The Effect of Exercise Mode on Exercise‐induced Plasma Volume Expansion

Differences in hydrostatic pressure gradients between the standing and seated position indicate that treadmill exercise might promote a greater plasma volume expansion than cycle ergometer exercise. To test this hypothesis six subjects performed intermittent high intensity exercise (8 bouts of 4 min 85% of VO 2 max and 5 min 40% VO 2 max) on the treadmill and cycle ergometer. Changes in plasma volume expansion were calculated from changes in hematocrit and hemoglobin. Changes in central blood volume (CBV) were estimated from changes in trans‐thoracic impedance. CBV decreased (p<0.05) when moving from seated rest to the treadmill and remained at this reduced level throughout the exercise. CBV was unchanged when they started cycle ergometer exercise but decreased throughout the cycle ergometer exercise (p<0.05). CBV returned to control levels post exercise regardless of the exercise mode. Plasma volume expansion was similar for treadmill and cycle ergometer exercise, 9.8 ± 2.3 and 8.2 ± 2.3% (p<0.05), respectively, but strongly associated with the increase in plasma protein content (p<0.05). Initial differences in central blood volume disappeared over the course of the exercise/recovery protocol. As such, PV expansion following high intensity intermittent exercise appeared to be independent of exercise mode but highly related the increase in plasma protein content. (NIH HL 039818)