Sheperd, S., Wilson, O., Bradley, J., Clark, J., Cocks, M., Thogersen-Ntoumani, C., Taylor, A., Anton, W., & Shaw, C. (2013). Group-based high intensity interval training improves adherence and reduces cardio-metabolic risk factors in sedentary individuals. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 2160.

This study investigated the hypothesis that a 10-week instructor-led group-based high-intensity interval training intervention would enhance exercise capacity and improve cardio-metabolic risk factors in previously sedentary individuals to a similar extent as traditional endurance training. Overweight sedentary volunteers (M = 22; F = 37) were randomly assigned to undertake high-intensity interval training or traditional endurance training exercise classes. High-intensity interval training consisted of repeated sprints (15-60 seconds duration) on a spin ergometer interspersed with periods of recovery cycling (<25 minutes per session, three times per week). Traditional endurance training Ss cycled at a constant workload (~65% VO2max) on a spin ergometer (30-45 minutes per session, five times per week). Assessments of VO2max, body composition (bioimpedance), insulin sensitivity (oral glucose tolerance test), and blood lipid profiles were made pre- and post-training.

Mean weekly training-time was 65±2 minutes for the high-intensity interval training group and 180±10 minutes for the traditional endurance training group. Adherence was greater in the high-intensity interval training group than in the endurance-training group. Training induced small decreases in weight and relative fat mass in both groups. VO2max increased in both groups. Fasting insulin concentrations were reduced and insulin sensitivity improved in both groups post-training. Fasting serum concentrations of free fatty acids increased in both groups but significantly more in the high-intensity interval training group. Total cholesterol and triglycerides were reduced in response to training in both groups. No differences between groups were detected for any of the other variables considered.

Implication. High-intensity interval training performed in an instructor-led, group environment provides a viable training mode to improve exercise capacity, insulin sensitivity, and lower blood lipids in sedentary adults. The physiological adaptations were mostly similar to those of traditional aerobic exercising but were achieved in approximately one-third of the time. High-intensity interval training is an effective time-saving exercise mode for improving the exercise-related health status of sedentary adults.

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