Assessment of Lower Limb Muscle Strength and Power Using Hand-Held and Fixed Dynamometry: A Reliability and Validity Study

TLDR

Hand‑held dynamometry has not previously been used to assess isometric muscle power, and there is no consensus on the optimal method for calculating rate of force development. The study aims to evaluate the reliability of various RFD calculation algorithms, the intra‑, inter‑rater, and inter‑device reliability of hand‑held dynamometry, and its concurrent validity for measuring isometric lower‑limb strength and power, and to suggest future research in clinical populations. Isometric strength and power were measured with two hand‑held dynamometers and a KinCom reference device, and statistical analyses (ICC, Pearson, concordance, SEM, MDC) compared RFD calculation algorithms, showing that a peak 200‑ms moving‑window method yielded the best reliability. Hand‑held dynamometry demonstrated good to excellent intra‑, inter‑, and device reliability and moderate to excellent concurrent validity for hip and knee strength and power, though ankle measures were less reliable, and freely available software was provided to extract these variables.

Abstract

Hand-held dynamometry (HHD) has never previously been used to examine isometric muscle power. Rate of force development (RFD) is often used for muscle power assessment, however no consensus currently exists on the most appropriate method of calculation. The aim of this study was to examine the reliability of different algorithms for RFD calculation and to examine the intra-rater, inter-rater, and inter-device reliability of HHD as well as the concurrent validity of HHD for the assessment of isometric lower limb muscle strength and power.30 healthy young adults (age: 23±5 yrs, male: 15) were assessed on two sessions. Isometric muscle strength and power were measured using peak force and RFD respectively using two HHDs (Lafayette Model-01165 and Hoggan microFET2) and a criterion-reference KinCom dynamometer. Statistical analysis of reliability and validity comprised intraclass correlation coefficients (ICC), Pearson correlations, concordance correlations, standard error of measurement, and minimal detectable change.Comparison of RFD methods revealed that a peak 200 ms moving window algorithm provided optimal reliability results. Intra-rater, inter-rater, and inter-device reliability analysis of peak force and RFD revealed mostly good to excellent reliability (coefficients ≥ 0.70) for all muscle groups. Concurrent validity analysis showed moderate to excellent relationships between HHD and fixed dynamometry for the hip and knee (ICCs ≥ 0.70) for both peak force and RFD, with mostly poor to good results shown for the ankle muscles (ICCs = 0.31-0.79).Hand-held dynamometry has good to excellent reliability and validity for most measures of isometric lower limb strength and power in a healthy population, particularly for proximal muscle groups. To aid implementation we have created freely available software to extract these variables from data stored on the Lafayette device. Future research should examine the reliability and validity of these variables in clinical populations.