Short high-intensity interval training: a time efficient exercise strategy for overweight and obese compared with regular endurance training
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Background: Aerobic training plays an important role in preventing and treating overweight and obesity. The physical activity recommendation to improve health is set to a minimum of 150 minutes of moderate intensity exercise per week. However, evidence regarding the most efficient exercise strategy for improved cardiovascular health in overweight and obese individuals is still lacking. Recent studies suggest that a number of physiological adaptations associated with traditional continuous endurance training can be induced faster and maybe to a larger degree, with a small volume of high-intensity endurance training. The study aim was to compare maximal oxygen uptake (VO2max), work economy and skeletal muscle mitochondrial content in overweight and obese subjects after short high-intensity with that obtained after regular endurance training with moderate exercise intensity. A secondary aim was to see how these two exercise-regimens affected the endurance performance. Methods: Seven males and eleven females (43±8 years, BMI 29.8±2.7, VO2max 3.14±0.64 L·min-1) were randomized to either a short high-intensity interval training group (SIT) or a moderate continuous training group (MCT). SIT consisted of 10×60 sec intervals at VO2max running velocity and inclination, separated by 60 sec of recovery. MCT consisted of 45 min treadmill running at 55-65% of VO2max. Both training protocols were performed 3 d·wk-1 for 6 wk. VO2max and work economy were measured during treadmill running and walking. Endurance performance was assessed as running time to exhaustion. Mitochondrial content was revealed by vastus lateralis muscle biopsies and citrate synthase activity. Results: No significant difference in VO2max and body mass was observed within or between the two interventions. Work economy improved significantly ~9% after SIT and MCT. Muscle mitochondrial content, assessed as activity of citrate synthase increased significantly by 34.9% and 56.1% after SIT and MCT, respectively, with no differences between the groups. Endurance performance increased significantly by 115.5% and 51.5% after SIT and MCT, respectively, with no differences between the groups. Conclusion: SIT is a time efficient exercise strategy for improving muscle mitochondrial content, work economy and endurance performance compared with MCT.