High Intensity Interval Training Rapidly Increases Skeletal Muscle Oxidative Capacity In Previously Sedentary Middle-aged Adults

Abstract

There is growing appreciation of the potential for high intensity interval training (HIT) to rapidly stimulate metabolic adaptations that resemble traditional endurance training, despite a low total exercise volume (Exerc Sports Sci Rev 36:58-63, 2008). However, much of this work has been conducted on young active individuals (≤30 yr) and the results may not be generalized to older, less active populations. In addition, many studies have employed "all out“, variable-load exercise interventions (e.g., repeated Wingate Tests) that may not be safe, practical or well tolerated by certain individuals. PURPOSE: To determine the effect of a short program of low-volume, submaximal, constant-load HIT on skeletal muscle metabolic adaptations in sedentary middle-aged individuals who may be at higher risk for inactivity-related disorders. METHODS: Inactive but otherwise healthy men (n = 3) and women (n = 4) with a mean (±SE) age, body mass index and peak oxygen uptake (VO2peak) of 45±2 yr, 27±2 kg·m2 and 30±1 ml·kg-1·min-1 took part in the study. Subjects performed 6 training sessions over 2 wk. Each session consisted of 10 × 1 min cycling at 60% of peak power elicited during a ramp VO2peak test (∼90% of maximal heart rate) with 1 min recovery between intervals. Needle muscle biopsy samples (v. lateralis) were obtained before training and ∼72 h after the final training session. RESULTS: Muscle oxidative capacity, as reflected by the maximal activity of citrate synthase, increased by 22% after training (12.9 ± 0.7 vs. 10.6 ± 0.6 mmol·kg protein-1·h-1), which is comparable to changes previously reported after 2 wk of Wingate-based HIT in young active subjects. CONCLUSIONS: A short program of low-volume, constant-load HIT is a time-efficient strategy to rapidly increase skeletal muscle oxidative capacity in previously sedentary middle-aged men and women. Supported by CIHR.