Can strength training modify voluntary activation, contractile properties and spasticity in Multiple Sclerosis?: A randomized controlled trial.

Background: A randomized controlled trial was conducted to analyze the effects of 10 weeks of strength training (ST) on voluntary activation, muscle activity, muscle contractile properties, and spasticity in people with MS. Methods: 30 participants were randomized to either an experimental [EG] (n = 18) or a control [CG] (n = 12) group. The EG carried out 10-weeks of ST, where the concentric phase was performed at maximum voluntary velocity. Muscle activity of the vastus lateralis (surface electromyography (sEMG) during the first 200 ms of contraction), maximal neural drive (peak sEMG), voluntary activation (central activation ratio), and muscle contractile function (via electrical stimulation) of the knee extensor muscles, as well as spasticity, were measured pre-and post-intervention. Results: The EG showed a significant improvement with differences between groups in muscle activity in EMG(0-200) (p = 0.031; ES =-0.8) and maximal neural drive (p = 0.038; ES =-0.8), as well as improvement in the ST group with a trend towards significance in EMG(0-100)(p = 0.068; ES =-0.6). CAR increased after intervention in ST group (p = 0.010; ES=-0.4). Spasticity also improved in the ST group, with differences between group after intervention, in first swing excursion (right leg: p = 0.006; ES =-1.4, left leg: p = 0.031; ES =-1.2), number of oscillations (right leg: p = 0.001; ES =-0.4, left leg: p = 0.031; ES =-0.4) and duration of oscillations (left leg: p = 0.002; ES =-0.6). Contractile properties remain unchanged in both ST group and CG. Conclusions: 10 weeks of ST improves muscle activity during the first 200 ms of contraction, maximal neural conduction, and spasticity in people with MS. However, ST does not produce adaptations in muscle contractile properties in this population.