DXA-derived estimates of energy balance and its relationship with changes in body composition across a season in team sport athletes

Abstract

This study examined the relationship between dual-energy x-ray absorptiometry (DXA)-derived estimates of energy balance (EB) and changes in body composition across various seasonal phases in team sport athletes. Forty-five Australian rules footballers underwent six DXA scans across a 12-month period (off-season [OS, Week 0–13], early [PS1, Week 13–22] and late pre-season [PS2, Week 22–31] and early [IS1, Week 3–42] and late in-season [IS2, Week 42–51]). EB (kcal·day⁻¹) was estimated from changes in fat free soft tissue mass (FFSTM) and fat mass (FM) between scans according to a validated formula. An EB threshold of ± 123 kcal·day⁻¹ for >60 days demonstrated a very likely (>95% probability) change in FFSTM (>1.0 kg) and FM (>0.7 kg). There were small to almost perfect relationships between EB and changes in FM (r = 0.97, 95% CI, 0.96–0.98), FFSTM (r = −0.41, −0.92 to −0.52) and body mass (r = 0.27, 0.14–0.40). EB was lowest during PS1 compared to all other phases (range, −265 to −142 kcal·day⁻¹), with no other changes at any time. Increases in FFSTM were higher during OS compared to PS2 (1.6 ± 0.4 kg), and higher during PS1 compared to PS2, IS1, and IS2 (range, 1.6–2.1 kg). There were no changes during in-season (−0.1–0.05 kg). FM decreased only in PS1 compared to all other seasonal phases (−1.8 to −1.0 kg). Assessments of body composition can be used as a tool to estimate EB, which practically can be used to indicate athlete’s training and nutrition behaviours/practices.

Keywords:

• AFL
• training
• nutrition
• periodization
• education

Acknowledgements

The authors acknowledge the support from the football club and the commitment made by the 45 athlete’s in allowing the use of their DXA scans for this study.

Disclosure statement

No potential conflict of interest was reported by the authors.