High intensity crossfit training compared to high intensity swimming : A pre-post trial to assess the impact on body composition, muscle strength and resting energy expenditure

Objectives: The aim of this study was to evaluate the impact of two different forms of high intensity training i.e. power CrossFit and intermittent swimming, on body composition markers, max strength and resting energy expenditure. Methods: This pre-post trial was conducted on twenty three subjects (14 female, 9 male; mean age = 31.74±7.46 years; BMI = 23.665 ± 2.994 kg/m2). They were assigned into interventions of CrossFit training or swimming (CrossFit/Swimming: 10/13) for 8-weeks (60 min, 3 times per week). Using dual X-ray energy absorptiometry (DXA), we measured body mass composition markers such as body weight, total free fat mass, total fat mass, arms and legs free fat mass, and percentage of android and gynoid fat mass. Also muscle strength and resting energy expenditure were measured at baseline and immediately after 8 weeks of training intervention. Feasibility measures of recruitment and injury were also assessed. These variables were measured at baseline and after 8 weeks and compared within and between groups, using paired t-tests and linear regression models, to detect significant changes. Results: Between groups, data comparisons (pre-post intervention training) demonstrated a significant effect of CrossFit on gynoid fat (β = -1.42%; CI 95% -2.81; -0.03; P = 0.047), and suggestive but not significant variations in decreasing for total fat mass (β -1427 g, CI 95%: -2861, 7, 31; P = 0.051) and android fat (-2.64%, CI 95%: -5.36, 0.08; P = 0.056). Conclusions: This study showed the potential benefits of high intensity training in improvement of body composition markers. In particular, CrossFit is more effective than swimming in losses of total fat mass, specifically of gynoid and android fat mass. Further research is needed to understand the potential of CrossFit training on health.