Affiliations: [a] Yumemino Orthopedic Clinic, Toride-shi, Ibaraki 302-0039, Japan | [b] Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, Inashiki-gun, Ibaraki 300-0394, Japan | [c] Department of Cognitive Behavioral Physiology, Chiba University Graduate School of Medicine, Chiba-shi, Chiba 260-8670, Japan | [d] Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences Hospital, Inashiki-gun, Ibaraki 300-0394, Japan | [e] Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, Inashiki-gun, Ibaraki 300-0394, Japan | [f] Faculty of Rehabilitation, School of Healthcare, Fujita Health University, Toyoake-shi, Aichi 470-1192, Japan
Correspondence:
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Corresponding author: Daisuke Ishii, Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan. Tel.: +81 29 888 4000; E-mail: d-ishii@umin.ac.jpac.jp.
Abstract: BACKGROUND: Rotator cuff muscles are structurally and functionally different from other upper-limb muscles because they are responsible for glenohumeral joint stability. Neuromuscular electrical stimulation (NMES) induces excitability changes (increase or decrease) of the corticospinal tract (CST) in the peripheral muscles, such as those of the finger. However, it remains unclear whether similar results are obtained when targeting the infraspinatus muscle, which has properties that differ from other muscles, in healthy subjects. OBJECTIVE: We investigated the immediate effects of NMES on the corticospinal excitability of the infraspinatus muscle, a rotator cuff muscle, in healthy subjects. METHODS: Thirteen healthy right-handed men (mean age: 26.77 ± 2.08 years) participated in this study. The motor evoked potentials (MEPs) and the maximum compound muscle action potential (Mmax) were recorded before NMES to the right infraspinatus and within 15 minutes after the end of the NMES. RESULTS: NMES on the infraspinatus muscle significantly increased its MEP amplitude (Pre: 0.45 mV [0.33–0.48]; Post: 0.54 mV [0.46–0.60] (median [lower quartile to higher quartile]); p= 0.005) but had no effect on Mmax (Pre: 2.95 mV [2.59–4.71]; Post: 3.35 mV [2.76–4.72]; p= 0.753). CONCLUSIONS: NMES application to the infraspinatus muscle increases CST excitability without producing immediate changes in the neuromuscular junction or muscle hypertrophy.
Keywords: Infraspinatus muscle, rotator cuff muscles, electrical stimulation, transcranial magnetic stimulation, motor evoked potential
