Effects of electrically induced muscle contraction on flexion reflex in human spinal cord injury.
METHODS
Flexion reflex study in motor complete human spinal cord injury (SCI).


OBJECTIVE
To examine changes in the magnitude of the flexion reflex following functional electrical stimulation (FES) of the rectus femoris (RF) muscle.


METHODS
Bioengineering Unit, University of Strathclyde, Glasgow, Scotland, UK.


METHODS
The flexion reflex was evoked by electrical stimulation of the sural nerve, and was recorded in the tibialis anterior (TA) muscle. RF muscle conditioning stimulation was performed at 0.7, 1, and 2 times motor threshold ( x MT) over a range of conditioning test intervals.


RESULTS
The incidence of the early component of the flexion reflex (<100 ms) was low, suggesting that this reflex component might be suppressed in SCI. The long latency flexion reflex component (>120 ms) was observed in all subjects during control conditions and following sensorimotor conditioning. FES applied to the RF muscle (above and below MT) in the main induced a significant early and long lasting depression of the long latency flexion reflex.


CONCLUSIONS
The depression of the flexion reflex was a result of multisensory actions on flexion reflex pathways resulting from the direct and indirect (mechanical) consequences of electrically induced muscle contraction on cutaneous and muscle afferents. Our findings emphasize the importance of sensory feedback mechanisms in modulating flexion reflex excitability, and highlight the need for rehabilitation professionals to consider the central actions of FES-induced afferent feedback when incorporating FES into a rehabilitation program.


BACKGROUND
State Scholarships Foundation (IKY) of Hellas.
Knikou
M
M
Biology, Programs in Physical Therapy, College of Staten Island, City University of New York, Staten Island, NY 10314, USA.
Conway
B A
BA
D000328:Adult; D004558:Electric Stimulation / Q000379:methods*; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology / Q000528:radiation effects*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D012018:Reflex / Q000502:physiology / Q000528:radiation effects*; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013360:Subliminal Stimulation; D013497:Sural Nerve / Q000528:radiation effects