Muscle activation varies with contraction mode in human spinal cord injury.
BACKGROUND
To better understand volitional force generation after chronic incomplete spinal cord injury (SCI), we examined muscle activation during single and repeated isometric, concentric, and eccentric knee extensor (KE) maximal voluntary contractions (MVCs).


METHODS
Torque and electromyographic (EMG) activity were recorded during single and repeated isometric and dynamic KE MVCs in 11 SCI subjects. Central activation ratios (CARs) were calculated for all contraction modes in SCI subjects and 11 healthy controls.


RESULTS
SCI subjects generated greater torque, KE EMG, and CARs during single eccentric vs. isometric and concentric MVCs (all P < 0.05). Torque and EMG remained similar during repeated eccentric MVCs; however, both increased during repeated isometric (>25%) and concentric (>30%) MVCs.


CONCLUSIONS
SCI subjects demonstrated greater muscle activation during eccentric MVCs vs. isometric and concentric MVCs. This pattern of activation contrasts with the decreased eccentric activation demonstrated by healthy controls. Such information may aid development of novel rehabilitation interventions.
Graduate Program in Neuroscience, University of Illinois at Chicago, 1919 West Taylor Street, M/C 898, Chicago, Illinois, 60612, USA.
Hyosub E
HE
Kim
Christopher K
CK
Thompson
T George
TG
Hornby
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000473:pathology* / Q000503:physiopathology*; D013223:Statistics as Topic; D019415:Torque
central activation ratio; eccentric contraction; fatigue; spasticity; spinal cord injury