Effect of acute plasma volume expansion on thermoregulation and exercise performance in the heat

Purpose: We investigated the effects of acute plasma volume expansion on ex ercise performance in the heat. Methods: Six moderately trained men cycled for 40 min at 64 +/- 2% peak pulmonary oxygen uptake (VO2peak) followed by an individual performance time trial, where subjects completed a set amount of work (267 +/- 15 kJ) in as little time as possible. Exercise trials wer e performed at 35 degrees C with a relative humidity of 40%. Subjects perfo rmed two exercise trials: one after 13.1 +/- 1% acute plasma volume expansi on (PVE), which was achieved by the intravenous infusion of 8 mL.kg(-1) bod y weight of Hemaccel((R)) (35 g.L-1 polygeline, 145 mmol.L-1 Na+, and 145 m mol.L-1 Cl-) and the other without prior treatment (CON). Results: Core tem perature, skin blood flow, and heart rate progressively increased (P < 0.05 ) during exercise, but no differences were observed between trials. Plasma glucose and lactate were similar at rest and during exercise, as was VO2 du ring exercise. Exercise performance was not influenced by plasma volume exp ansion (CON 17.5 +/- 0.4 min and PVE 17.1 +/- 0.2 min). Conclusion: These d ata suggest that, in moderately trained men, plasma volume expansion alone does not: enhance thermoregulatory function and exercise performance during moderate intensity exercise in the heat.