Short-term intensified cycle training alters acute and chronic responses of PGC1-alpha and Cytochrome C oxidase IV to exercise in human skeletal muscle

Reduced activation of exercise responsive signalling pathways have been reported in response to acute exercise after training; however little is known about the adaptive responses of the mitochondria. Accordingly, we investigated changes in mitochondrial gene expression and protein abundance in response to the same acute exercise before and after 10-d of intensive cycle training. Nine untrained, healthy participants (mean+/-SD; VO(2peak) 44.1+/-17.6 ml/kg/min) performed a 60 min bout of cycling exercise at 164+/-18 W (72 of pre-training VO(2peak)). Muscle biopsies were obtained from the vastus lateralis muscle at rest, immediately and 3 h after exercise. The participants then underwent 10-d of cycle training which included four high-intensity interval training sessions (6x5 min; 90-100 VO(2peak)) and six prolonged moderate-intensity sessions (45-90 min; 75 VO(2peak)). Participants repeated the pre-training exercise trial at the same absolute work load (64 of pre-training VO(2peak)). Muscle PGC1-alpha mRNA expression was attenuated as it increased by 11- and 4- fold (P