The influence of different ranges of motion testing on the isokinetic strength of the quadriceps and hamstrings

Objective: To evaluate bilateral quadriceps and hamstrings strength, at two different ranges of motion (RoM): 30 ◦ (SRoM) and 90 ◦ (FRoM), using different angular velocities. Background: Recent studies have indicated that short RoM isokinetic testing of knee muscles yielded strength findings that were compatible with those derived from a much larger RoM. However, findings were based on a single adjusted velocity in each of the RoMs. Method: Sixteen healthy male students volunteered to participate in this study. Two testing sessions, a week apart, were performed. In the first session testing started with a RoM of 90 ◦ (FRoM, 0 ◦ - full extension) and angular velocities of 60 and 180 ◦ /s. Measurements related to concentric (quadriceps and hamstring) and eccentric (quadriceps only) contractions. In the second part of the test, the RoM was adjusted to 30 ◦ (SRoM, 30-60 ◦ knee flexion) with velocities of 30 and 60 ◦ /s, respectively. The order of RoM testing was reversed in the second session. All tests were conducted bilaterally. Results: Both FRoM- and SRoM-based scores have shown good reproducibility based on the Bland Altman plots and low values of standard error of measurement and coefficient of variance of standard deviation. No statistically significant differences were noted between the FRoM and SRoM-based strength scores. The results suggest that range of motion used in isokinetic testing alone or in combination with other factors, namely side tested and isokinetic velocity, does not significantly influences changes in peak torque values for both quadriceps and hamstrings. Conclusion: This study suggests that SRoM isokinetic testing provides an effective alternative to the commonly applied range.