Energy balance dynamics during short-term high-intensity functional training

CrossFit (CF; CrossFit Inc., Washington, DC, USA) is a form of high-intensity functional training that focuses on training across the entire spectrum of physical fitness. CF has been shown to improve a number of indicators of health but little information assessing energy balance exists. The purpose of the present study was to investigate energy balance during I week of CF training. Men and women (n = 21; mean +/- SD; age, 43.5 +/- 8.4 years; body mass index, 27.8 +/- 4.9 kg.m(-2)), with >= 3 months CF experience, had body composition assessed via air displacement plethysmography before and after 1 week of CF training. Participants wore ActiHeart monitors to assess total energy expenditure (TEE), activity energy expenditure, and CF energy expenditure (CF EE). Energy intake was assessed from TEE and Delta body composition. CF EE averaged 605 +/- 219 kcal per 72 +/- 10 min session. Weekly CF EE was 2723 +/- 986 kcal. Participants were in an energy deficit (TEE: 3674 +/- 855 kcal.day(-1); energy intake: 3167 +/- 1401 kcal.day(-1)). Results of the present study indicate that CF training can account for a significant portion of daily activity energy expenditure. The weekly expenditure is within levels shown to induce clinically meaningful weight loss in overweight/obese populations.