Enhanced neural drive after maximal strength training in multiple sclerosis patients

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 × 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 ≤ 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

Functional maximal strength training induces neural transfer to single-joint tasks

The purpose of this study was to investigate whether neural adaptations following functional multiplejoint leg press training can induce neural adaptations to the plantar Xexor 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 Xexion. 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-reXexes in the soleus during rest and 20% MVIC. One repetition maximum leg press increased by 44 ± 14% (mean ± SD; P < 0.01). Plantar Xexion MVIC increased by 20 ± 14% (P < 0.01), accompanied by 13 ± 19% (P < 0.05) increase in soleus, but not GM surface electromyography. Soleus V/MSUP increased by 53 ± 66% and in GM by 59 ± 64% (P < 0.05). Normalised soleus H-reXexes 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 Xexion MVIC task

Electromyographic comparison of the barbell deadlift using constant versus variable resistance in healthy, trained men.

Variable, external resistance is proposed to increasingly augment the muscular stress throughout a dynamic movement. However, it is uncertain how different levels of variable resistance affect the activation in the deadlift. The aim of the study was to compare the electromyographic activity of the gluteus maximus, biceps femoris, semitendinosus, vastus lateralis and erector spinae muscles during the barbell deadlift with free weights (FW) alone, with two (FW-2EB), and four elastic bands (FW-4EB) to deload some of the constant external resistance. Fifteen resistance-trained men participated in a cross-over design where resistance loadings were matched using two-repetition maximum loadings in the three different conditions. For the whole movement, both repetitions were analyzed. For the phase-specific analysis, the last repetition was divided into six parts, i.e. the lower, middle and upper phase in both the ascending and descending phase of the movement. The mean deloading contributions from FW-2EB and FW-4EB were 21% and 41%, respectively. In FW-4EB, the erector spinae was activated more in the whole movement (8%, ES = 0.31, p = 0.002) compared to FW-2EB. There was also a tendency towards higher activation in FW-4EB versus FW for the whole movement (5%, ES = 0.18, p = 0.072). There were no significant differences between the conditions in any of the other phases or muscles (p = 0.106-0.926). In summary, a high contribution from variable, external resistance seems to activate the back extensors more than a low contribution