Abstract
The purpose of this study was to examine the appropriateness of isokinetic assessment in patients with multiple sclerosis (MS). We tested a group of 15 patients with a value of 2 to 3 on the Kurtzke disability status scale (DSS) and we compared that group with a similar healthy age- and weight-matched control group. All the patients underwent a maximal isokinetic test of knee flexion and extension at the angular speeds of 120 deg/sec, 60 deg/sec, and an endurance and work recovery test at 180 deg/sec. Data were collected using a Cybex 350.
Several muscular parameters relating to peak torque, work, and power were assessed. There were significant differences of these group results on most of the measured parameters. There was a deficit of 46% in peak torque in flexion and 30% in extension, thought to be related to the deficit in motor unit recruitment. Moreover, in comparison with the control group, the total work at 180 deg/sec (−55%) and the average muscular power (−45%) were significantly impaired. The higher deficit of the flexors compared with the extensors may be related to both the hypertonicity rate of the quadriceps and disturbances of reciprocal inhibition time during the alternate movement. From a morphological point of view it appears as a deficit in the muscle tension development in the initial part of the flexion curve. Our results, in contrast, do not show significant differences between the two groups in relation to endurance ratio and work recovery. This is in contrast to the increased fatigability commonly reported by MS patients. The explanation could be that fatigue in this disease has a mainly central origin, due to the impairment in motor control, whereas by means of isokinetic methods we explore the peripheral muscle fatigue linked to the muscular energy exhaustion.