The influence of a crossfit exercise intervention on glucose control in overweight and obese adults

Abstract

Background: The American College of Sports Medicine physical activity guidelines call for 150 minutes of moderate or 75 minutes of vigorous aerobic exercise plus two days of resistance training (A-RT) per week for health benefits. Yet, most adults do not achieve the recommended amount of physical activity per week frequently citing lack of time as a barrier. High-intensity exercise protocols have improved glucose control, insulin sensitivity, fitness, and body composition, in less total time than lower intensity protocols, but have been studied as singular modes of exercise. CrossFit (CF) temporally combines A-RT together utilizing constantly varied multi-joint, full range-of-motion movements in substantially less training time than lower-intensity protocols. The aim of this study was to compare the effects of CF versus A-RT on glucose control in overweight/obese, physically inactive individuals. Methods: Eighteen overweight/obese (BMI 30.3 ± 2.8) adults (28.5 ± 5.9 years) were randomized to one of two groups: CF (3 days/week for 60 minute sessions) or A-RT (3 days/week of aerobic exercise for 50 minutes, plus ~20 minutes resistance exercise on 2 of those days) over 8-weeks. Fasting plasma glucose and 1-hour oral glucose tolerance tests were taken at baseline and post-training along with Eurofit fitness measures, VO2 peak, and body composition via dual energy X-ray absorptiometry. Results: Glucose control and body composition did not change significantly within or between groups. Both groups significantly improved muscular endurance (pushups completed on knees, CF+39.5%, p < 0.05; A-RT+24.4%, p = 0.01). The CF group improved on number of situps (CF+6.8%, p = 0.01) and VO2 peak (CF+9.1%, p < 0.05). Time spent exercising was significantly different between groups with the CF group averaging 38.7 ± 15.6 minutes per week and 13.1 ± 0.9 minutes per workout, and the A-RT group averaging 190.0 ± 10.7 minutes per week and 63.3 ± 3.6 minutes per workout. Conclusion: Eight weeks of A-RT or CF did not produce significant changes in glucose control or body composition in overweight/obese adults. However, despite exercising significantly less time per week CF training demonstrated greater improvements in fitness measures than A-RT.