Neural and muscular mechanisms of electrically induced fatigue in patients with spinal cord injury.
METHODS
Intervention study.


OBJECTIVE
The present study aimed at examining whether spinal and/or peripheral alterations are in the origin of neuromuscular fatigue development induced by intermittent neuromuscular electrical stimulation (NMES) in subjects with complete spinal cord injury (SCI).


METHODS
Neurological Rehabilitation Center CMN Propara, Montpellier, France.


METHODS
Thirteen volunteers with complete SCI participated in the study. The right triceps surae muscle was fatigued using a 30-Hz NMES protocol (2 s ON-2 s OFF) composed of three series of five trains. Spinal excitability (assessed by the H-reflex), muscle excitability (assessed by the M-wave), muscle contractile properties (assessed by mechanical response parameters) and torque evoked by NMES were tested before and after each five-train series.


RESULTS
NMES-evoked torque significantly decreased throughout the protocol (P<0.001). This decrease was accompanied by a significant increase in M-wave amplitude (P<0.001), whereas H-reflex and the Hmax/Mmax ratio were not significantly modified. The amplitude of the mechanical response was significantly decreased at the end of the protocol (P<0.05).


CONCLUSIONS
The results indicate significant fatigue development, which was attributed to impaired cross-bridge force-generating capacity, without modification of spinal excitability nor muscle excitability.
1] EA2991 Movement to Health, Montpellier-1 University, EuroMov, Montpellier, France [2] Aix-Marseille University, CNRS, ISM UMR 7287, Faculté des Sciences du Sport, Marseille, France.
M
M
Papaiordanidou
EA2991 Movement to Health, Montpellier-1 University, EuroMov, Montpellier, France.
A
A
Varray
Centre Mutualiste Neurologique Propara, Montpellier, France.
C
C
Fattal
LIRMM, DEMAR team, INRIA, Montpellier, France.
D
D
Guiraud
D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology*; D010264:Paraplegia / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000534:rehabilitation