Figure 3. Effect of exercise on skeletal muscle mitochondria.

A, three daily bouts of exercise do not result in an increase in functional mitochondria in skeletal muscle as evidenced by no increase in the capacity for pyruvate oxidation. B, one bout of exercise results in an increase in PGC-1α expression measured ∼18 h after exercise. *P < 0.01, exercise versus sedentary. C, overexpression of PGC-1α in rat triceps muscle by means of electroporation resulted in downregulation of expression of phosphorylase, phosphorylase kinase and phosphofructokinase (PFK). D, knockdown of PGC-1α in C₂C₁₂ myotubes by transfection with PGC-1α shRNA results in increased expression of phosphorylase, phosphorylase kinase and phosphofructokinase. *P < 0.01, control versus empty vector (EV) or scrambled RNA (Scr). Values are means ± SEM for 6 rats per group.