Energy expenditure of international female rugby union players during a major international tournament: a doubly labelled water study.

The purpose of this study was to quantify the total energy expenditure (TEE) of international female rugby union players. Fifteen players were assessed over 14 days throughout an international multi-game tournament, which represented two consecutive one-match microcycles. Resting metabolic rate (RMR) and TEE were assessed by indirect calorimetry and doubly labelled water, respectively. Physical activity level (PAL) was estimated (TEE:RMR). Mean RMR, TEE, and PAL were 6.60 ± 0.93 MJ·day^-1 (1578 ± 223 kcal·day^-1), 13.51 ± 2.28 MJ·day^-1 (3229 ± 545 kcal·day^-1), and 2.0 ± 0.3 AU, respectively. There was no difference in TEE (13.74 ± 2.31 (3284 ± 554 kcal·day^-1) vs. 13.92 ± 2.10 MJ·day^-1 (3327 ± 502 kcal·day^-1); p = 0.754), or PAL (2.06 ± 0.26 AU vs. 2.09 ± 0.23 AU; p = 0.735) across microcycles, despite substantial decreases in training load (total distance: -8088 m, collisions: -20 n, training duration: -252 min). After correcting for body composition, there was no difference in TEE (13.80 ± 1.74 (3298 ± 416 adj. kcal·day^-1) vs. 13.16 ± 1.97 (3145 ± 471 adj. kcal·day^-1) adj. MJ·day^-1, p = 0.190), RMR (6.49 ± 0.81 (1551 ± 194 adj. kcal·day^-1) vs. 6.73 ± 0.83 (1609 ± 198 adj. kcal·day^-1) adj. MJ·day^-1, p = 0.633) or PAL (2.15 ± 0.14 vs. 1.87 ± 0.26 AU, p = 0.090) between forwards and backs. For an injured participant (n = 1), TEE reduced by 1.7 MJ·day^-1 (-401 kcal·day^-1) from pre-injury. For participants with illness (n = 3), TEE was similar to pre-illness (+0.49 MJ·day^-1 (+117 kcal·day^-1)). The energy requirements of international female rugby players were consistent across one-match microcycles. Forwards and backs had similar adjusted energy requirements. These findings are critical to inform the dietary guidance provided to female rugby players.