The Unsuitability of Energy Expenditure Derived From Microtechnology for Assessing Internal Load in Collision-Based Activities

This aim of this study was to examine the validity of energy expenditure derived from microtechnology when measured during a repeated-effort rugby protocol. Sixteen male rugby players completed a repeated-effort protocol comprising 3 sets of 6 collisions during which movement activity and energy expenditure (EE GPS ) were measured using microtechnology. In addition, energy expenditure was estimated from open-circuit spirometry (EE VO2 ). While related ( r = .63, 90%CI .08–.89), there was a systematic underestimation of energy expenditure during the protocol (–5.94 ± 0.67 kcal/min) for EE GPS (7.2 ± 1.0 kcal/min) compared with EE VO2 (13.2 ± 2.3 kcal/min). High-speed-running distance ( r = .50, 95%CI –.66 to .84) was related to EE VO2 , while PlayerLoad was not ( r = .37, 95%CI –.81 to .68). While metabolic power might provide a different measure of external load than other typically used microtechnology metrics (eg, high-speed running, PlayerLoad), it underestimates energy expenditure during intermittent team sports that involve collisions.