Fatigue in complete spinal cord injury and implications on total delay

Abstract

The use of neuromuscular electrical stimulation (NMES) to artificially restore movement in people with complete spinal cord injury (SCI) induces an accelerated process of muscle fatigue. Fatigue increases the time between the beginning of NMES and the onset of muscle force (DelayTOT). Understanding how much muscle fatigue affects the DelayTOT in people with SCI could help in the design of closed‐loop neuroprostheses that compensate for this delay, thus making the control system more stable. The aim of this study was to evaluate the impact of the extent of fatigue on DelayTOT and peak force of the lower limbs in people with complete SCI. Fifteen men—young adults with complete SCI (paraplegia and tetraplegia) and stable health—participated in the experiment. DelayTOT was defined as the time interval between the beginning of NMES application until the onset of muscle force. The electrical intensity of NMES applied was adjusted individually and consisted of the amplitude required to obtain a full extension of the knee (0°), considering the maximum electrically stimulated extension (MESE). Subsequently, 70% of the MESE was applied during the fatigue induction protocol. Significant differences were identified between the moments before and after the fatigue protocol, both for peak force (P ≤ .026) and DelayTOT (P ≤ .001). The medians and interquartile range of the DelayTOT were higher in postfatigue (199.0 ms) when compared to the moment before fatigue (146.5 ms). The medians and interquartile range of the peak force were higher in unfatigued lower limbs (0.43 kgf) when compared to the moment postfatigue (0.27 kgf). The results support the hypothesis that muscle fatigue influences the increase in DelayTOT and decrease in force production in people with SCI. For future applications, the combined evaluation of the delay and force in SCI patients provides valuable feedback for NMES paradigms. The study will provide potentially critical muscle mechanical evidence for the investigation of the evolution of atrophy.

A Novel Framework for Quantifying Accuracy and Precision of Event Detection Algorithms in FES-Cycling

“…Normalising delays in detection by the duration of the cycle in question allows for the criterion to ensure comparability throughout different cycles and sessions. A value of ±10% for the criterion was considered strict enough, compared to the variations of other existing delays in neuromuscular electrical stimulation (NMES) [ 12 , 13 , 34 , 35 ]. Rinaldin et al (2020) [ 12 ] showed that muscular fatigue increased significantly the delay from onset of muscle stimulation to muscular force production in SCI participants from averages of 146.50 ms pre-fatigue to 199.0 ms post-fatigue.…”

“…A value of ±10% for the criterion was considered strict enough, compared to the variations of other existing delays in neuromuscular electrical stimulation (NMES) [ 12 , 13 , 34 , 35 ]. Rinaldin et al (2020) [ 12 ] showed that muscular fatigue increased significantly the delay from onset of muscle stimulation to muscular force production in SCI participants from averages of 146.50 ms pre-fatigue to 199.0 ms post-fatigue. Sinclair et al (2004) [ 35 ] also showed that both rise time and rise delay in muscle force production change depending on the angle of the knee at which the contraction is produced, averages ranging from 31 ± 3 ms to 67 ± 24 ms for rising delay and 72 ± 14 ms to 140 ± 62 ms for rising time, taking into account inter-subject variability.…”

“…In this context, a stimulation pattern that correlates the measured crank angle to the individual muscles’ activation is usually preset and adjusted empirically in a time-consuming process [ 11 ]. Furthermore, several variables are still subject to change throughout a cycling session, for instance, the time delay in muscular force production, which can be affected by muscle fatigue [ 12 ]. Synchronising muscle-stimulation-triggering events in relation to the crank angle presumes a fixed geometrical model dependent on the pilot’s anatomy and seating position [ 13 ].…”

Neuromuscular fatigue detection by mechanomyography in people with complete spinal cord injury

“…When the knee reached full extension, the exact FES amplitude was registered as the maximum electrically stimulated extension voltage. This procedure was previously used in our experiments and named as maximum safety force (Rinaldin et al 2020). After the load cell rigid attachment, the same FES intensity (MESE) was applied again, and the output voltage of the load cell was assumed to be the reference, F 100% .…”