Daily energy expenditure and water turnover in female netball players from the Netball Super League: A doubly labeled water observation study

To establish the criterion-assessed energy and fluid requirements of female netball players, 13 adult players from a senior Netball Super League squad were assessed over 14 days in a cross-sectional design, representing a two- and one-match microcycle, respectively. Total energy expenditure (TEE) and water turnover (WT) were measured by doubly labeled water. Resting and activity energy expenditure were measured by indirect calorimetry and Actiheart, respectively. Mean 14-day TEE was 13.46 ± 1.20 MJ day⁻¹ (95% CI, 12.63–14.39 MJ day⁻¹). Resting energy expenditure was 6.53 ± 0.60 MJ day⁻¹ (95% CI, 6.17–6.89 MJ day⁻¹). Physical activity level was 2.07 ± 0.19 arbitrary units (AU) (95% CI, 1.95–2.18 AU). Mean WT was 4.1 ± 0.9 L day⁻¹ (95% CI, 3.6–4.7 L day⁻¹). Match days led to significantly greater TEE than training (+2.85 ± 0.70 MJ day⁻¹; 95% CI, +1.00– +4.70 MJ day⁻¹; p = 0.002) and rest (+4.85 ± 0.70 MJ day⁻¹; 95% CI, +3.13–+6.56 MJ day⁻¹; p < 0.001) days. Matches led to significantly greater energy expenditure (+1.85 ± 1.27 MJ; 95% CI, +0.95–+2.76 MJ day⁻¹; p = 0.001) than court-based training sessions. There was no significant difference in TEE (+0.03 ± 0.35 MJ day⁻¹; 95% CI, −0.74–+0.80 MJ day⁻¹; p = 0.936) across weeks. Calibrated Actiheart 5 monitors underestimated TEE (−1.92 ± 1.21 MJ day⁻¹). Energy and fluid turnover were greatest on match days, followed by training and rest days, with no difference across weeks. This study provides criterion-assessed energy and fluid requirements to inform dietary guidance for female netball players.