Objective: The aim of this study was to establish reference values for rate of torque development (RTD) and muscle torque steadiness (MTS) of knee extensors across the lifespan, and evaluate if these measures are independently associated with Osteoarthritis Research Society International (OARSI)-recommended performance-based measures (6-minute walk test, 30-second chair stand test, stair climb test) and other clinical variables.
Methods: In this cross-sectional observational study, knee extensor strength of 764 participants (12-89 years) from the 1000 Norms Project was assessed via fixed dynamometry. Age- and sex-stratified normative RTD (Nms-1 kg-1) and MTS (Nm kg-1) values were presented as means and 95% confidence intervals. Correlations and multiple regression analyses were calculated to identify factors (age, sex, height, weight, OARSI-recommended performance-based measures, Knee Injury and Osteoarthritis Outcome Score, vertical jump, long jump, grip strength, basic gait-related knee biomechanics) independently associated with RTD or MTS.
Results: Age- and sex-stratified normative RTD and MTS reference values were generated. Male subjects exhibited higher RTD but poorer MTS (less steady) than female subjects across all age groups. Better performance in OARSI-recommended performance-based measures, vertical jump, long jump, and grip strength were associated with greater RTD but poorer MTS. Thirty-second chair stand test, stair climb test, vertical jump, long jump, and grip strength were independent determinants of RTD and MTS.
Conclusions: The RTD and MTS demonstrated associations with clinical variables relevant to knee osteoarthritis. The normative reference values generated may help identify the presence and extent of impairments in RTD and MTS associated with knee osteoarthritis and assist in developing responsive outcome measures for therapeutic trials.
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