Gas exchange parameters, muscle blood flow and electromechanical properties of the plantar flexors

Sixteen men were tested to determine VO2max (ml X kg-1 X min-1), anaerobic threshold VO2 (ATVO2) and oxygen kinetics (time constant, T.C.) during running on a treadmill. For measuring maximal calf blood flow (maxBF, ml X 100 ml-1 X min-1), venous occlusion plethysmography was employed immediately following a combination of arterial occlusion and toe raising exercise to exhaustion. In addition, supramaximal electrical stimulations were given to determine maximal calf twitch force (Fmax, N), maximal rate of twitch force development (dF/dt) and relaxation (R X dF/dt, N X ms-1) and electro-mechanical delay time (EMD, ms). Results demonstrated that VO2max, ATVO2 and maxBF were all inversely related to T.C. (p less than 0.05). MaxBF and ATVO2 showed the highest correlation (r = 0.89, p less than 0.01). Stepwise multiple linear regression analyses revealed that variance in VO2max (60%) and ATVO2 (84%) could be accounted for by the combined effects of the following peripheral factors: VO2max = 51,25-3.24(dF/dt) + 0.14(maxBF), and ATVO2 = 11.68 + 0.42(maxBF) - 0.2(Fmax). These findings, together with the results of cluster analysis, suggest a tight link between ATVO2 and peripheral blood flow capacity. On the other hand, a moderate correlation (r = 0.64, p less than 0.01) between VO2max and maxBF might be due in part to individual differences in oxygen extraction-utilization capacity during heavy exercise above anaerobic threshold.