Baclofen effect on quadriceps strength in multiple sclerosis

Weakness has been reported by patients as one side effect of baclofen. We evaluated torque production as a measure of contractile strength in 30 subjects with clinically definite multiple sclerosis. Participants, with minimal to moderate spasticity, were titrated onto baclofen by 5mg increments every other day for seven days and maintained at 20mg for one week. Using a KinCom isokinetic unit set at 60 degrees per second, subjects performed maximal concentric quadriceps contractions; three consecutive trials were recorded. Results indicated no significant difference in maximum torque production between sessions. Although torque values remained unchanged, the angle at which peak torque production occurred moved closer to normal values. Subjective reports of weakness do not appear related to physiologic properties of contraction, but may be a subjective interpretation that less stiffness is weakness because of less resistance to muscle contraction.