Barbara A. Avellini

Cardio-Respiratory Physical Training in Water and on Land,

SummaryFifteen unconditioned young men, who were similar in maximal aerobic power (VO2 max), were divided into three groups (n=5 each) and physically trained for one month on a cycle ergometer either on land (I) or immersed to the neck in water of either 32‡ C (II) or 20‡ C (III) to determine if physical training (PT) in water and air differ. PT consisted of one-hour daily exercise, 5 times/wk, with exercise intensity readjusted each week to maintain a constant training stimulus of ~ 75% VO2 max (determined on land). Throughout the training period, heart rates (fc) of III averaged 20 and 10 beats·min−1 less than I and II, respectively, despite working at the same VO2 and % VO2 max. Training elicited a 16% increase in VO2 max in I compared to increases of 13 and 15% for II and III, respectively. It was concluded that PT in water produces similar physiological adaptations as does training on land. In cold water, VO2 max is improved despite training with fc significantly lower than that on land.

Heat balance and transfer in men and women exercising in hot-dry and hot-wet conditions*

Sex-related differences in heat balance and transfer were studied in nine female and ten male heat-acclimatized subjects exposed to two hot-dry (HD) conditions(49°C, 20% rh; 54°C, 10% rh) and three hot-wet (H W) conditions (32°C, 80% rh; 35°C, 90% rh; 37°C, 80%rh). Exposures lasted 120min: l0min rest, 50min walk, l0min rest, 50min walk. Walking speed was 1 34 ms-1 (level), and for 49°C, 20% rh, in addition, 1-34ms-l, 5% grade. No sex-related differences were found in metabolic heat production (M), nor in heat exchange by radiation and convection (R + C)or evaporation (E), when expressed per unit body weight (wt). However, E per unit body surface area (A D) was lower in females by 9–13% (P<0 05 in all HD conditions and for the 32°C, 80% rh condition) due to their lower M/A D, and 4-6% lower (R + C)/A D in HD. Core-to-periphery heat conductance was similar in both sexes despite a lower core-to-skin temperature gradient for women in HD. It was suggested that women have an advantage over men in heat transfer ...

Scheduling rest for consecutive light and heavy work loads under hot ambient conditions.

Three male and three female heat-acclimated subjects participated in a series of five testing sessions aimed at validating a resting period which was assigned to follow work under warm-humid (Tdb 36°C, Twb 31°C) and hot-dry (Tdb 50°C, Twb 25°C) ambient conditions. Each working period consisted of 25 min of walking at 30% [Vdot]o2max followed by five minutes of carrying a load uphill at 75% [Vdot]o2max. The working period was based on the expected HR as it could be derived from: (1) the work-specific HR as determined from the linear relationship between % [Vdot]o2max and HR; (2) the heat-induced increments in HR; and (3) the endurance limits imposed by the age-dependent HRmax. Each 30 min of work was followed by 30 min of rest either under the same ambient conditions as for the working period, or under neutral ambient conditions. Judged by the levelling off of HR and by setting the limits of the Tre rise to 38°C during the consecutive walking periods, only the resting under the neutral conditions proved ad...

Scheduling Cycles of Work for Carrying under Heat Stress

Five minutes of carrying loads uphill were assigned to three female and three male heat acclimated subjects. The carrying (75% ), both of which were performed under warm-humid Tdb 36°C, Twb 31°C, and hot-dry Tdb 50°C, Twb 25°C, ambient conditions. Thirty minutes of rest were allowed after each 30 minutes of work. The resting conditions were either the same as those for the working periods or under neutral ambient conditions. Judged by the rise in HR and in Tre, and setting the limits of Tre to 38°C during the walking, the schedule was adequate only when resting was under the neutral ambient conditions, it was partially adequate for resting under the hot-dry ambient conditions, but completely inadequate for resting under the warm-humid conditions.