The Effect of Hip Joint Angle on Isometric Midthigh Pull Kinetics

The aim of this study were to compare isometric midthigh pull (IMTP) peak force (PF), time-specific force values (100-, 150-, and 200 ms), rate of force development (RFD) at predetermined time bands (0-100, 0-150, and 0-200 ms) and net forces between 2 commonly adopted hip joint angles (145°hip145 and 175°hip175) with a 145° standardized knee angle. Twenty-eight collegiate athletes (age: 21.7 ± 1.5 years, height: 1.75 ± 0.08 m, mass: 81.5 ± 8.4 kg) performed 2 IMTP trials at each hip joint angle in a randomized counterbalanced order. A subgroup (n = 10) performed the IMTP testing 7 days later to establish the between-session reliability. Intraclass correlation coefficients (ICCs) and coefficient of variation (CV) demonstrated high within-session reliability and acceptable variability for all IMTP kinetics at each posture (ICC ≥ 0.86, CV ≤ 13.7%), excluding hip175 RFD 0-100 ms and net force at 100 ms which demonstrated greater variability (CV = 18.1-18.5%). High between-session reliability and acceptable variability were observed for all IMTP kinetics at each posture (ICC = 0.72-0.97, CV = 4.5-12.8%), excluding RFD 0-100 ms which demonstrated greater variability for both postures. Hip145 produced significantly greater time-specific force values (p ≤ 0.025, g = 0.25-0.28), RFD at predetermined time bands (p ≤ 0.001, g = 0.59-0.78), and net forces (p ≤ 0.001, g = 0.57-0.74) compared with hip175. Trivial nonsignificant differences were demonstrated between postures for PF and force at 100 ms (p > 0.05, g ≤ 0.14). Significantly greater body weights (weighing period force) were observed with hip175 compared with hip145 (p < 0.001, g = 0.74). Coaches should consider administering a hip145 for IMTP testing as greater IMTP kinetics and lower levels of pretension during the weighing period are achieved with this posture.