Effect of training on skeletal muscle bioenergetic system in patients with mitochondrial myopathies: A computational study.

A computer model of the skeletal muscle bioenergetic system, involving the "Pi double-threshold" mechanism of muscle fatigue, was used to investigate the effect of muscle training on system kinetic properties in mitochondrial myopathies (MM) patients with inborn OXPHOS deficiencies. An increase in OXPHOS activity and decrease in peak Pi can account for the training-induced increase in V̇O2max, acceleration of the primary phase II of the V̇O2 on-kinetics, delay of muscle fatigue and prolongation of exercise at a given work intensity encountered in experimental studies. Depending on the mutation load and work intensity, training can bring the muscle from severe- to very-heavy- to moderate-exercise-like behavior, thus lessening the exertional fatigue and lengthening the physical activity of a given intensity. Training significantly increases critical power (CP) and slightly decreases the curvature constant (W') of the power-duration relationship. Generally, a mechanism underlying the training-induced changes in the skeletal muscle bioenergetic system in MM patients is proposed.