The hypothesis that brief intermittent exercise-induced increases in human skeletal muscle metabolic mRNA is dependent on relative workload was investigated.
Trained (n = 10) and untrained (n = 8) subjects performed exhaustive intermittent cycling exercise (4 × 4 min at 85% of V˙O2peak, interspersed by 3 min). Trained subjects also performed the intermittent exercise at the same absolute workload as the untrained subjects, corresponding to 70% of V˙O2peak (n = 6).
Exercise at 85% of V˙O2peak elevated (P < 0.001) venous plasma lactate to 10.1 ± 0.4 and 10.8 ± 0.5 mM in the trained and untrained subjects, respectively. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) mRNA expression was increased (P < 0.001) approximately four- to fivefold for several hours after exercise in both groups. After exercise at 70% of V˙O2peak, venous plasma lactate was less (P < 0.001) elevated (3.1 ± 0.7 mM) and PGC-1α mRNA content was less (P < 0.05) increased (approximately threefold) than after exercise at 85% of V˙O2peak. Likewise, pyruvate dehydrogenase kinase 4 and hexokinase II mRNA expressions were increased (P < 0.05) only after exercise performed at 85% of V˙O2peak in the trained subjects. Hypoxia-inducible factor 2α mRNA only increased (P < 0.05) 3 h into recovery in trained subjects, with no difference between the 70% and 85% of V˙O2peak trial. No change in hypoxia-inducible factor 1α, phosphofructokinase, citrate synthase, or lactate dehydrogenase, heart and muscle isoforms, mRNA expressions was detected after any of the exercise trials.
The relative intensity of brief intermittent exercise is of major importance for the exercise-induced increase of several mRNA, including PGC-1α.
1Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, DENMARK; 2Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, DENMARK; 3Rigshospitalet, Copenhagen Muscle Research Centre, Copenhagen, DENMARK; 4Centre of Inflammation and Metabolism, University of Copenhagen, Copenhagen, DENMARK; and 5Department of Biology, University of Copenhagen, Copenhagen, DENMARK
Address for correspondence: Nikolai Baastrup Nordsborg, M.Sc., Ph.D., Copenhagen Muscle Research Centre, University of Copenhagen, Department of Exercise and Sport Sciences, Universitetsparken 13, 2100 Copenhagen, Denmark; E-mail: email@example.com.
Submitted for publication July 2009.
Accepted for publication January 2010.