The Relationship Between Joint Loading Patterns And Physical Activity In Middle-Aged Adults With Obesity: A Body Composition Approach

https://doi.org/10.5281/zenodo.18316813

Abstract

Background: Obesity contributes to increased mechanical stress on the knee joint and elevates cardiometabolic risk. Physical activity and body composition are key factors influencing knee joint loading, yet large-scale evidence from Pakistan is scarce. Objective: To investigate the relationship between knee joint loading patterns and moderate-to-vigorous physical activity (MVPA) in middle-aged adults with obesity, and to evaluate the mediating roles of fat mass and lean mass. Methods: A cross-sectional study included 500 adults (260 males, 240 females; age 25–40 years) with obesity from urban Pakistan. Knee joint loading was measured using force plates and gait analysis. Physical activity was assessed with accelerometers. Body composition was determined via DXA scans, including fat and lean mass. Muscle strength and cardiometabolic variables (blood pressure, CRP, lipids, HOMA-IR) were recorded. Statistical analyses included descriptive statistics, Pearson correlations, multiple regression, mediation analysis and joint loading parameters. Figures included scatterplot of knee joint loading vs MVPA (Figure 1), mediation diagram (Figure 2), and peak vertical ground reaction force by sex (Figure 3). Results: MVPA was negatively correlated with peak knee joint loading (r = −0.48, p < 0.001). Multiple regression indicated that higher MVPA (β = −0.34, p < 0.001) and lean mass (β = −0.26, p = 0.002) were associated with lower knee loading, whereas fat mass (β = 0.42, p < 0.001) increased joint stress. Mediation analysis revealed partial mediation of the MVPA–knee loading relationship via fat mass (indirect effect: −0.32, p < 0.001) and lean mass (indirect effect: −0.19, p = 0.009). Peak vertical ground reaction force was slightly higher in males than females (1.23 ± 0.15 vs. 1.19 ± 0.13 BW). Higher muscle strength was associated with lower systolic and diastolic blood pressure, CRP, triglycerides, cholesterol, and HOMA-IR, particularly in men with abdominal obesity. Joint loading parameters during walking (Table 5) indicated that mechanical stress was influenced by both body composition and activity levels. Conclusion: Higher MVPA reduces knee joint loading directly and indirectly via improvements in body composition. Lean mass mitigates, while fat mass increases mechanical stress on the knee. Incorporating physical activity and strength-based interventions may reduce joint overload and cardiometabolic risk in middle-aged Pakistani adults with obesity.