Reduction in range of movement can increase maximum voluntary eccentric forces for the human knee extensor muscles

Using the KinCom 500H isokinetic dynamometer the first part of this study measured the characteristics of the force velocity relationship curve for the human knee extensors between -1.57 (eccentric) and 3.67 (concentric) rads x s(-1) (-90 and 210 degrees s(1)) for both legs in 4 subjects. A significant increase in force generation was seen in eccentric activity at 0.52 rads x s(-1) (30 degrees s(-1)) but not at 1.57 rads x s(-1) (90 degrees s(-1)) compared to maximum voluntary isometric force (P < 0.005). This increase was, however, lower than would be expected from the classical force-velocity relationship. The second part of the study examined whether restricting the range of movement was able to further increase the eccentric forces. In a further 6 subjects, the eccentric contractions were repeated during either an 80 degrees (15-95 degrees flexion) and a 50 degrees (45-95 degrees flexion) range of movement. Significant increases in force were seen over the shorter range of movement at 0.52 rads x s(-1) (30 degrees s(-1)) (P = 0.006) and 1.57 rads x s(-1) (90 degrees s(-1)) (P < 0.001).