Does Body Composition Predict Leg Tuck Performance?

The U.S. Army implemented the Army Combat Fitness Test (ACFT) to replace the previous fitness test and better assess combat readiness. The events included a three-repetition maximum deadlift, standing power throw, hand-release push-ups, sprint-drag-carry, leg tucks, and a 3.2 km run. The leg tuck (LTK) was included to assess core strength and endurance, and a Soldier’s ability to complete combat tasks, such as scaling a wall or obstacle. However, the LTK posed a challenge, leading to increased ACFT failure rates that was attributed to sexual dimorphism. While this may be the case, it is unclear how body composition contributes to LTK performance. PURPOSE: To determine the influence of body composition (lean body mass [LBM], fat mass [FM]) on LTK performance among U.S. Army Soldiers. METHODS: Thirty-four healthy, active-duty Soldiers (n = 20 male, n = 14 female; age 29.9 ± 6.8 years; LBM 53.1 ± 12.3 kg; FM 18.8 ± 7.6 kg; LTK 9.8 ± 7.6 repetitions [reps]) completed a whole-body dual energy x-ray absorptiometry (DXA) scan and maximal effort LTK trial (up to 20 reps). A multiple regression analysis examined the relationship between body composition and LTK performance. An alpha level of ≤0.05 was used to determine statistical significance. RESULTS: LTK performance was moderately correlated with LBM (r = .44, p = .008) and strongly correlated with FM (r = -.52, p = .002). The multiple regression model significantly predicted LTK performance, F(2,31) = 32.1, p < .001, indicating that body composition explained 67.5% of the variability in LTK performance. Both LBM and FM were significant independent predictors of LTK performance (β = .41, p < .001; β = -.73, p < .001, respectively). It is estimated that a 1 kg decrease in FM or 1 kg increase in LBM, increased the LTK performance by approximately 1.37 and 2.42 reps, respectively. CONCLUSIONS: FM and LBM are both correlated with LTK performance. Additionally, body composition is a significant predictor of LTK performance among healthy, active-duty Soldiers. The problematic nature of the LTK that was attributed to sex differences, may have been attenuated by manipulating training and nutritional variables focused on body composition improvement. The potential combat readiness applicability of the LTK warrants that future studies explore the utility of training on LTK performance.