Exercise Tolerance in a Hot and Humid Climate in Heat-Acclimatized Girls and Women

Abstract

This study compared physiological responses associated with exercise tolerance in girls (G) and women (W) of similar fitness and heat acclimatization level during exercise in a hot and humid outdoor environment (33.4 degrees C and 55.1 % RH; WBGT = 29.9 +/- 0.2 degrees C). Nine pre-menarcheal G (age = 11.3 yr) and nine W (age = 26.8 yr), matched for aerobic capacity and heat acclimatization level, performed a cycling session at 60 % VO2max until fatigue. A sports drink was provided periodically to prevent dehydration. Tolerance time was not different between the groups (G = 56.9 +/- 6.3, W = 76.5 +/- 9.9 min, p > 0.05). During exercise, sweat rate (G = 9.1 +/- 1.1, W = 12.0 +/- 1.1 ml.m(-2).min(-1)), the increase in rectal temperature [T(re)] (G = 0.9 +/- 0.1, W = 1.1 +/- 0.1 degrees C), and heat storage (G = 10.6 +/- 5.3, W = 20.5 +/- 4.5 W.m(-2)) did not differ between the groups. At fatigue, T(re) (G = 38.2 +/- 0.1, W = 38.4 +/- 0.1 degrees C), heart rate (G = 167.3 +/- 7.3, W = 171 +/- 3.3 beats.min(-1)), stroke index (G = 48.3 +/- 1.5, W = 52.4 +/- 1.8 ml.m(-2)), and forearm skin blood flow (G = 9.5 +/- 1.3, W = 11.7 +/- 1.5 ml.100 ml(- 1).min(-1)) did not differ between the groups. Similar to women, the main reasons reported by girls to stop exercising in the heat were localized leg fatigue and gluteus muscle discomfort. We conclude that heat-acclimatized girls exhibit an adequate cardiovascular and thermoregulatory adjustment while exercising in a hot and humid outdoor environment when hypohydration is prevented.

Repeated-bout exercise in the heat in young athletes: physiological strain and perceptual responses

“…Although the preexercise urine specific gravity measures (Table 2) might suggest otherwise (higher at the start of bout 2), our subjects could have been better hydrated at the beginning of exercise bout 2 (compared with bout 1, given the between-bouts complete rehydration protocol described in METHODS), which has been shown to reduce physiological strain and enhance heat tolerance in children and adolescents (6,8,17,19,45,47). Urine specific gravity generally provides a valid indication of hydration status (5), although urine osmolality is also used and sometimes preferred, especially when plasma osmolality is not available (53,62).…”

“…hydration; recovery; risk management; thermoregulation; youth sports A SHORT RECOVERY PERIOD between same-day rounds of tournament competition is common practice in organized youth sports. With the additional effects imposed by a hot environment on cardiovascular and thermal strain, performance, and exertional heat injury risk (1,2,4,8,9,14,21,22,24,25,45,47,48), the ability to perform safely and effectively through multiple strenuous same-day competition bouts in the heat can be challenging for young athletes (8, 16). The apparent cumulative demands can often result in poor performance or complete withdrawal from play.…”

Gender- and Sex-specific Sports-related Injury Research in Emergency Medicine: A Consensus on Future Research Direction and Focused Application

“…At similar levels of fitness and exertional states, male and female youth and adults have shown similar predispositions toward heat illness. [50][51][52][53] Both highly trained elite athletes and all ranges of amateur athletes are at risk. However, a paucity of research evaluates exertional heat illness in presentation and degree of severity as it manifests in men and women.…”

Heat injury in youth sport: Table 1

“…There are few recent well-controlled exercise physiology studies of heat and exercise in children that are directly applicable to real-world field conditions 6. Actual observational studies of children exercising under field conditions are typically limited to heat injury precursor conditions, such as mild dehydration or subclinical increases in core body temperature 14 15 16. Thus, our knowledge of risk factors for heat injury is largely dependent on a group of exercise physiology studies, many of which have been limited to adults and were conducted in laboratory settings that may or may not simulate real field conditions.…”