1. Jason L. Talanian1,
2. Stuart D. R. Galloway2,
3. George J. F. Heigenhauser3,
4. Arend Bonen1, and
5. Lawrence L. Spriet1

Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada, Department of Sport Studies, University of Stirling, Stirling, Scotland; and Department of Medicine, McMaster University, Hamilton, Ontario, Canada Address for reprint requests and other correspondence: J. L. Talanian, Dept. of Human Health and Nutritional Sciences, Univ. of Guelph, Guelph, ON, Canada N1G 2W1 (e-mail: jtalania@uoguelph.ca)

Abstract

Our aim was to examine the effects of seven high-intensity aerobic interval training (HIIT) sessions over 2 wk on skeletal muscle fuel content, mitochondrial enzyme activities, fatty acid transport proteins, peak O₂ consumption (V̇O_{2 peak}), and whole body metabolic, hormonal, and cardiovascular responses to exercise. Eight women (22.1 ± 0.2 yr old, 65.0 ± 2.2 kg body wt, 2.36 ± 0.24 l/min V̇O_{2 peak}) performed a V̇O_{2 peak} test and a 60-min cycling trial at ∼60% V̇O_{2 peak} before and after training. Each session consisted of ten 4-min bouts at ∼90% V̇O_{2 peak}with 2 min of rest between intervals. Training increased V̇O_{2 peak} by 13%. After HIIT, plasma epinephrine and heart rate were lower during the final 30 min of the 60-min cycling trial at ∼60% pretraining V̇O_{2 peak}. Exercise whole body fat oxidation increased by 36% (from 15.0 ± 2.4 to 20.4 ± 2.5 g) after HIIT. Resting muscle glycogen and triacylglycerol contents were unaffected by HIIT, but net glycogen use was reduced during the posttraining 60-min cycling trial. HIIT significantly increased muscle mitochondrial β-hydroxyacyl-CoA dehydrogenase (15.44 ± 1.57 and 20.35 ± 1.40 mmol·min⁻¹·kg wet mass⁻¹ before and after training, respectively) and citrate synthase (24.45 ± 1.89 and 29.31 ± 1.64 mmol·min⁻¹·kg wet mass⁻¹ before and after training, respectively) maximal activities by 32% and 20%, while cytoplasmic hormone-sensitive lipase protein content was not significantly increased. Total muscle plasma membrane fatty acid-binding protein content increased significantly (25%), whereas fatty acid translocase/CD36 content was unaffected after HIIT. In summary, seven sessions of HIIT over 2 wk induced marked increases in whole body and skeletal muscle capacity for fatty acid oxidation during exercise in moderately active women.