Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site

Abstract

Purpose: To identify the optimal stimulation site and technique for inducing strong muscle contraction using a high-frequency magnetic stimulator. Methods: High-frequency magnetic stimulation was administered to the right vastus lateralis (VL) of eight healthy adults at maximal intensity within the range of tolerable pain. The stimulation sites were as follows: section A, the area between the lateral edge of the base of the patella (LEBP) and the distal one-third of the thigh (point D); section B, the area between point D and the proximal one-third of the thigh (point P). Isometric maximal muscle contraction forces induced by magnetic stimulation (Stim-MCF) were compared between the two sections. Results: The Stim-MCF was significantly higher in section B than in section A. Additionally, the sites susceptible to stimulation were confined to a narrow area near point D in section A and the central part between points D and P in section B. The degree of pain was very low in both sections. Conclusion:The optimal site for magnetic stimulation of the VL was limited to the central part of the thigh. In addition to the superficial proximal sub-branch, the deep proximal sub-branch and/or deeply clustered motor nerve endings may have been stimulated. Our results suggested that moving the probe was a useful way to identify the site that elicited the strongest muscle contraction force.

Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators

“…The right vastus lateralis (VL) was magnetically stimulated according to previous reports [17,[20][21][22][23]. Participants were seated with their right knee and hip joints flexed at 75°.…”

“…Thus, rPMS intervention studies have inconsistent results and are limited in number compared with studies on electrical stimulation. We have previously examined the stimulation methods, such the intensity and application site, and confirmed that strong muscle contraction can be obtained by selecting the optimal stimulation intensity and application site [ 16 , 17 ]. Differences in the shape of the stimulating coil can have a large effect on muscle contraction.…”

Factors Involved in Higher Knee Extension Torque Induced by Repetitive Peripheral Magnetic Stimulation

“…It has been reported that when the type of the coil is the same, the larger the coil size, the stronger the muscle contraction force is induced 13 . In the studies related to stimulation methods, it has been confirmed that strong muscle contraction could be obtained by correctly selecting the stimulation intensity and site 11,14 . Consequently, the effects of the type of equipment and stimulation method on the degree of muscle contraction have been clarified.…”

“…13 In the studies related to stimulation methods, it has been confirmed that strong muscle contraction could be obtained by correctly selecting the stimulation intensity and site. 11,14 Consequently, the effects of the type of equipment and stimulation method on the degree of muscle contraction have been clarified. However, the analysis of factors related to participant characteristics is still insufficient, and it has only been reported that muscle contraction induced by magnetic stimulation was weak in healthy participants with thicker subcutaneous fat.…”

Effect of Peripheral Magnetic Stimulation for Dysphagia Rehabilitation: A Systematic Review

“…However, recently, a device with a small coil for stimulating the suprahyoid muscle has been developed and applied. It has the potential to replace NMES, which has been considered as a therapeutic stimulation modality to improve reduced hyoid elevation [16].…”