Assessment of muscle fatigue in multiple sclerosis patients in electromyographic examinations.
Aleksandra Radecka, Anna Knyszyńska, Anna Lubkowska
PMID 36892519WHAT IT FOUND
During wrist fatigue tests, healthy people increased muscle signal amplitude to maintain force, but people with MS decreased it.
This suggests their muscles cannot recruit new units effectively. Therapists should not assume standard EMG fatigue patterns apply to MS patients.
Key findings
01In healthy controls, muscle signal amplitude increased during fatigue contraction, but in people with MS, it decreased.
02People with MS had significantly lower absolute muscle signal amplitude values than healthy controls during both extension and flexion.
03The frequency of the muscle signal decreased over time in both groups, indicating fatigue, but the decrease was smaller in the MS group for extensor muscles.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The groups were not perfectly age-matched (median age 30 vs 29), though the authors argue this is negligible for sEMG in young adults. The MS group had mild disability (EDSS 1-3) and was in remission, so results may not apply to those with severe disability or during relapse. The study cannot distinguish whether the signal changes are due to central nervous system issues or peripheral muscle changes. Skin impedance was not measured, which could theoretically affect signal quality, though skin preparation was standardized.
The easy way to misread this
Do not assume that a lack of amplitude increase in an MS patient's EMG means they are not fatiguing. It indicates a different physiological response, likely a failure to recruit additional motor units, which is a distinct problem from the compensatory increase seen in healthy muscles.