Lockie, RG, Carlock, BN, Ruvalcaba, TJ, Dulla, JM, Orr, RM, Dawes, JJ, and McGuire, MB. Skeletal muscle mass and fat mass relationships with physical fitness test performance in law enforcement recruits before academy. J Strength Cond Res 35(5): 1287-1295, 2021-The purpose of this study was to analyze relationships between skeletal muscle mass percentage (SMM%) and fat mass percentage (FM%) relative to fitness test performance in law enforcement recruits. Retrospective analysis was conducted on 338 recruits (271 men and 67 women) from 4 academy classes. Skeletal muscle mass percentage and FM% were measured using cost-effective and practical bioelectrical impedance analysis (BIA) equipment that used hand and foot placement. The fitness tests included grip strength; vertical jump; 75-yard pursuit run; 2-kg medicine ball throw (MBT); push-ups and sit-ups completed in 60 seconds; and the 20-m multistage fitness test. Partial correlations controlling for sex-derived relationships between SMM%, FM%, and the tests. Recruits were split into quartile groups for SMM% and FM% (group 1 had the lowest SMM% or highest FM% and group 4 the highest SMM% or lowest FM%). A 1-way multivariate analysis of variance (MANOVA), with sex as a covariate and Bonferroni post-hoc, compared between-group results. Skeletal muscle mass percentage correlated with all fitness tests expect for MBT; FM% with all but grip strength and MBT (r = ±0.107-0.293). Greater SMM% or lesser FM% tended to relate to better fitness test performance. The MANOVA data indicated groups 3 and 4 (better SMM% or FM% profiles) exhibited superior fitness than group 1 (poorest SMM% or FM% profile) (p ≤ 0.048). Recruits should ideally increase SMM% and decrease FM% before academy to optimize fitness training and testing performance, although specific guidelines should be agency specific. Staff could use BIA to monitor body composition during academy to indicate how recruits are tolerating training.
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