Increased antagonist muscle activity in cervical SCI patients suggests altered reciprocal inhibition during elbow contractions.
OBJECTIVE
After spinal cord injury (SCI), the antagonist muscles activation is increased during voluntary contractions and reflex conditioning protocols. This increase can be the result of both muscle atrophy and reciprocal facilitation mechanism. It remains however unclear to what extent increased antagonist muscles activation could be rather attributable to central vs. peripheral changes during voluntary contractions achieved by SCI participants.


METHODS
We investigated the activations of elbow extensors and flexors during isometric elbow flexion and extension contractions performed at 3 force levels by 10 healthy participants and 8 participants with cervical SCI (cSCI).


RESULTS
At similar force level and absolute net torque in flexion, the antagonist muscles activation was increased for the participants with cSCI. At similar absolute net torque in extension, the activations of agonist and antagonist muscles were increased for the participants with cSCI.


CONCLUSIONS
During flexion contractions, increased antagonist muscles activation may be explained by extensors atrophy or reciprocal facilitation. During extension contractions, increased antagonist muscles activation may reflect the importance of reciprocal facilitation as antagonist muscles were evaluated as intact by clinical testing and maximal net joint torque recording.


CONCLUSIONS
These results in cSCI participants revealed an increased activation of antagonist muscles, which may reflect a reorganization of the spinal reflexes and their supraspinal control involved during isometric elbow contractions.
Aix-Marseille Université, CNRS, ISM UMR 7287, Marseille, France; PRISSMH-LAPMA, Université de Toulouse, UPS, Toulouse, France; LAMIH, UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis, Valenciennes, France. Electronic address: sylvain.cremoux@univ-valenciennes.fr.
Sylvain
S
Cremoux
Inserm, Imagerie cérébrale et handicaps neurologiques, UMR 825, Toulouse, France; Université de Toulouse, UPS, Imagerie cérébrale et handicaps neurologiques, UMR 825, Toulouse, France. Electronic address: david.amarantini@inserm.fr.
David
D
Amarantini
PRISSMH-LAPMA, Université de Toulouse, UPS, Toulouse, France. Electronic address: jessica.tallet@univ-tlse3.fr.
Jessica
J
Tallet
Laboratoire de Simulation et Modélisation du Mouvement, Département de Kinésiologie, Université de Montréal, Canada. Electronic address: fabien.dalmaso@gmail.com.
Fabien
F
Dal Maso
Aix-Marseille Université, CNRS, ISM UMR 7287, Marseille, France. Electronic address: eric.berton@univ-amu.fr.
Eric
E
Berton
D000328:Adult; D002574:Cervical Vertebrae; D004551:Elbow Joint / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000175:diagnosis* / Q000503:physiopathology*; D019415:Torque
Agonist and antagonist muscles; Elbow flexors and extensors; Electromyography; Force level; Isometric contractions