| 总结: | Functional electrical stimulation (FES)-evoked cycling has been reported to enhance
muscle strength and fatigue resistance after spinal cord injury (SCI). Its goal is to
produce the highest possible power to maximize physiological benefits. With the tuning
between the foot and pedal contact point to the relative strength of the ankle plantar
flexors, power production was simulated to be improved by 14% by releasing the ankle
joint from a fixed ankle setup and with the stimulation of the tibialis anterior and triceps
surae. FES-evoked cycling however produces very low power and efficiency in
individuals with SCI compared to healthy individuals. This is because of the early onset
of muscle fatigue among individuals with SCI. To date, muscle fatigue during FESevoked
cycling in individuals with SCI has been quantified in many studies by means of
peak torque or pedal power output (PO) decrement. These measures may not be
sensitive and do not reflect metabolic markers of fatigue. This study aimed to
experimentally determine the effect of releasing the ankle joint on the pedal power
production during FES-evoked cycling in individuals with SCI. This study also aimed to
examine the relationship between the vibrational performance of electrically-evoked
muscles measured through mechanomyography (MMG) and its oxidative metabolism
through near-infrared spectroscopy (NIRS) characteristics during FES-evoked cycling
in individuals with SCI. This study also sought to quantify muscle fatigue during FESevoked
cycling using MMG and NIRS. Seven individuals with motor complete SCI
participated in this study. In achieving the first objective of this study, all participants
performed one minute of fixed-ankle and free-ankle FES-evoked cycling with two
stimulation modes. In Mode 1, participants performed FES-evoked cycling with the stimulation of quadriceps and hamstring muscles only (QH stimulation), while Mode 2
had stimulation of quadriceps, hamstring, tibialis anterior, and triceps surae muscles
(QHT stimulation). Free-ankle FES-evoked cycling offered greater ankle plantar- and
dorsiflexion at specific slices of 20° crank angle intervals compared to fixed-ankle.
Fixed-ankle QHT stimulation elevated the peak normalized pedal PO by 14.5% more
than free-ankle QH stimulation. Releasing the ankle joint without the stimulation of
triceps surae and tibialis anterior reduces PO. The findings of this study suggest that
QHT stimulation is necessary during free-ankle FES-evoked cycling to maintain power
production as fixed-ankle. For the second and third objectives, all participants
performed 30 minutes of FES-evoked cycling with MMG and NIRS sensors on their
quadriceps throughout the cycling, and the signals were analyzed. A moderate
significant negative correlation was found between MMG root mean square (RMS) and
oxyhaemoglobin (O2Hb) [r = -0.38, p = 0.003], and RMS and total haemoglobin (tHb)
saturation [r = -0.31, p = 0.017]. There were significant differences in RMS, O2Hb, and
tHb saturation during pre- and post-fatigue of FES-evoked cycling (p < 0.05). MMG
RMS was negatively associated with O2Hb and muscle oxygen derived from NIRS.
MMG and NIRS sensors showed good inter-correlations with each other, suggesting a
promising use of MMG for characterizing metabolic fatigue at the muscle oxygenation
level during FES-evoked cycling in individuals with SCI.
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