Examining neuromuscular modulation using repetitive peripheral magnetic stimulation -The location of repetitive peripheral nerve stimulation influence soleus H-reflex-

Kazunori Morozumi, Yohei Masugi, Michio Tojima, Katsuyuki Morishita, Takashi Inomata
Purpose:

　This study aimed to investigate the effect of rPMS on monosynaptic reflex in the soleus muscle and whether the effect of rPMS depends on the location of the stimulation.

Methods:

　We recruited 36 males (age, 20.1 ± 1.1 years; height, 171.8 ± 5.7 cm; body weight, 64.5 ± 6.8 kg). These participants were randomly divided into three groups: rPMS at the tibial nerve (NS, n=12), rPMS at the soleus motor point on the muscle belly (MS, n=12), and control (C, n=12, no rPMS).

　First, the H-reflex recruitment curve was measured using electrical stimulation with a pulse width of 1 ms on the right tibial nerve to decide the stimulation intensity.  The stimulation intensity eliciting 60% of the maximum H-reflex amplitude was used for the test stimulation for H-reflex measurement before and after rPMS.

　A magnetic stimulation system (Pathleader, IFG Corporation) delivered rPMS for 10 min at a pulse width of 350 µs, frequency of 50 Hz, stimulation intensity of 70% (maximum magnetic flux density 0.85-0.94T), stimulation duration of 2 s, and rest duration of 8 s.

　The H-reflex was measured 24 times over 2 min at a frequency of 0.2 Hz before and after the intervention, as well as before and after 10 min of control rest in the prone positions. The data of the 12 measurements in the second minute were used for the analysis.

　A two-way analysis of variance (ANOVA) was used to analyze H-wave amplitude before and after the intervention in each group, followed by post-hoc paired t-tests with Bonferroni correction (p = 0.05).


Results:

　The ANOVA revealed significant time*group interaction (p0.05). Post-hoc testing showed that H-reflex amplitude increased after rPMS in the NS group (mean value ±S.D:  pre 2.4 ± 0.9 mV vs post 3.1 ± 1.4 mV, p=0.003), but not in the MS (mean value ±S.D:pre 2.52± 1.23 mV vs post 2.46± 1.22 mV, p= 1.92) and control (mean value ±S.D:pre 2.17± 1.54 mV vs post 2.44± 1.77 mV, p=0.36). 



Conclusion(s):

　The changes in H-reflex amplitude after rPMS observed in the NS group may be explained by the possibility that direct nerve stimulation excite I-a sensory fibers, facilitating motor neuron pools via synapses in the spinal cord.




Implications:

　If the facilitative effect of rPMS on the excitability of monosynaptic reflex is expected, the stimulation of peripheral nerves could be more effective than muscle belly stimulation.


Funding acknowledgements:
This research was adopted by the JSPS Grant-in-Aid for Scientific Research C in Japan in April 2023 (Project Number: 23K10485)
Keywords:
Repetitive peripheral magnetic stimulation
soleus Hoffmann reflex
magnetic stimulation area
Primary topic:
Neurology
Second topic:
Disability and rehabilitation
Third topic:
Other
Did this work require ethics approval?:
Yes
Name the institution and ethics committee that approved your work:
Institution: Tokyo International University Ethics committee: Tokyo International University’s Committee of Ethics
Provide the ethics approval number:
Ethical Approval Number: No. 23-3
Has any of this material been/due to be published or presented at another national or international conference prior to the World Physiotherapy Congress 2025?:
No

Back to the listing