RESUMEN
We tested the hypothesis that AMPK activation and peroxisome proliferator gamma coactivator 1 alpha (PGC-1α) expression are not augmented as exercise intensity (power output) increases from maximal to supramaximal intensities and conducted an exploratory analysis comparing AMPK activation and PGC-1α expression in males and females. Seventeen (n = 9 males; n = 8 females) recreationally active, healthy, young individuals volunteered to participate in the current study. Participants completed work matched interval exercise at 100% (Max) and 133% (Supra) of peak work rate (WRpeak). Intervals were 1 min in duration and participants were prescribed 6 and 8 intervals of Max and Supra, respectively, to equate external work across protocols. PGC-1α mRNA expression and activation of AMPK (p-ACC) were examined in muscle biopsy samples. Interval WR (watts; W), intensity (%WRpeak) and average HR (bpm), blood lactate (mmol/L) and rating of perceived exertion were all higher (all p < 0.05) in Supra. Fatigue was greater (p < 0.05) in Supra. PGC-1α mRNA expression significantly increased after exercise in Max (p < 0.01) and Supra (p < 0.01), but was not significantly different (p = 0.71) between intensities. A main effect of time (Pre - 0 h) (p < 0.01) was observed for p-ACC; however, no effect of intensity (p = 0.08) or interaction (p = 0.97) was observed. No significant effects of time (p = 0.05) intensity (p = 0.42), or interaction (p = 0.97) were observed for p-AMPK (Thr172). Exploratory sex analysis demonstrated a main effect of sex for p-ACC (greater p-ACC in males; p < 0.05) but not for p-AMPK or PGC-1α expression. Our results confirm that AMPK-PGC-1α signalling is not augmented following supramaximal exercise and provide novel data demonstrating a decrease in AMPK activation (p-ACC) in females compared to men. Trial registration: https://doi.org/10.17605/OSF.IO/U7PX9.