Influence of blood flow occlusion on muscle oxygenation characteristics and the parameters of the power-duration relationship

It was previously (Monod H, Scherrer J. Ergonomics 8: 329-338, 1965) postulated that blood flow occlusion during exercise would reduce critical power (CP) to 0 Watts (W), while not altering the curvature constant (W'). We empirically assessed the influence of blood flow occlusion on CP, W', and muscle oxygenation characteristics. Ten healthy men (age: 24.8 +/- 2.6 yr; height: 180 +/- 5 cm; weight: 84.6 +/- 10.1 kg) completed four constant-power handgrip exercise tests during both control blood flow (control) and blood flow occlusion (occlusion) for the determination of the power-duration relationship. Occlusion CP (-0.7 +/- 0.4 W) was significantly (P < 0.001) lower than control CP (4.1 +/- 0.7 W) and significantly (P < 0.001) lower than 0 W. Occlusion W' (808 +/- 155 J) was significantly (P < 0.001) different from control W' (558 +/- 129 J), and all 10 subjects demonstrated an increased occlusion W' with a mean increase of similar to 49%. The present findings support the aerobic nature of CP. The findings also demonstrate that the amount of work that can be performed above CP is constant for a given condition, but can vary across conditions. Moreover, this amount of work that can be performed above CP does not appear to be the determinant of W', but rather a consequence of the depletion of intramuscular energy stores and/or the accumulation of fatigue-inducing metabolites, which limit exercise tolerance and determine W'.