Document Type

Journal Article

Publication Title

Journal of Physiology

Publisher

Wiley

School

School of Medical and Health Sciences

RAS ID

51966

Funders

Versus Arthritis Foundation Fellowship, Slovenian Research Agency (project J2-1731 and Programme funding P2-0041).

Comments

Mesquita, R. N., Taylor, J. L., Trajano, G. S., Škarabot, J., Holobar, A., Gonçalves, B. A., & Blazevich, A. J. (2022). Effects of reciprocal inhibition and whole‐body relaxation on persistent inward currents estimated by two different methods. The Journal of Physiology. Advanced online Publication. https://doi.org/10.1113/JP282765

Abstract

Persistent inward currents (PICs) are crucial for initiation, acceleration, and maintenance of motoneuron firing. As PICs are highly sensitive to synaptic inhibition and facilitated by serotonin and noradrenaline, we hypothesised that both reciprocal inhibition (RI) induced by antagonist nerve stimulation and whole-bodyrelaxation (WBR) would reduce PICs in humans. To test this, we estimated PICs using the well-established paired motor unit (MU) technique. High-density surface electromyograms were recorded from gastrocnemius medialis during voluntary, isometric 20-s ramp, plantarflexor contractions and decomposed into MU discharges to calculate delta frequency (ΔF). Moreover, another technique (VibStim), which evokes involuntary contractions proposed to result from PIC activation, was used. Plantarflexiontorque and soleus activity were recorded during 33-s Achilles tendon vibration and simultaneous 20-Hz bouts of neuromuscular electrical stimulation (NMES) of triceps surae. ΔF was decreased by RI (n=15, 5 females) and WBR (n=15, 7 females). In VibStim, torque during vibration at the end of NMES and sustained post-vibration torque were reduced by WBR (n=19, 10 females), while other variables remained unchanged. All VibStim variables remained unaltered in RI (n=20, 10 females). Analysis of multiple human MUs in this study demonstrates the ability of local, focused inhibition to attenuate the effects of PICs onmotoneuron output during voluntary motor control. Moreover, it shows the potential to reduce PICs through non-pharmacological, neuromodulatory interventions such as WBR. The absence of a consistent effect in VibStim might be explained by a floor effect resulting from low-magnitude involuntary torque combined with the negative effects of the interventions.

DOI

10.1113/JP282765

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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