Abstract: The aim of this study was to investigate spontaneous electromyographic activity of m. soleus in humans under conditions of simulated microgravity effects. To reproduce supportlessness, a ground based microgravity model, ―dry‖ immersion (DI), was used. Four volunteers (27.8±2.9 years old, height 179.0±4.0 cm, weight 74.0±3.7 kg) took part in the experiment. Electromyogram (EMG) recording was performed before DI, on the 1st, 3rd, 5th, 7th, 9th, 11th, 13th days of DI, as well as during the recovery period after its completion. EMG was recorded with disposable surface electrodes using NEUROSOFT (Russia) and ADInstruments (Australia) equipment (NEUROSOFT (Russia) and LabChart (Australia) software). During "dry" immersion, reliable changes in the maximum resting EMG amplitude were recorded in the soleus muscle. A decrease in maximum resting EMG amplitude was observed within the first hours of DI. During the following days, the parameter showed a further decline, reaching the most pronounced reduction by days 5 7, followed by stabilization below baseline (p≤0.05). During recovery, a tendency toward restoration to the baseline level was noted (p≤0.05). These results demonstrate that prolonged support withdrawal is associated with rapid but reversible changes in resting soleus EMG. In animal experiments, a number of authors noted that electromyographic activity in the soleus muscle resumes after about three days of functional unloading (Alfrod E.K. et al., 1987; De Doncker L., et al., 2005; Kawano F., et al., 2004; Shenkman et al., 2020). Preliminary results of our experiment did not reveal the development of a similar phenomenon in humans. Within the observation period, no development of a phenomenon analogous to the spontaneous EMG activity described in animal experiments was found. Thus, 14 day DI may serve as a useful model for investigating early neuromuscular responses of postural muscles to support withdrawal in humans, while resting soleus EMG may be considered a promising marker of adaptation during unloading and recovery. The study was supported by the Russian Science Foundation grant No. 24 15 00309.

Cite: Artamonova N.M.A. , Urbanskaya A.D. , Kitov V.V. , Rukavishnikov I.V. , Tomilovskaya E.S. , Shigueva T.A.
Tonic electromyographic activity of m. soleus at rest during 14-day support unloading
Международный симпозиум «Myology in the 21st Century», посвящѐнный 25-летию лаборатории миологии ГНЦ РФ – ИМБП РАН 03-05 Jun 2026