Feasibility of the two-point method for assessing the force-velocity relationship during lower-body and upper-body isokinetic tests

This study aimed to (1) evaluate the shape of the force-velocity (F-V) relationship obtained from different muscles, (2) explore the concurrent validity of the two-point method with respect to the multiple-point method, (3) evaluate whether the F-V relationship can discriminate between muscle groups and genders, and (4) explore the generalisability of the same F-V relationship parameters (maximal force [F-0], maximal velocity [V-0]), and maximal power [P-0]) between different tasks. The F-V relationship of 22 physically active participants (12 women) were tested during knee extension, knee flexion, elbow extension and elbow flexion through the multiple- (eight velocities: 30-60-90-120-150-180-210-240o/s) and two-point (two velocities: 60-180o/s) methods. The findings revealed (1) highly linear F-V relationships (r >= 0.893), (2) high concurrent validity of the two-point method for F-0, but lower for V-0 and P-0, (3) the outcomes of both methods were sensitive to the muscle groups (higher for knee muscles) and gender (higher for men), and (4) the magnitude of the same F-V parameters were poorly correlated between different tasks (median r < 0.1). These results support the two-point method as a valid and sensitive procedure for determining the maximal capacities of the muscles to produce F, but not V, during isokinetic tests.