Torque variations during repeated passive isokinetic knee movements in persons with multiple sclerosis

Area of Science:

• Biomechanics
• Neurorehabilitation
• Movement Science

Background:

• Multiple sclerosis (MS) often leads to hypertonia, affecting knee joint movement and posing challenges in rehabilitation.
• Understanding the mechanisms behind torque reduction during repetitive movements is crucial for optimizing physical therapy for MS patients.

Purpose of the Study:

• To investigate the impact of movement repetitions on knee resistive torque in individuals with MS and hypertonia.
• To explore the role of electromyographic (EMG) activity in stretched muscles during isokinetic dynamometry.

Main Methods:

• Passive isokinetic dynamometry of the knee was performed on 10 individuals with MS and hypertonia and 10 healthy controls.
• Subjects underwent series of 10 knee flexion and extension movements at 60, 180, and 300 degrees/s.
• Torque and EMG activity of stretched muscles were recorded during all movements.

Main Results:

• Individuals with hypertonia exhibited significantly greater torque reduction compared to controls across most tested conditions (p < 0.05).
• An exception was observed in repeated knee flexion at 300 degrees/s, where torque reduction differences were not significant.
• EMG activity in stretched muscles did not solely explain the observed torque reduction in hypertonic individuals.

Conclusions:

• Repetitive passive knee movements lead to a greater reduction in resistive torque in MS patients with hypertonia.
• Factors other than electromyographic activity in stretched muscles contribute to the modulation of hypertonia during repeated movements.
• These findings suggest potential targets for therapeutic interventions aimed at managing knee hypertonia in multiple sclerosis.