Does Thigh Girth Predict Knee Extension Isometric And Isokinetic Peak Torque?

PURPOSE: The purpose of this study was to determine if thigh girth was an independent predictor of isometric and isokinetic peak torque. A secondary purpose was to determine the ideal location of thigh girth measurement. METHODS:54 male Division I football athletes, 19.67 years old (±1.40), performed Biodex dynamometer isometric strength testing at 90° knee flexion and isokinetic strength testing at 60°/sec, 180°/sec, and 240°/sec. Peak torque knee extension (ft./lb) per percent body weight was recorded. Thigh circumference was measured (cm) at 5 cm and 10 cm, superior to the patellar base and at 1/3 the length of the femur. Statistical analysis involved linear regressions to evaluate the relationship between thigh circumference and performance outcomes. A secondary analysis of individual Chi-Square Automatic Interaction Detections (CHAID) was utilized to identify distinct sets of significant predictors for various subgroups or levels of data. RESULTS: Multilinear regressions determined that a positive autocorrection existed between independent variables and was unsuitable for analysis. CHAID analysis found that thigh girth measurements at 10 cm were significant predictors of isometric peak torque (p = .001, r2 = .40), isokinetic peak torque at 60°/sec (p = .001, r2 = .45), and isokinetic peak torque at 180°/sec (p = .001, r2 = .36). For each CHAID model, performance subgrouping for thigh girth was created (Figure 1.). CONCLUSIONS: Thigh girth measurements at 10 cm superior to the patellar base can accurately predict isometric and isokinetic knee extension peak torque with moderate effect sizes in healthy Division I football players. However, thigh girth is not a linear predictor of knee extension peak torque. Varying thigh girths produce different peak torque values. The findings of this study may assist clinicians in standardizing measurements of thigh circumference and estimating expected peak torque when isometric and isokinetic testing is unavailable.