Seasonal Changes In Total And Regional Body Composition In Collegiate Football Players By Position

PURPOSE: Position-specific differences in body composition in American football players have been established. How total and regional (trunk, arms, legs) composition changes from pre- to post-season is unknown. Thus, this study examined longitudinal changes in total and regional body composition in NCAA Division I football players (CFP) over a competitive season. METHODS: A total of 188 male CFP aged 18-23 (20.7 ± 1.6 yrs) were included in this study. Body composition was measured via dual X-ray absorptiometry (DXA) during the pre- and post-season. Participants were grouped positionally into defensive backs (DB), defensive lineman (DL), linebackers (LB), offensive linemen (OL), punters/kickers (PK), quarterbacks (QB), running backs (RB), tight ends (TE), and wide receivers (WR). Repeated-measures ANOVA assessed effects of season and position on total and regional body composition. Post hoc pairwise comparisons determined magnitude, direction, and significance of changes in each position. RESULTS: There were significant differences in all body composition metrics (p < 0.0001) by position. There were no significant changes in total or regional measures of fat mass across the competitive season. Similarly, there was no significant changes in total or regional measures of mass or bone mass (bone mineral content) from pre- to post-season. There was a significant decrease in total lean mass (LM) (kg) from pre- to post-season in DB (-1.06 ± 1.99), DL (-0.73 ± 2.75), OL (-1.66 ± 3.03), PK (-1.62 ± 2.17), RB (-1.31 ± 2.40), TE (-1.41 ± 2.52), and WR (-1.17 ± 1.58) (p < 0.05 for all). Regionally, arm LM (kg) decreased significantly in DB (-0.28 ± 0.42) (p < 0.05). In addition, leg LM (kg) decreased significantly in DB (-0.44 ± 1.00), DL (-0.46 ± 1.27), OL (-0.65 ± 1.38), PK (-0.85 ± 0.76), RB (-0.80 ± 1.02), TE (-0.65 ± 0.93) and WR (-0.61 ± 0.81) (p < 0.05). There were no significant changes in trunk LM from pre- to post-season. CONCLUSIONS: The results of this study confirm that there is a decrease in total LM over the course of a competitive season in CFP. The present study demonstrates that this loss in LM mainly comes from the leg and arm regions of the body and occurs across all positions. This information can be used by strength and nutrition staff to develop new strategies to prevent this loss of LM over the course of a season.