Dissociation of Increases in PGC-1a and Its Regulators from Exercise Intensity and Muscle Activation Following Acute Exercise

Muscle activation as well as changes in peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1a) following high-intensity interval exercise (HIIE) were examined in young healthy men (n = 8; age, 21.962.2 yrs; VO2peak, 53.166.4 ml/min/kg; peak work rate, 317623.5 watts). On each of 3 visits HIIE was performed on a cycle ergometer at a target intensity of 73, 100, or 133 % of peak work rate. Muscle biopsies were taken at rest and three hours after each exercise condition. Total work was not different between conditions (,730 kJ) while average power output (73%, 237621; 100%, 323626; 133%, 384635 watts) and EMG derived muscle activation (73%, 12626605; 100%, 20896737; 133%, 302961206 total integrated EMG per interval) increased in an intensity dependent fashion. PGC-1a mRNA was elevated after all three conditions (p,0.05), with a greater increase observed following the 100 % condition (,9 fold, p,0.05) compared to both the 73 and 133 % conditions (,4 fold). When expressed relative to muscle activation, the increase in PGC-1a mRNA for the 133 % condition was less than that for the 73 and 100 % conditions (p,0.05). SIRT1 mRNA was also elevated after all three conditions (,1.4 fold, p,0.05), with no difference between conditions. These findings suggest that intensity-dependent increases in PGC-1a mRNA following submaximal exercise are largely due to increases in muscle recruitment. As well, the blunted response of PGC-1a mRNA expression following supramaximal exercise may indicate that signalling mediated activation of PGC-1a may also be blunted. We also indentify that increases in PDK4, SIRT1, and RIP140 mRNA followin