Assessment of Metabolic Response During High‐Intensity Interval Exercise and Resting Vascular and Mitochondrial Function in Recreational CrossFit Participants

Abstract

BackgroundHigh‐intensity functional training (HIFT) can play a major role in physiological adaptations to prevent cardiometabolic disease. A majority of HIFT interventions incorporate a CrossFit (CF) training methodology, in which the goal is to increase work capacity over time while using mono‐structural, body weight, and weightlifting movements.MethodsWe measured aerobic capacity, metabolic response during high‐intensity interval exercise (HIIE), resting mitochondrial oxidative capacity, and resting large vessel function and microvascular reactivity in adults who have participated in a CF exercise for greater than one year vs. a sedentary group completing <2 h·wk‐1 of structure exercise for at least one year (SED).Results21 healthy, non‐smoking, participants were recruited (CF n = 13 vs. SED n = 8). CF participants had 40.4% greater absolute and 33.0% relative VO2 peak (P < 0.001) and lower body composition (CF = 18.6 (3.8) vs. SED = 30.3 (8.4); P < 0.001). CF participants had lower ratings of perceived exertion (P = 0.022) with higher respiratory responses (P < 0.05) and a lower heart rate response during HIIE (P = 0.024). CF participants had higher fat and carbohydrate oxidation when expressed as absolute and body weight relative values (P < 0.013), but not when expressed relative to lean mass (P > 0.200), indicating that skeletal muscle mass is a primary driver in substrate oxidation. CF participants had greater mitochondrial oxidative capacity (CF n = 12; P = 0.014). There were no differences in large artery function, but CF participants had greater baseline arterial diameter (CF n = 12; P = 0.004) and faster reperfusion following arterial occlusion (CF n = 12; P < 0.05), suggesting some influence of exercise habits on microvascular function.ConclusionOverall, these data support the effectiveness of HIFT programs, like CF exercise, to improve fitness and weight status and metabolic, mitochondrial, and vascular function.