A comparison of continuous and discrete testing approaches on concentric and eccentric torque production of the knee extensors

Abstract

The aim of this study was to investigate the torque produced using two commonly employed approaches to isokinetic strength testing, the continuous and discrete testing approaches, using the same dynamometer. The continuous testing approach consisted of four repetitions of maximal reciprocal concentric (Con) and eccentric (Ecc) muscle actions, with a 4-min pause after each set of repetitions to allow recovery. The discrete testing approach consisted of four maximal Con and Ecc muscle actions, each action separated by a 30-s pause. A 2-min pause followed each velocity. Both approaches were performed at velocities of 60, 120 and 1800 s -1. Each testing approach therefore encompassed the same number of maximal repetitions and the same pause time, giving equal total work and total recovery times. Full range average torque (FRAT), truncated range average torque (TRAT) and peak torque (PT) were derived from all generated torque curves. The best data (highest torque values) were utilised in subsequent analyses. Each dependent variable (FRAT, TRAT and.PT) was separately analysed using a three-way ANOVA with repeated measures on all three factors: testing approach (continuous and discrete), velocity (60, 120 and 180 0 s -1), and muscle action (Con and Ecc). A significant interaction between the independent variables testing approach and muscle action existed for all measures of strength. Contrasts revealed no difference between the Con muscle actions of the continuous and discrete testing approaches, however, the torques produced in Ecc muscle actions with the discrete testing approach were significantly greater than those produced in the continuous testing approach. Ecc torques and any derived measures incorporating Ecc torques are therefore not comparable between the testing approaches.