Association Between Muscle Mass Quantity and Quality and Muscle Strength in Adults with Obesity

Background: This cross-sectional study aimed to verify the association between muscle quantity and quality and muscle strength in obese adults. Methods: : Lean mass (LM) and intracellular water (ICW) were obtained using bioelectrical impedance. Muscle quantity was expressed in kg for LM, while muscle quality was determined by ICW and the ratio of ICW/LM. Maximum strength was measured by the one-repetition maximum test (1RM) in bench press and leg press exercises at 45º. The score for total strength (Z-score) was given by the average of scores for each test. The statistical analysis included Spearman's correlation, whose results were expressed as correlation coefficients (r); crude and adjusted linear regression, expressed as adjusted coefficients of determination (R 2 ); Bayesian Information Criterion (BIC); and Akaike Information Criteria (AIC). Results: : Sixty-nine adults of both sexes with a mean age of 34 (± 7.1) years participated in the study. A strong positive correlation was found between the amount of LM and muscle strength (r = 0.83; p < 0.001). There was also a positive correlation between ICW and the ratio of ICW/LM, indicators of muscle quality, and muscle strength, resulting in strong (r = 0.83 p < 0.001) and moderate (r = 0.40 p < 0.001) magnitudes, respectively. Additionally, ICW had better predictive power for muscle strength (R2 adjusted = 0.98; AIC: 161.8483; BIC: 175.253). Conclusion: Muscle quantity and quality presented good predictive capacity for muscle strength. Assessing muscle quality can provide further clarification on how the muscle is able to produce strength in adults with obesity.