Abstract
Tracking changes in body composition may provide key information about the effectiveness of training programs for athletes. This study reports on the agreement between bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) for tracking body composition changes during a seven-week offseason training program in 29 NCAA collegiate American football players. Body composition in subjects (mean ± SD; age: 19.7 ± 1.5 y; height: 179.8 ± 6.6 cm; body mass (BM: 96.1 ± 12.6 kg; DXA body fat: 20.9 ± 4.4%) was estimated using BIA (InBody 770) and DXA (Hologic Horizon) before and after the training intervention. Repeated measures ANOVA and post hoc comparisons were performed. Longitudinal agreement between methods was also examined by concordance correlation coefficient (CCC) and Bland–Altman analysis alongside linear regression to identify bias. Significant method by time interactions were observed for BM (DXA: 1.1 ± 2.4 kg; BIA: 1.4 ± 2.5 kg; p < 0.03), arms fat-free mass (FFM) (DXA: 0.4 ± 0.5 kg; BIA: 0.2 ± 0.4 kg; p < 0.03), and legs FFM (DXA: 0.6 ± 1.1 kg; BIA: 0.1 ± 0.6 kg; p < 0.01). Post hoc comparisons indicated that DXA—but not BIA—detected increases in FFM of the arms and legs. Time main effects, but no method by time interactions, were observed for total FFM (DXA: 1.6 ± 1.9 kg; BIA: 1.2 ± 2.1 kg; p = 0.004) and trunk FFM (DXA: 0.7 ± 1.3 kg; BIA: 0.5 ± 1.0 kg; p = 0.02). Changes in total BM (CCC = 0.96), FFM (CCC = 0.49), and fat mass (CCC = 0.50) were significantly correlated between BIA and DXA. DXA and BIA may similarly track increases in whole-body FFM in American collegiate football players; however, BIA may possess less sensitivity in detecting segmental FFM increases, particularly in the appendages.
Highlights
IntroductionIn collegiate American football programs, strength and conditioning practitioners often design the initial period of offseason training to prioritize increases in fat-free mass (FFM) and muscular performance in athletes
The main objective of this study was to compare body composition changes estimated by dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) in Division III collegiate American football players during an early-offseason training program
In previous research comparing fat-free mass index (FFMI) between divisions of college football, Trexler et al [3] concluded that FFMI was capable of discriminating between Division I and Division II college football players. While this would sensibly extend to Division III due to the competitive advantage fat-free mass (FFM) may confer in football, the present study finds that the Division III players in this study had similar DXA-derived
Summary
In collegiate American football programs, strength and conditioning practitioners often design the initial period of offseason training to prioritize increases in fat-free mass (FFM) and muscular performance in athletes This period allows for recovery of FFM, as research suggests that athletes experience significant reductions in FFM over the course of a competitive season [1,2]. Improvements in football performance due to favorable FFM changes are likely related to their beneficial effects on relevant performance outcomes, such as strength and power [6,7] These variables are important in college football and can be used to differentiate players by division [4,8] and predict starters and non-starters [9]. These exercise performance outcomes are assumed to be predictive of sport performance at the professional level, contributing to an increased focus on bench press and jump performance at the National
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