Changes in plasma volume following intense intermittent exercise in neutral and hot environmental conditions.

BACKGROUND: The purpose of the present investigation was to examine the effect of supramaximal short duration intermittent exercise in neutral and hot environmental conditions on changes in plasma volume. The return 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 conducted. SETTING: Research, sports science academic institute. PARTICIPANTS: Ten trained men, 25.5 +/- 3/1 (yrs), volunteers. INTERVENTIONS: Subjects performed six 1-min bouts of exercise at 100% VO2peak on a cycle ergometer, with 4-min rest intervals between the bouts. Each 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 recovery (cycling at 35% VO2peak) and 20 min passive recovery, named thereafter "active recovery". MEASURES: Hematocrit (Hct) and hemoglobin (Hb) were determined upon entry into the climatic chamber following 20 min rest in the chamber (pre-exercise), immediately postexercise, and 40 min postexercise. From the changes in Hct and Hb, PV changes were calculated. RESULTS: There was a significant decrease in PV immediately postexercise. However, there was no significant difference between the two types of environmental conditions and no difference between the two types of recovery. PV increased significantly following 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 the recovery mode.

Physiological and cognitive responses to cold exposure in 11-12-year-old boys.

This study investigated the effects of cold and exercise in the cold on the physiological and cognitive responses of 11-12-year-old boys. Children were dressed in sweat suits and exposed to cold (CD, 7°C), cool (CL, 13°C), and neutral (N, 22°C) environments for 110 minutes, with 10 minutes of light exercise (1 watt · kg body wt-1 ) midway through the exposure. A 30-minute "recovery" in neutral conditions followed each session. Session order was randomized. Rectal temperature (Tre) decreased significantly more in CD compared to CL and N, and continued to decrease during the recovery period. Chest skin temperature (Tch) was significantly different between conditions and remained stable even in CD, despite the decrease in Tre. Tch returned to prechamber values during the recovery period. Hand temperature (Th) decreased during CL and CL, and remained significantly lower than prechamber values following the recovery. Exercise heart rate was lower in the CD and CL(115 ± 13 and 119 ± 20 beats · min-1 ) compared to N (130 ± 17 beats · min-1 ). No differences were observed in oxygen consumption between sessions. No differences were also observed between sessions in cognitive performance on language and math tests. It was concluded that while the study conditions did not appear to affect cognitive capacity in boys, they proved sufficient to disturb core temperature. This disturbance was not corrected 30 minutes following cold exposure. Am. J. Hum. Biol. 9:39-49 © 1997 Wiley-Liss, Inc.

Blood lactate concentration following exercise: effects of heat exposure and of active recovery in heat-acclimatized subjects.

The purpose of this study was to examine the effect of ambient heat on the decrease in blood lactate concentration ([LA]bl) during passive and during active recovery. Ten trained men performed six 1-min bouts of exercise at 100% VO2peak on a cycle ergometer, with 1-min rest between the bouts. Each subject exercised twice in thermoneutral (22 degrees C, 40% RH, TN), and twice in hot (35 degrees C, 30% RH, H) conditions. Exercise was followed by either 40 min of passive recovery (sitting) or by 20 min active recovery (cycling at 35% VO2peak) and 20 min passive recovery, named thereafter, 'active recovery'. Capillary blood lactate was measured before, 1 min after, and every 5 min during recovery. Heart rate (HR), rectal and skin temperatures (Tre, Tsk) were monitored continuously. VO2 was measured prior to exercise, during the last exercise bout, the first 10 min of recovery, and periodically thereafter. Post-exercise [LA]bl was similar in all treatments (13.5 +/- 1.8, 13.0 +/- 1.3, 14.8 +/- 4.1, 13.3 +/- 2.6 mmol.l-1 for TN-active, TN-passive, H-active and H-passive, respectively). [LA]bl was significantly lower during active, compared to passive recovery in both, TN and H conditions. Environmental heart did not independently affect [LA]bl during passive or active recovery. Exercise resulted in an elevation in Tre in all treatments, with a significantly higher Tre during active recovery in H compared to the other sessions. Likewise, no differences in HR and in VO2 were observed between H and TN conditions during active nor during passive recovery.(ABSTRACT TRUNCATED AT 250 WORDS)