Fatigue induces altered spatial myoelectric activation patterns in the medial gastrocnemius during locomotion

Abstract

Sustained voluntary muscle contractions can lead to fatigue, which diminishes the muscle's ability to absorb energy and produce force at a desired level. Prolonged fatigue can lead to a decline in human performance and increase the muscle's susceptibility to injury. In this study, we investigated how localized muscle fatigue affected spatial EMG patterns during locomotion. We recorded high-density electromyography (EMG) from the medial gastrocnemius of 11 healthy subjects while they walked (1.2 m/s) and ran (3.0 m/s) on a treadmill before and after performing a task that locally fatigued their ankle plantarflexor muscles. We applied multivariate signal cleaning methods to remove motion artifacts from the recorded signals. From these data, we computed the peak EMG amplitude, spatial entropy, peak EMG barycenter, and mean power frequency content during walking and running before and after subjects fatigued. We also calculated sagittal plane lower limb joint kinematics and kinetics in each condition. We found that peak EMG activity significantly decreased during walking and running after the fatigue task, and the location of the peak EMG barycenter had shifted proximally compared to its pre-fatigue location. We also observed an increase in the EMG mean power frequency during locomotion post-fatigue. Despite the changes in spatial EMG activation, lower limb biomechanics were similar before and after fatigue. These results suggest that motor unit recruitment was altered to sustain force production and forward propulsion. This may be a protective mechanism to more broadly distribute muscle loads and avoid myotendinous injury.

Feedforward and Feedback Function of Selected Lower Limb Muscles Following Plyometric Exercises and Cryotherapy

“…Therefore, the decrease in the activity of the internal gastrocnemius muscle in the plyometric group can confirm the nervous fatigue caused by the plyometric training, which, as a result, reduces the use of muscle motor units [31]. Some other studies have shown the effect of fatigue on the decrease in muscle activity [32,33] which is associated with an increased chance of anterior cruciate ligament (ACL) injury [34]. The medial gastrocnemius muscle is one of the main muscles in the concentric phase for functional performance.…”

Directed Information Flow Analysis Reveals Muscle Fatigue-Related Changes in Muscle Networks and Corticomuscular Coupling

“…Similarly, for submaximal contraction, due to the decrease in force generation capacity during muscle fatigue, the increases in sEMG amplitude and energy were considered to reflect increased recruitment of additional motor units to maintain the strength level (Liu et al, 2003;Yang et al, 2009). Recently, Schlink et al (2021) observed that fatigue induces altered EMG activation patterns in the medial gastrocnemius. They confirmed that this may be a protective mechanism of the neuromuscular system to avoid muscle injury by distributing the muscle load more broadly.…”

The use of nonnormalized surface EMG and feature inputs for LSTM-based powered ankle prosthesis control algorithm development

“…This can serve limiting the computation cost of normalization, which needs to be tested in new studies. However, prolonged walking has been shown to cause muscle fatigue ( Chambers et al, 2019 ) and consequently decreased sEMG amplitudes ( Schlink et al, 2021 ). More importantly, studies have shown variations in sEMG amplitudes with changes in walking speed ( den Otter et al, 2004 ), which may compromise accuracy of static reference values.…”