Article

Results of previous studies raise the question of how timing neuromuscular
functional electrical stimulation (FES) to limb movements during stepping might
alter neuromuscular control differently than patterned stimulation alone. We have
developed a prototype FES system for a rodent model of spinal cord injury (SCI)
that times FES to robotic treadmill training (RTT). In this study, one group of
rats (n = 6) was trained with our FES+RTT system and received stimulation of the
ankle flexor (tibialis anterior [TA]) muscle timed according to robot-controlled
hind-limb position (FES+RTT group); a second group (n = 5) received a similarly
patterned stimulation, randomly timed with respect to the rats' hind-limb
movements, while they were in their cages (randomly timed stimulation [RS]
group). After 4 wk of training, we tested treadmill stepping ability and compared
kinematic measures of hind-limb movement and electromyography (EMG) activity in
the TA. The FES+RTT group stepped faster and exhibited TA EMG profiles that
better matched the applied stimulation profile during training than the RS group.
The shape of the EMG profile was assessed by "gamma," a measure that quantified
the concentration of EMG activity during the early swing phase of the gait cycle.
This gamma measure was 112% higher for the FES+RTT group than for the RS group.
The FES+RTT group exhibited burst-to-step latencies that were 41% shorter and
correspondingly exhibited a greater tendency to perform ankle flexion movements
during stepping than the RS group, as measured by the percentage of time the hind
limb was either dragging or in withdrawal. The results from this study support
the hypothesis that locomotor training consisting of FES timed to hind-limb
movement improves the activation of hind-limb muscle more so than RS alone. Our
rodent FES+RTT system can serve as a tool to help further develop this combined
therapy to target appropriate neurophysiological changes for locomotor control.

Langue : ANGLAIS