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Updated: Apr 27, 2026
Utility of Dissociated Intrinsic Hand Muscle Atrophy in the Diagnosis of Amyotrophic Lateral Sclerosis
Published on: March 4, 2014
EMG-force relation in the first dorsal interosseous muscle of patients with amyotrophic lateral sclerosis
Faezeh Jahanmiri-Nezhad1, Xiaogang Hu2, Nina L Suresh2
1Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA.
Background And Purpose:
The relationship between surface electromyography (EMG) and muscle force is essential to assess muscle function and its deficits. However, few studies have explored the EMG-force relation in patients with amyotrophic lateral sclerosis (ALS). The purpose of this study was to examine the EMG-force relation in ALS subjects and its alteration in comparison with healthy control subjects.
Methods:
Surface EMG and force signals were recorded while 10 ALS and 10 age-matched healthy control subjects produced isometric voluntary contractions in the first dorsal interosseous (FDI) muscle over the full range of activation. A linear fit of the EMG-force relation was evaluated through the normalized root mean square error (RMSE) between the experimental and predicted EMG amplitudes. The EMG-force relation was compared between the ALS and the healthy control subjects.
Results:
With a linear fit, the normalized RMSE between the experimental and predicted EMG amplitudes was 9.6 ± 3.6% for the healthy control subjects and 12.3 ± 8.0% for the ALS subjects. The slope of the linear fit was 2.9 ± 2.2 μVN-1 for the ALS subjects and was significantly shallower (p < 0.05) than the control subjects (5.1 ± 1.8 μVN-1). However, after excluding the four ALS subjects who had very weak maximum force, the slope for the remaining ALS subjects was 3.5 ± 2.2 μVN-1 and was not significantly different from the control subjects (p > 0.05).
Conclusions:
A linear fit can be used to well describe the EMG-force relation for the FDI muscle of both ALS and healthy control subjects. A variety of processes may work together in ALS that can adversely affect the EMG-force relation.
