<b>The impact of high-frequency magnetic stimulation of peripheral nerves: muscle hardness, venous blood flow, and motor function of upper extremity in healthy </b><b>subjects </b>

Abstract

The purpose of this study was to investigate the impact of high-frequency peripheral nerve magnetic stimulation on the upper limb function. Twenty-five healthy adults (16 men and 9 women) participated in this study. The radial nerve of the non-dominant hand was stimulated by high-frequency magnetic stimulation device. A total of 600 impulses were applied at a frequency of 20 Hz and intensity of 1.2 resting motor threshold (rMT). At three time points (before, immediately after, and 15 min after stimulation), muscle hardness of the extensor digitorum muscle on the stimulated side was measured using a mechanical tissue hardness meter and a shear wave imaging device, cephalic venous blood flow on the stimulated side was measured using an ultrasound system, and the Box and Block test (BBT) was performed. Mechanical tissue hardness results did not show any significant differences between before, immediately after, and 15 min after stimulation. Measurements via shear wave imaging showed that muscle hardness significantly decreased both immediately and 15 min after stimulation compared to before stimulation (P < 0.05). Peripheral venous blood flow and BBT score significantly increased both immediately and 15 min after stimulation compared to before stimulation (P < 0.01). High-frequency peripheral nerve magnetic stimulation can achieve effects similar to electrical stimulation in a less invasive manner, and may therefore become an important element in next-generation rehabilitation.In a pathological state in which the muscle cannot contract voluntarily due to upper motor neuron disorders such as stroke and spinal cord injury, it is possible to contract the paralyzed muscle by directly applying electrical stimulation to the lower motor neuron and its innervating muscles (21). Functional electrical stimulation (FES) can be applied to such motor paralysis; specifically, using an FES system, targeted movements can be recovered by applying programmed movement stimuli to the paralyzed limb via multiple stimulation electrodes (22). Moreover, a recent report using fMRI demonstrated afferent effects in the motor cortex after FES (20), and FES is therefore anticipated for future development in the field of rehabilitation. The electrodes utilized in electrical stimulation are generally classified into surface electrodes or implanted electrodes. Some of the disadvantages of surface electrodes include: they induce pain and have risk of burn due to Joules heat caused by a concentration of current that is dependent on the non-uniform distribution of electrode contact impedance; they can only stimulate the shallow muscle layer and cannot selectively apply stimuli; and they require time for attachment and detachment (9). On

Effect of electrical stimulation on blood flow velocity and vessel size

“…On the other hand, blood flow velocity and vessel size influence circulatory function, and electrical stimulation also causes physiologic changes by activating sympathetic tone via muscle contraction [28]. In addition, electrical stimulation is effective at reducing the incidence of cardiac vein thrombus and the risk of pulmonary embolism [29] and increases venous return due to increased venous and muscular tension caused by sympathetic tone [30]. By the same electrophysiological mechanisms, high frequency-low intensity sensory stimulation induced vasoconstriction and increased blood flow velocity in this study; thus, it is thought that such stimulation could also enhance normal venous return.…”

Modulation of the Corticomotor Excitability by Repetitive Peripheral Magnetic Stimulation on the Median Nerve in Healthy Subjects

“…When rPMS is applied to the peripheral nerves, similar effects were also observed in healthy people. Using a pre-post design in normal subjects, Okudera et al (2015) applied 600 magnetic pulses at a frequency of 20 Hz on the radial nerve of the non-dominant hand and showed that the upper limb dexterity performance was improved, which was measured with the Box and Block Test, and this improvement was sustained for at least 15 min. For hand dexterity function change in the present study, the performance of the subjects for the Purdue pegboard improved after one session of rPNMS on the median nerve of the non-dominant hand, and this improvement was exhibited as a latent effect 24 h afterward.…”

Musculoskeletal Ultrasonography Assessment of Functional Magnetic Stimulation on the Effect of Glenohumeral Subluxation in Acute Poststroke Hemiplegic Patients

“…However, FES has some adverse reactions, for example, inducing pain, dermatitis, and even skin burns. In addition, the role of FES is very weak for the deep muscles and nerves, because its stimulating scope is shallow [ 26 , 27 ]. And FES is invalid in chronic hemiplegic patients.…”

“…A lot of researches have confirmed the effectiveness of FMS in the aspects of gastric emptying, neurogenic bowel, respiratory muscle conditioning, dysphagia, urinary incontinence, and so on [ 28 – 32 ]. Okudera et al have confirmed that FMS can improve upper limb motor function in healthy adults [ 27 ]. So we hypothesize that FMS may reduce GHS and promote the recovery of upper limb function in hemiplegic patients.…”