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Excerpt
Longitudinal assessment of lean mass is likely to benefit the competitive performance of athletes in football and other team sports requiring strength and power. PURPOSE: To assess changes in lean mass in elite rugby football union players over several years of a monitoring program. METHODS: We measured body mass and sum of seven skinfold thicknesses of 72 Super-12 rugby players on 12.3 ± 6.8 occasions (mean ± SD) during 2.0 ± 1.3 years. Repeated-measures multiple linear regression of logtransformed variables yielded a lean mass index (LMI) that tracked changes in mass controlled for changes in skinfold thickness. Similar analyses yielded the effects of phase of year (pre-season, Super-12 games, club games, off-season) and time in the program (modeled as a quadratic) on mass, skinfolds, and the LMI. Magnitudes of changes were interpreted via Cohen effect sizes. RESULTS: The LMI function was (body mass)/(sum of skinfolds) x, where × = 0.13 ± 0.04 for forwards and 0.14 ± 0.06 for backs. The LMI decreased to a small but substantial minimum after ∼2 years for forwards (mean decrease 2.2%, 90% confidence limits ± 0.7%) and backs (1.9%, ± 0.7%). These changes were superimposed on trivial fluctuations in body composition between phases, with the exception of a small decrease in skinfolds (−5.4%, ± 1.4%) for the forwards during the Super-12 phase. CONCLUSIONS: Monitoring of lean mass provided evidence of negative long-term changes in body composition that could be addressed with appropriate training and nutrition.
