm was significantly greater than on the chest and back (P < 0.01). The boys showed lower mean skin temperatures (especially on the back and chest despite greater increments of LDF) after starting to sweat, whereas the men remained unchanged, suggesting that the heat loss on the trunk in the boys was promoted by greater increments of LDF despite lower msw, compared to the young men. It was concluded that during moderate exercise in an air temperature at 30 degrees C, prepubertal boys could thermoregulate as efficiently as young men by greater vasodilatation on their trunk despite lower msw. Furthermore regional differences may exist in the maturation-related modification of vasodilatation.

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Section: Discussionmentioning

confidence: 99%

Thermoregulatory responses of prepubertal boys and young men during moderate exercise

Shibasaki

Inoue

Kondo

et al. 1997

European Journal of Applied Physiology

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“…The authors explained this in terms of a higher heat load (when T a was considerably above Ts) placed on the lean subjects, who had a 32.5% larger Ab/m ratio than the obese subjects. Both Wagner et al (1972) and Haymes et al (1974) presented evidence that children, who have larger Ab/m ratios than adults, were exposed to a higher heat stress and were therefore less tolerant of exercise at 32.2°C Tef f (and T a Ts). Strydom, Wyndham and Benade (1971) observed that men weighing less than 50 kg were less tolerant of work in the heat and more difficult to acclimate than men of normal body weight.…”

Section: Discussionmentioning

confidence: 99%

Effects of daily and intermittent exposures on heat acclimation of women

Fein¹,

Haymes²,

Buskirk

1975

Int J Biometeorol

Self Cite

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A B S T R A C T . -Twelve women, who differed in physical condition and body size, w e r e heat a c c l i m a t e d utilizing e i t h e r a daily or i n t e r m i t t e n t ( e v e r y 3rd day) e xp o s u r e p a t t e r n in an e n v i r o n m e n t a l c h a m b e r . The w o m e n walked for 100 rain at 5.2 km~h up a 2.5% g r a d e on a m o t o r -d r i v e n t r e a d m i l l C l i m a t i c c h a m b e r c o nditions w e r e 4 6 . 5°C Ta, 2 4 . 5°C Twb +_ 0 . 5°C . Although individual a c c l i m a t i o n v a r i e d , significant r e d u c t i o n in heat s t r a i n was o b s e r v e d in all subjects, e . g . , the ability to c o m p l e t e the a s s i g n e d t a s k with i n c r e a s i n g ease, a d e c r e a s e in working h e a r t rate, a d e c r e a s e in r e c t a l t e m p e r a t u r e r i s e , a d e c r e a s e in m e a n skin t e m p e r a t u r e , an i n c r e a s e in sweat rate, an i n c r e a s e in e v a p o r a t i v e rate, and a d e c r e a s e in heat s t o r a g e . The p a t t e r n of heat e x p o s u r e s , daily or e v e r y t h i r d day, had no d i s c e r n i b l e effect on the r a t e of heat a c c l i m a t i o n . The highly conditioned s u b j e c t s showed l e s s physiological s t r a i n , p a r t i c u l a r l y d u r i n g the f i r s t few heat e x p o s u r e s , and m a i n t a i n e d s o m e r e l a t i v e advantage throughout the s e r i e s of I0 e x p o s u r e s . Body size, in the r a n g e studied, a p p e a r e d to e x e r t little influence on the amount of t h e r m a l s t r a i n . "

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“…[8][9][10][11][12][13] However, more recent studies, in which both groups were exposed to equal relative intensity exercise workloads and environmental conditions while minimizing dehydration, have compared 9-to 12-year-old boys and girls to similarly fit and heatacclimatized adults. These newer findings indicate that children and adults have similar rectal and skin temperatures, cardiovascular re-sponses, and exercise-tolerance time during exercise in the heat.…”

Section: Introductionmentioning

confidence: 99%

Climatic Heat Stress and Exercising Children and Adolescents

Bergeron¹,

Devore²,

Rice³

2011

Pediatrics

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Results of new research indicate that, contrary to previous thinking, youth do not have less effective thermoregulatory ability, insufficient cardiovascular capacity, or lower physical exertion tolerance compared with adults during exercise in the heat when adequate hydration is maintained. Accordingly, besides poor hydration status, the primary determinants of reduced performance and exertional heat-illness risk in youth during sports and other physical activities in a hot environment include undue physical exertion, insufficient recovery between repeated exercise bouts or closely scheduled same-day training sessions or rounds of sports competition, and inappropriately wearing clothing, uniforms, and protective equipment that play a role in excessive heat retention. Because these known contributing risk factors are modifiable, exertional heat illness is usually preventable. With appropriate preparation, modifications, and monitoring, most healthy children and adolescents can safely participate in outdoor sports and other physical activities through a wide range of challenging warm to hot climatic conditions.

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Heat tolerance of exercising lean and heavy prepubertal girls

Cited by 65 publications

References 0 publications

Thermoregulatory responses of prepubertal boys and young men during moderate exercise

Thermoregulatory responses of prepubertal boys and young men during moderate exercise

Effects of daily and intermittent exposures on heat acclimation of women

Climatic Heat Stress and Exercising Children and Adolescents

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