Prior arm exercise speeds the VO2 kinetics during arm exercise above the heart level

Purpose: To test the hypothesis that the initial O-2 uptake kinetics during exercise where the rise in blood flow (and, by implication, O-2 delivery) to the working muscles during an abrupt increase in exercise intensity is reduced (i.e., arm exercise performed above the level of the heart) would be faster when preceded by a bout of high-intensity exercise. Methods: Eleven physically active males completed two protocols, each consisting of two consecutive bouts of 6 min of high-intensity arm crank exercise separated by 6 min of recovery. In one protocol, the arm crank exercise was performed with the arms below the level of the heart (< HL); in the other, the arms were above the level of the heart (> HL). Results: In the < HL protocol, the VO2 fast component time constant was not significantly affected by prior exercise (35.9 +/- 8.7 and 35.5 +/- 8.9 s in bouts 1 and 2, respectively). The amplitudes of the VO2 fast and slow component were respectively significantly higher and significantly lower in the second bout. In the > HL protocol, the amplitudes of the VO2 fast and slow component were unaffected by prior exercise, whereas the VO2 fast component time constant was significantly reduced in the second bout (49.8 +/- 22.1 vs 40.7 +/- 13.2 s; P < 0.05). Conclusion: The results of this study demonstrate that prior high-intensity exercise caused a significant speeding of the VO2 fast component response during subsequent high-intensity arm crank exercise performed above, and not below, the level of the heart.