Quadriceps insufficiency in patients with knee compromise: How many velocities should an isokinetic test protocol consist of?

The objective of this study was to find out whether the use of multiple velocity (30, 60, 90 and 120°/s) isokinetic as well as a single angle isometric testing was justified for assessing unilateral muscular weakness. Twenty one unilateral knee patients (16 men, 5 women), mostly with ACL pathology, with a mean post-injury time of 36 ± 33 m, were conveniently sampled. All patients filled in a functional questionnaire which indicated good recovery. The relative weakness of the involved (I) side was determined using the uninvolved (U) side as reference. Patients were also asked to rank the difficulty in performing the tests. The mean (based on the 4 velocities) eccentric weakness (19.7%) was significantly higher than in both the concentric (14.9%) or the isomteric (13.9%) modes. However within either the concentric or eccentric modes no between-velocity differences were noted. Side dominance had a significant effect on quadriceps weakness in all test modes. In conclusion, and with respect to the specific patient group, the use of one or, at most, two test velocities is sufficient to portray muscular insufficiency.