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The purpose of this study was to investigate whether neural adaptations following functional multiple-joint leg press training can induce neural adaptations to the plantar flexor muscles in a single-joint contraction task. Subjects were randomised to a maximal strength training (MST) (n = 10) or a control group (n = 9). MST consisted of 24 sessions (8 weeks) of 4 x 4 repetitions of horizontal leg press using maximal intended velocity in the concentric phase with the movement ending in a plantar flexion. Neural adaptations in the soleus and gastrocnemius medialis (GM) were assessed by surface electromyographic activity and V-waves during maximum voluntary isometric contraction (MVIC), and also by H- reflexes in the soleus during rest and 20% MVIC. One repetition maximum leg press increased by 44 +/- A 14% (mean +/- A SD; P < 0.01). Plantar flexion MVIC increased by 20 +/- A 14% (P < 0.01), accompanied by 13 +/- A 19% (P < 0.05) increase in soleus, but not GM surface electromyography. Soleus V/M-SUP increased by 53 +/- A 66% and in GM by 59 +/- A 64% (P < 0.05). Normalised soleus H-reflexes remained unchanged by training. No changes occurred in the control group. These results suggest that leg press MST can induce neural adaptations in a single-joint plantar flexion MVIC task.
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 +/- A 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 a parts per thousand currency sign 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.