The acute and chronic influence of exercise on mitochondrial dynamics in skeletal muscle

Exercise and nutritional modulation are potent stimuli for eliciting increases in mitochondrial mass and function. Collectively, these beneficial adaptations are increasingly recognized to coincide with improvements in skeletal muscle health. Mitochondrial dynamics of fission and fusion are increasingly implicated as having a central role in mediating aspects of key organelle adaptations that are seen with exercise. Exercise-induced mitochondrial adaptation dynamics that have been implicated are 1) increases to mitochondrial turnover, resulting from elevated rates of mitochondrial synthesis (biogenesis) and degradative (mitophagy) processes and 2) morphological changes to the three-dimensional (3-D) tubular network, known as the mitochondrial reticulum, that mitochondria form in skeletal muscle. Notably, mitochondrial fission has also been implicated in coordinating increases in mitophagy, following acute exercise. Furthermore, increased fusion following exercise training promotes increased connectivity of the mitochondrial reticulum and is associated with improved metabolism and mitochondrial function. However, the molecular basis and fashion in which exercise infers beneficial mitochondrial adaptations through mitochondrial dynamics remains to be fully elucidated. This review attempts to highlight recent developments investigating the effects of exercise on mitochondrial dynamics, while attempting to offer a perspective of the methodological refinements and potential variables, such as substrate/glycogen availability, which should be considered going forward.