Effect of wearing clothes on oxygen uptake and ratings of perceived exertion while swimming.

For a comparative study between swimming in swimwear (control-sw) and swimming in clothes (clothes-sw), oxygen uptake (VO2) and ratings of perceived exertion (RPE) were measured. The subjects were six male members of a university swimming team. Three swimming strokes--the breaststroke, the front crawl stroke and the elementary backstroke--were applied. With regards to clothes-sw, swimmers wore T-shirts, sportswear (shirt and pants) over swimwear and running shoes. In both cases of control-sw and clothes-sw, the VO2 was increased exponentially with increased swimming speed. The VO2 of the subjects during the clothed tests did not exceed 1.4 times of that in the case of control-sw at swimming speeds below 0.3 m/s. As swimming speeds increased, VO2 difference in both cases increased. Consequently, VO2 in the clothed tests was equal to 1.5-1.6 times and 1.5-1.8 times of that in the swimwear tests at speeds of 0.5 and 0.7 m/s, respectively. At speeds below 0.6 m/s in clothes-sw, the breaststroke showed lower VO2 than the front crawl stroke, and the elementary backstroke showed higher VO2 than the other two swimming strokes. RPE increased linearly with %peak VO2. In addition, any RPE differences among the three swimming strokes were not shown in the control-sw tests. At an exercise intensity above 60 %peak VO2, clothed swimmers showed slightly higher RPE in the front crawl stroke compared to that in the two other swimming strokes.

Relationship among blood lactate and plasma catecholamine levels during exercise in acute hypoxia.

Five male subjects performed steady exercise on a cycle ergometer at an intensity of 60% maximal O2 uptake (VO2max) for 6 min on three separate occasions while breathing gas mixtures of 12,16 or 21% O2 in N2. Expired gas fractions, ventilation, heart rate, arterial O2 saturation (SaO2), blood lactate (La) and plasma catecholamines (epinephrine: E and norepinephrine: NE) were measured. O2 uptake (VO2) was calculated for the last minute of exercise. Blood samples were drawn at rest and immediately after exercise. By inspiring hypoxic gas mixtures, the SaO2 value decreased during exercise to 85.0 +/- 5.4 (16%) and 66.4 +/- 4.1 (12%) from 95.0 +/- 0.1 in normoxia. VO2 during exercise was not different among the three conditions. Exercise-induced La accumulation was increased by hypoxia. E and NE during exercise were not affected by hypoxia statistically. There was a significant correlation between La and E (P < 0.01) and between La and NE (P < 0.01) during exercise in the three conditions. The present findings suggest a relationship between glycogen metabolism and sympathoadrenal activity which results in an increase of plasma catecholamines during exercise in humans acutely exposed to hypoxia.