DOI: 10.1249/mss.0000000000004050 ISSN: 0195-9131

Age-Related Modulation of Intermuscular Electromyographic Coherence across the Rotator Cuff and Deltoid Muscles during Fatigue

Huiying Zhu, Xin Yu, Lisa Griffin
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Background:

The preservation of shoulder muscle function is essential for independent daily living throughout the lifespan. Intermuscular electromyographic coherence analysis provides a measure of shared neural input across motor neuron pools, providing insight into neuromuscular control strategies of shoulder muscles, which is important as changes occur during aging.

Methods:

Younger ( n = 18, 24 ± 5 yrs) and older ( n = 20, 71 ± 6 yrs) adults performed an isometric contraction at 30° of shoulder scaption, maintaining 25% of their maximal voluntary contraction until task failure. Intermuscular EMG coherence was measured in three muscle pairs of the dominant shoulder (supraspinatus-infraspinatus, supraspinatus-middle deltoid, and infraspinatus-middle deltoid) during the initial and final 30 s of the fatigue task.

Results:

There was a significant increase in alpha- and beta-band coherence during fatigue in both age groups across all muscle pairs. However, beta-band coherence was significantly lower in the older adults than in the younger adults across all muscle pairs and fatigue phases.

Conclusions:

The results of this study show that older adults have reduced common oscillatory drive from the corticospinal pathway to the shoulder muscles. However, common cortical and subcortical drive to rotator cuff and deltoid muscles increase in both age groups to sustain muscle force during fatigue.

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