Peak oxygen uptake during arm stroke under a hypobaric hypoxic condition.

The purpose of this study was to examine the limiting factor for swimming by measuring peak oxygen uptake (peak VO2) during front crawl (C) and arm stroke (A) under a hypobaric hypoxic condition. Seven-trained swimmers (age; 19-21 yrs, 100 m free style event; 57.2 +/- 2.5 secs) were measured twice under a normal (N) (751 mmHg) and a hypobaric hypoxic (H) (602 mmHg) condition in a chamber where atmospheric pressure was regulated. Water flow rate started at 0.80 m.sec-1 and was increased by 0.05 m.sec-1 every 2 min up to 1.00 m.sec-1. Subsequently, flow rate was increased by 0.05 m.sec-1 every minute until exhaustion. VO2 was measured with an automatic analyzer. The peak heart rate under N was not significantly different from that under H in both C (N; 190 +/- 9, H; 184 +/- 6 beats.min-1) and A (N; 180 +/- 6, H; 181 +/- 6 beats.min-1). Peak VO2 values during A (N; 3.42 +/- 0.27, H; 3.08 +/- 0.19 l.min-1) were significantly lower by 15-20% than those during C (N; 4.18 +/- 0.18, H; 3.65 +/- 0.11 l.min-1) for both N and H (p less than 0.01). Peak VO2 values under H were significantly lower than those under N during both C and A (p less than 0.01). There was no significant difference in the magnitude of decrease in peak VO2 between C (12.0 +/- 3.4%) and A (9.8 +/- 3.8%) under H. This ratio of decrease agrees with previous investigations that studied centrally limited exercise, such as running and cycling, under similar levels of hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)