CHANGES IN PLASMA-VOLUME FOLLOWING INTENSE INTERMITTENT EXERCISE IN NEUTRAL AND HOT ENVIRONMENTAL-CONDITIONS

Background. The purpose of the present investigation was to examine th e effect of supramaximal short duration intermittent exercise in neutr al and hot environmental conditions on changes in plasma volume. The r eturn of plasma volume (PV) to pre-exercise values following different recovery conditions was also examined. Methods. Experimental design. Within subject design in which one way analysis of variance was conduc ted. Setting. Research, sports science academic institute. Participant s. Ten trained men, 25.5+/-3/1 (yrs), volunteers. Interventions. Subje cts performed six 1-min bouts of exercise at 100% (V) over dotO(2)peak on a cycle ergometer, with 4-min rest intervals between the bouts. Ea ch subject exercised twice in thermoneutral (22 degrees C, 40% RH) and twice in hot (35 degrees C, 30% RH) conditions. Exercise was followed by either 40 min of passive recovery (sitting) or by 20 min active re covery (cycling at 35 % (V) over dotO(2)peak) and 20 min passive recov ery, named thereafter ''active recovery''. Measures. Hematocrit (Hct) and hemoglobin (Hb) were determined upon entry into the climatic chamb er following 20 min rest in the chamber (pre-exercise), immediately po stexercise, and 40 min postexercise. From the changes in Hct and Hb, P V changes were calculated. Results. There was a significant decrease i n PV immediately postexercise. However, there was no significant diffe rence between the two types of environmental conditions and no differe nce between the two types of recovery. PV increased significantly foll owing recovery and returned to pre-exercise values following 40 min of recovery. Conclusions. Changes in PV caused by maximal short duration cycling bouts is not affected by environmental conditions, PV returns to its pre-exercise values within 40 min of recovery regardless of th e recovery mode.