Scott Delp et al conducted a study aimed at reducing joint loading in patients by using musculoskeletal simulations to identify simple changes in muscle coordination that could be taught to patients through electromyographic(EMG) activity feedback. The study showed that healthy individuals could reduce the ratio of gastrocnemius to soleus muscle activation by 25±15% (p=0.004) with simple biofeedback of EMG activity.
Delp’s muscle coordination retraining experiment involved individuals that had no history of lower limb injury within the past year. Participants visited a motion capture lab with a force-instrumented treadmill, an 11-camera motion capture system, and a wireless surface EMG system. Markers were placed on various muscles for limb tracking and EMG electrodes were also placed on participants legs for analysis and biofeedback purposes.
The participants performed five six-minute walking trials: a baseline trial, three feedback trials, and a retention trial. For the baseline walking trial, the participants were asked to walk naturally. Their baseline gastrocnemius-to-soleus activation ratio and baseline stance-phase-averaged gastrocnemius EMG linear envelope was calculated. During the first feedback trial, a real-time bar plot was used to instruct participants to reduce their activation rate by at least 15% relative to the baseline. The participants were also told to explore different coordination strategies during the first four minutes of the trial, to focus on their most successful strategy during the fifth minute, and to maintain the most successful strategy after feedback was removed at the sixth minute. During the second and third feedback trials, individuals were provided feedback on their gastrocnemius activity and were instructed to continue reducing their activation ratio by reducing gastrocnemius activation. During the retention trial, the feedback was removed, but the participants were instructed to walk with the same coordination pattern that they had learned during the feedback trials.
The study shows that simple changes in coordination can help with muscle retraining to reduce knee contact force and knee loading. Healthy individuals are able to change the relative activation of their gastrocnemius and soleus muscles with simple biofeedback of their muscle activity. “The change in coordination resulted in a 12% reduction in simulation-estimated knee contact force that may have therapeutic benefit for individuals with knee osteoarthritis. These results suggest that simulation-based intervention design is a promising tool for identifying new, learnable coordination strategies that achieve a therapeutic objective.”
DEFINITION OF EMG
According to Johns Hopkins Medicine, Electromyography (EMG) measures muscle response or electrical activity in response to a nerve’s stimulation of the muscle. The test is used to help detect neuromuscular abnormalities.
https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/electromyography-emg#:~:text=Electromyography%20(EMG)%20measures%20muscle%20response,the%20skin%20into%20the%20muscle.
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