Skeletal Muscle Mass Estimation Equations: A Practical Approach For Assessing Muscle And Strength Relationships.

BACKGROUND: There are various methods to measure skeletal muscle mass (SMM), but practitioners may sometimes face resource constraints, making alternative measurement approaches necessary. PURPOSE: Thus, the purpose of this study was to evaluate the relationships between different SMM measurements and maximal strength to determine the efficacy of using skeletal muscle estimation equations (SME) as a cost-effective alternative. METHODS: Twenty-two male subjects (21.5 ± 1.8 yrs; 175.5 ± 5.4 cm; 84.5 ± 16.6 kg) participated in a BodPod analysis to assess fat-free mass (FFM), and an assessment of ten sites (bilateral biceps, forearms, quadriceps, calves, neck, and waist) to compute summed muscle circumferences (SMC). SMM was estimated using an SME. Maximal strength was assessed through 1-repetition maximums (1RM) for back squat (BS), bench press (BP), deadlift (DL), and total (TOT). Isometric hand grip strength (HGS) was measured as an additional indirect assessment of strength. Pearson correlation and Hopkins effect size were used to evaluate relationships between SMM measurements and maximal strength. Alpha level was set at p ≤ 0.05. RESULTS: SME showed strong relationships with FFM (r = 0.922), SMC (r = 0.937), and 1RM BS (r = 0.595), BP (r = 0.469), DL (r = 0.614), and TOT (r = 0.597). HGS demonstrated strong relationships across all 1RM strength measurements (r = 0.557-0.693) and SME (r = 0.519). FFM and SMC similarly correlated strongly with all 1RM outcomes (r = 0.529-0.689) and HGS (r = 0.534-0.567). All correlations were significant p < 0.001, indicating strong associations across all measurements. CONCLUSIONS: SME offers an accurate estimate of SMM compared to both indirect FFM and direct SMC measurements. Furthermore, when robust SMM assessments are unavailable or frequent evaluations are not feasible, pairing 1RMs and HGS with SME provides a comprehensive understanding of true SMM.