Enhanced neural drive after maximal strength training in multiple sclerosis patients

Abstract

Multiple sclerosis (MS) patients suffer from impaired muscle activation and lower limb strength. Strength training enhances muscle activation and muscle strength, but neural adaptations to strength training remain unexplored in MS patients. The hypothesis was that maximal strength training (MST) using high loads and few repetitions would improve central neural drive and thus strength capacity of MS patients. 14 MS patients staying at a national MS rehabilitation center were randomly assigned to a MST group or a control group (CG). Both groups received "today's treatment". In addition, the MST group trained 4 x 4 repetitions of unilateral dynamic leg press and plantar flexion 5 days a week for 3 weeks. Neural adaptations of the soleus muscle were assessed by surface electromyography (EMG) activity, and by superimposed H-reflexes and V-waves obtained during maximum voluntary isometric plantar flexor contractions (MVCs). H-reflexes and V-waves were normalized by the M-wave (H(SUP)/M(SUP), V/M(SUP), respectively). In the MST group, MVC increased by 20 +/- 9% (P < 0.05). Soleus EMG activity and V/M(SUP) ratio increased by 40 and 55%, respectively, in the MST group compared to the CG (P <or= 0.05). The H(SUP)/M(SUP) ratio remained unchanged. No change was apparent in the CG. MST group subjects were able to complete all training sessions. No adverse effects were reported. This randomized study provides evidence that MST is effective of augmenting the magnitude of efferent motor output of spinal motor neurons in MS patients, alleviating some neuromuscular symptoms linked to the disease.

Strength training-induced responses in older adults: attenuation of descending neural drive with age

“…While the importance of neural factors in strength training in the elderly population should yet be treated with some caution because of the low sample size and limited muscle groups studied in the current study, recommendations of heavy resistance training with emphasis on maximal mobilization in the concentric phase has provided excellent results not only in this study, but in a wide range of untrained patient populations (de Vos et al 2005;Hoff et al 2007;Caserotti et al 2008;Husby et al 2009;Fimland et al 2010;Fimland et al 2011;Heggelund et al 2012;Hill et al 2012;Mosti et al 2013). Although the isometric training may also account for some of the adaptations, these studies together present mounting evidence that heavy resistance training not only is feasible and effective; additionally, no incidents of injury have been reported.…”

“…Importantly, the dynamic exercises were carried out with a controlled eccentric phase of the movement, a short stop, and maximal mobilization of force in the concentric phase. This movement pattern has been frequently used in our laboratory to facilitate neuromuscular adaptations to resistance training (Hoff et al 2007;Storen et al 2008;Fimland et al 2009Fimland et al , 2010. To facilitate maximal intended velocity, 3-min resting periods were applied between each set, while each exercise was separated by 5-min rest.…”

“…Indeed, this is an important aspect since it also reflects the changes of the fast twitch muscle fibers, which are closely linked to balance adjustments and fall prevention (Hvid et al 2010). The V-wave methodology, an electrophysiological variant of the H-reflex technique, evoked in the triceps surae muscles during maximal muscle contraction has been applied for this frame of testing in several studies (Upton et al 1971;Aagaard et al 2002;Duclay and Martin 2005;Fimland et al 2009;Ekblom 2010;Fimland et al 2010;Fimland et al 2011;Vila-Cha et al 2012). The V-wave is typically normalized to the maximal M-wave (V/M ratio), and its magnitude is suggested to reflect neural drive to the muscle, as well as spinal excitability and pre/ postsynaptic inhibition (Upton et al 1971;Aagaard et al 2002;Aagaard 2003).…”

Effects of high-speed power training on muscle strength and power in patients with multiple sclerosis

“…The results showed no significant changes in the control group from baseline to postintervention evaluation. In contrast, the exercise group significantly increased MVIC (10.8%; p < 0.05) and muscle power at 40,50, 60, 70, and 80% of the MVIC by 21.8, 14.5, 17.3, 19.4,and 22.3%, respectively (p < 0.01), after the training. These findings suggest that 12 wk of high-speed power training improve both MVIC and muscle power at five different loads in patients with relapsing-remitting MS.…”

The effect of exercise therapy on fatigue in multiple sclerosis

“…Efferent high-frequency fatigue is thereby prevented, but the maximal muscle strength is also reduced. 43,44 In healthy subjects RT improves central motor activation, 45 in MS patients RT enhances the efferent motor drive, 46 and in MS RT seems to reduce MS fatigue. The perception of worsened fatigue after overtraining may occur as a consequence of afferent inhibition from strained muscles.…”