Relationships between maximal muscle oxidative capacity and blood lactate removal after supramaximal exercise and fatigue indexes in humans

International audience ; The present study in- vestigated whether blood lactate removal after supramaximal exercise and fatigue indexes measured during continuous and intermittent supramaximal exercises are related to the maximal muscle oxidative capacity in humans with different training status. Lactate recovery curves were obtained after a 1-min all-out exercise. A biexponential time function was then used to determine the velocity constant of the slow phase ('Y2), which denoted the blood lactate removal ability. Fatigue indexes were calculated during all-out (FIAO) and repeated 10-s cycling sprints (FISprint). Biopsies were taken from the vastus lateralis muscle, and maximal ADP-stimulated mitochondrial respira- tion (Vmax) was evaluated in an oxygraph cell on saponin-permeabi- lized muscle fibers with pyruvate + malate and glutamate + malate as substrates. Significant relationships were found between 'Y2 and pyru- vate + malate Vmax (r = 0.60, P < 0.05), 'Y2 and glutamate + malate Vmax (r = 0.66, P < 0.01), and 'Y2 and citrate synthase activity (r = 0.76, P < 0.01). In addition, 'Y2, glutamate + malate Vmax, and pyruvate + malate Vmax were related to FIAO ('Y2 - FIAO: r = 0.85; P < 0.01; glutamate + malate Vmax - FIAO: r = 0.70, P < 0.01; and pyruvate + malate Vmax - FIAO: r = 0.63, P < 0.01) and FISprint ('Y2 - FISprint: r = 0.74, P < 0.01; glutamate + malate Vmax - FISprint: r = 0.64, P < 0.01; and pyruvate + malate Vmax - FISprint: r = 0.46, P < 0.01). In conclusion, these results suggested that the maximal muscle oxidative capacity was related to blood lactate removal ability after a 1-min all-out test. Moreover, maximal muscle oxidative capacity and blood lactate removal ability were associated with the delay in the fatigue observed during continuous and inter- mittent supramaximal exercises in well-trained subjects.