Figure 2.

Exercise and disuse effects on mitochondrial quality and quantity. Exercise training promotes cytoprotective effects by the induction of PGC1-α protein, considered the master regulator of mitochondrial biogenesis. Exercise improves quality in two ways. First, mitochondrial dynamics are shifted such that fusion is greater than fission resulting in larger mitochondrial network. Second, increased selective mitophagy removes old and dysfunctional mitochondria (denoted with red and orange organelles). In contrast, disuse decreases PGC1-α, removing its inhibition of protein degradation pathways. Furthermore, mitochondrial dynamics are shifted toward fission causing a small, fragmented, and dysfunctional mitochondria.