Effect of preload and range of motion on isokinetic torque in women

The purposes of this study were to compare the effects of two preload settings (0 N, 75 N) and two ranges of motion (5-90 degrees ROM, 25-70 degrees ROM) on torque output of the knee musculature. Twenty females were randomly assessed for isokinetic concentric (CON) and eccentric (ECC) torque of the knee extensor (EXT) and flexor (FLEX) musculature at a velocity of 1.62 rads.s-1. Two four-way ANOVAs (muscle x mode x range of motion x preload) revealed significant differences in average torque between the preload and range of motion conditions (CONEXT: 5-90 degrees ROM, 75 N = 74.3 +/- 17.2 Nm; 5-90 degrees ROM, 0 N = 68.3 +/- 17.2 Nm; 25-70 degrees ROM, 75 N = 79.0 +/- 13.0 Nm; 25-70 degrees ROM, 0 N = 71.5 +/- 20.8 Nm) (ECCEXT: 5-90 degrees ROM, 75 N = 85.6 +/- 28.6 Nm; 5-90 degrees ROM, 0 N = 82.8 +/- 27.8 Nm; 25-70 degrees ROM, 75 N = 97.7 +/- 23.4 Nm; 25-70 degrees ROM, 0 N = 93.6 +/- 26.5 Nm) (CONFLEX: 5-90 degrees ROM, 75 N = 43.5 +/- 9.2 Nm; 5-90 degrees ROM, 0 N = 43.1 +/- 5.6 Nm; 25-70 degrees ROM, 75 N = 44.2 +/- 8.9 Nm; 25-70 degrees ROM, 0 N = 41.2 +/- 8.9 Nm) (ECCFLEX: 5-90 degrees ROM, 75 N = 56.7 +/- 16.3 Nm; 5-90 degrees ROM, 0 N = 55.6 +/- 17.8 Nm; 25-70 degrees ROM, 75 N = 57.3 +/- 14.0 Nm; 25-70 degrees ROM, 0 N = 51.8 +/- 14.0 Nm) (P < 0.05). No differences in peak torque values were observed. Based on the findings of this study, preload and range of motion should remain constant between and among subjects if average torque is used as a criterion measure.