Effectiveness of sub-maximal intermittent exercise on muscle glycogen depletion, PGC-1 α and PDK-4 gene expression

Abstract

Several metabolic gene expressions are regulated in concert with muscle glycogen status. We hypothesized that intermittent exercise performed at high but sub-maximal intensities with long recovery periods would induce a low glycogen state that would stimul- ate peroxisome proliferator-activated receptor-γ coa- ctivator-1α (PGC1-α) and pyruvate dehydrogenase kinase-4 (PDK-4) gene expression in muscle. Nine young human subjects performed two intermittent exercise sessions. One session consisted of 60 s cycling bouts at VO2max (IE100%), and the other session consisted of 75 s cycling bouts at 80% VO2max (IE80%). Twelve bouts of exercise were completed in both sessions with a 4 min rest between each bout. Muscle specimens were obtained at pre-exercise and immediately, 1.5 h and 3 h post-exercise. Muscle gly- cogen was significantly decreased after both sessions (IE100%, 94.1 ± 5.8 to 38.7 ± 5.5 mmol/kg w.w.; IE80%, 94.6 ± 9.1 to 53.3 ± 4.8 mmol/kg w.w.; both P α and PDK- 4 mRNA expression were significantly increased after exercise in both IE100% and IE80% (PGC-1α: ~3.7 and ~2.9-fold, respectively; PDK-4: ~11.1 and ~3.5-fold, respectively; all P 100% than in IE80% (P a and PDK-4 mRNA expression, suggesting that increasing exercise intensity contributes to muscle glycogen depletion and PDK-4 mRNA expression in human skeletal muscle.