The influence of prior exercise at anaerobic threshold on decompression sickness

This study was conducted to examine the effects of exercise prior to decompression on the incidence of altitude decompression sickness (DCS). In a balanced, two-period, crossover trial, 39 healthy individuals (29 males, 10 females) of mean (S.D.) age 32.5 (7.7) years and body mass index 23.7 (3.4) were each exposed twice, without denitrogenation, to an altitude of 6,400 m (21,000 ft) in a hypobaric chamber. Under the experimental condition, subjects exercised at their predetermined anaerobic threshold levels for 30 min each day for 3 d prior to altitude exposure; the other condition was a non-exercise control. Under both conditions, subjects performed exercise simulating space extravehicular activities at altitude for a period of 3 h, while breathing 100% oxygen. There were nine preferences (untied responses) for DCS, four under control and five under experimental conditions; all were Type I, pain-only bends. No carryover effect between exposures was detected, and the test for treatment differences showed p = 0.56 (95% confidence interval = 0.34-0.58) for symptoms. No significant difference in DCS preferences was found after subjects exercised up to their anaerobic threshold levels during the days prior to decompression.