Reliability Of Isokinetic Knee Flexion And Extension Total Work And Unilateral Endurance Ratios

Abstract

PURPOSE: Isokinetic assessment of unilateral knee flexor and extensor functionality is often evaluated through the hamstrings-quadriceps (H:Q) strength ratio, measured in units of peak torque. Clinical use of an isokinetic unilateral H:Q endurance ratio, measured in units of total work, may provide a supplementary perspective of knee flexor and extensor functionality, yet the reliability of this measure has not yet been established. Therefore, the purpose of this study was to determine the intersession reliability of knee flexion (KF) and extension (KE) total work, and the unilateral H:Q endurance ratio. METHODS: Twenty-eight healthy young adults (14 males, 14 females) volunteered for two isokinetic (60°/s, 6 repetitions) testing sessions (48 hr apart). Dominant (DOM) and nondominant (NDOM) KF and KE testing was conducted in a random limb testing order; KE and KF total work was computed across the 6 repetitions, as well as the unilateral H:Q endurance ratio (KF ÷ KE). Following normality and heteroscedasticity exploration, relative reliability of the total work measures was assessed by interclass correlation coefficients (ICC, model: 2,1) while dependent t tests were used to evaluate systematic bias between the two testing sessions. Additionally, absolute reliability was assessed by calculating coefficients of variation (CV). RESULTS: ICCs were excellent for KF and KE of both limbs, ranging from .892 to .911, with NDOM extension being the lowest (95% confidence interval: .780-.949). The unilateral H:Q endurance ratio displayed good relative reliability for the DOM (.709) and NDOM (.719) limbs. No significant systematic biases were noted for any KF and KE total work, or unilateral H:Q endurance ratio measures (P ≥ .167) and all CVs for KF and KF were below 15%, ranging from 7.89% (DOM, KE) to 13.1% (NDOM, KF). Lastly, unilateral H:Q endurance ratios CVs for both limbs were below 10% (DOM, 9.08%; NDOM, 8.66%). CONCLUSION: These results demonstrate that DOM and NDOM KF and KE total work and unilateral H:Q endurance ratios have acceptable intersession reliability in healthy young adults. Future work will examine clinical utilization of isokinetic unilateral H:Q endurance ratios, in addition to H:Q strength ratios, to gain a more comprehensive isokinetic evaluation of patient KF and KE functionality.