Muscle strength characteristics and the predictive value of handgrip strength in young obese males: A multi‑joint isokinetic and LASSO regression analysis

Obesity is a primary global public health concern, often associated with impaired muscle function and an increased risk of exercise-related injuries. This cross-sectional study aimed to elucidate the associations among muscular strength, body load, and functional capacity in young adults with obesity. A total of 75 male university students were recruited, including a normal-weight group (n = 47, BMI 18.5-24.99) and an obese group (n = 28, BMI ≥ 30). Assessments included handgrip strength, one-repetition maximum (1RM) for squat, deadlift, and bench press, as well as isokinetic strength evaluations across four major joints (shoulder, elbow, hip, and knee), yielding 32 strength-related variables. After normalizing all strength measures to body weight, the obese group demonstrated significantly lower relative strength across all parameters compared to the normal-weight group (P < 0.001), indicating a distinct "strength-to-load imbalance." To identify key predictors of handgrip strength while addressing potential overfitting, we employed least absolute shrinkage and selection operator (LASSO) regression with cross-validation. The final model retained five predictors: elbow flexion maximum work at 180°/s (EF180°Wmax), elbow flexion peak torque at 180°/s (EF180°Fmax), elbow extension peak torque at 60°/s (EE60°Fmax), shoulder flexion peak torque at 60°/s (SF60°Fmax), and group (obese vs. normal), together explaining 63.3% of the variance in handgrip strength (adjusted R² = 0.606), although this finding should be interpreted with caution due to the sample size and requires validation in larger cohorts. Notably, group membership remained a significant independent predictor (β = -0.23, P = 0.014), underscoring the persistent deficit in relative strength associated with obesity even after accounting for joint-specific strength. By incorporating a multidimensional assessment of strength across multiple joints, this study moves beyond the limitations of single-joint evaluations and offers theoretical support for the potential use of handgrip strength as a practical indicator of overall muscle function in obese populations. Further research with larger samples and longitudinal designs is needed to validate its utility as a screening tool. These findings have important implications for designing function-oriented, precision-based exercise interventions for obese populations.