Validity of the Handheld Dynamometer Compared with an Isokinetic Dynamometer in Measuring Peak Hip Extension Strength

Purpose: To determine whether the handheld dynamometer (HHD) is an appropriate tool to assess and quantify peak hip extension strength in prone standing position by (1) evaluating the concurrent validity of the HHD versus an isokinetic dynamometer (IKD), (2) establishing the minimal detectable change (MDC), and (3) determining the validity of single-trial versus multi-trial measures. Method: A convenience sample of 20 healthy adults was recruited for this cross-sectional study. Measures of peak hip extension strength were collected in prone standing position with both the HHD and the IKD and in supine position with the IKD. Results: Values of r were 0.37 for HHD versus IKD prone standing and 0.51 for HHD versus IKD supine. MDC was 14.8 Nm for the HHD, 25.6 Nm for IKD prone standing, and 41.5 Nm for IKD supine. High correlations (r values of 0.92-0.94) were observed between trial 1 and the mean of three trials. Conclusions: The HHD has moderate concurrent validity in measuring peak hip extension strength in the prone standing position in healthy adults. MDC for hip extension strength was lowest using the HHD. Single-trial values showed a high correlation with three-trial mean values.