Altered Position Sense after Submaximal Eccentric Exercise-inducing Central Fatigue.

PURPOSE: The purpose of this study was to concomitantly investigate the acute and delayed effects of a submaximal eccentric-induced muscle fatigue on the position sense and the neuromuscular function of the right knee extensor muscles. METHODS: Thirteen young and physically active participants performed a unilateral isokinetic eccentric exercise of their right lower limb until a decrease in maximal voluntary isometric contraction (MVIC) of 20% was reached. Neuromuscular (i.e., MVIC, voluntary activation (VA) level, and evoked contractile properties [DB100 and DB10]) and psychophysical evaluations (i.e., bilateral position-matching task, perceived muscle soreness, and perceived fatigue) were performed at four time points: before (PRE), immediately after (POST), 24 (POST24), and 48 (POST48) the exercise. RESULTS: The acute 20% MVIC reduction (P < 0.001) was associated with both central (i.e., -13% VA decrease, P < 0.01) and peripheral (i.e., -18% and -42% reduction of DB100 and DB10, respectively, P < 0.001) fatigue. In the following days (POST24 and POST48), VA levels had recovered despite the presence of a persisting peripheral fatigue and delayed-onset muscle soreness. Knee position sense, as revealed by position errors, was significantly altered only at POST (P < 0.05) with participants overestimating the length of their knee extensor. Position errors and VA deficits were significantly correlated at POST (r = -0.60, P = 0.03). Position errors returned to nonsignificant control values in the following days. CONCLUSION: The acute central fatigue induced by the eccentric exercise contributes to the position sense disturbances. Central fatigue might lead to alterations in the sensory structures responsible for the integration and the processing of position-related sensory inputs.

Short-TERM Neuromuscular Electrical Stimulation Training of the Tibialis Anterior Did Not Improve Strength and Motor Function in Facioscapulohumeral Muscular Dystrophy Patients.

OBJECTIVE: The aim of this study was to investigate the effects on motor function, muscle strength, and endurance of short-term neuromuscular electrical stimulation training of the tibialis anterior muscles in patients with facioscapulohumeral muscular dystrophy type 1 (FSHD1) in comparison with healthy controls. DESIGN: This prospective study included 10 patients with FSHD1 and 10 healthy participants. Maximal voluntary isometric contraction of ankle dorsiflexion and a 2-min sustained dorsiflexion maximal voluntary contraction with surface electromyography recordings of the tibialis anterior and the soleus muscles were measured and motor function clinical tests were performed before and after the training period. RESULTS: No significant short term training effect was found in any of the investigated variables for either group, although a tendency towards an increase was noted for the manual muscle testing of the FSHD1. Patients with FSHD1 showed lower maximal voluntary contraction force and lower maximal tibialis anterior surface electromyography amplitude than healthy participants. During the 2-min sustained maximal voluntary contraction, the percentage of force loss was lower for the FSHD1 patients, suggesting that they were experiencing a lower amount of muscle fatigue compared to the healthy participant group. CONCLUSION: The present neuromuscular electrical stimulation protocol was not strenuous enough and/or the parameters of stimulation were not adequate to improve dorsiflexion strength, muscle endurance, and motor function in FSHD1 patients and healthy participants.

Neuromuscular electrical stimulation training: a safe and effective treatment for facioscapulohumeral muscular dystrophy patients.

OBJECTIVE: To investigate the feasibility, safety, and effectiveness of neuromuscular electrical stimulation (NMES) strength training in facioscapulohumeral muscular dystrophy (FSHD) patients. DESIGN: Uncontrolled before-after trial. SETTING: Neuromuscular disease center in a university hospital and a private-practice physical therapy office. PARTICIPANTS: FSHD patients (N=9; 3 women, 6 men; age 55.2+/-10.4y) clinically characterized by shoulder girdle and quadriceps femoris muscle weakness. INTERVENTIONS: Patients underwent 5 months of strength training with NMES bilaterally applied to the deltoideus, trapezius transversalis, vastus lateralis, and vastus medialis muscles for five 20-minute sessions per week. MAIN OUTCOME MEASURES: Plasma creatine kinase (CK) activity; scores for pain and fatigue on visual analog scales (VAS), manual muscle testing (MMT), maximal voluntary isometric contraction (MVIC), 6-minute walking tests (6MWT), and self-reported changes in daily living activities. RESULTS: NMES strength training was well tolerated (CK activity and pain and fatigue scores on VAS were not modified). Most of the muscle functions (shoulder flexion and extension and knee extension) assessed by MMT were significantly increased. MVIC of shoulder flexion and abduction and the 6MWT distance were also improved. CONCLUSIONS: In FSHD, NMES strength training appears to be safe with positive effects on muscle function, strength, and capacity for daily activities.