Reduction and Recovery of Self-sustained Muscle Activity After Fatiguing Plantar Flexor Contractions

Overview

Journal Eur J Appl Physiol

Specialty Physiology

Date 2024 Feb 10

PMID 38340155

Authors

Anthony J Blazevich

Ricardo N O Mesquita

Ronei S Pinto

Timothy Pulverenti

Sebastien Ratel

Affiliations

Soon will be listed here.

Abstract

Purpose: Persistent inward calcium and sodium currents (PICs) are crucial for initiation and maintenance of motoneuron firing, and thus muscular force. However, there is a lack of data describing the effects of fatiguing exercise on PIC activity in humans. We simultaneously applied tendon vibration and neuromuscular electrical stimulation (VibStim) before and after fatiguing exercise. VibStim induces self-sustained muscle activity that is proposed to result from PIC activation.

Methods: Twelve men performed 5-s maximal isometric plantar flexor contractions (MVC) with 5-s rests until joint torque was reduced to 70%MVC. VibStim trials consisted of five 2-s trains of neuromuscular electrical stimulation (20 Hz, evoking 10% MVC) of triceps surae with simultaneous Achilles tendon vibration (115 Hz) without voluntary muscle activation. VibStim was applied before (PRE), immediately (POST), 5-min (POST-5), and 10-min (POST-10) after exercise completion.

Results: Sustained torque (T) and soleus electromyogram amplitudes (EMG) measured 3 s after VibStim were reduced (T: -59.0%, p < 0.001; soleus EMG: -38.4%, p < 0.001) but largely recovered by POST-5, and changes in MVC and T were correlated across the four time points (r = 0.69; p < 0.001). After normalisation to values obtained at the end of the vibration phase to control for changes in fibre-specific force and EMG signal characteristics, decreases in T (-42.9%) and soleus EMG (-22.6%) remained significant and were each correlated with loss and recovery of MVC (r = 0.41 and 0.46, respectively).

Conclusion: The parallel changes observed in evoked self-sustained muscle activity and force generation capacity provide motivation for future examinations on the potential influence of fatigue-induced PIC changes on motoneuron output.

References

Blazevich A, Babault N . Post-activation Potentiation Versus Post-activation Performance Enhancement in Humans: Historical Perspective, Underlying Mechanisms, and Current Issues. Front Physiol. 2019; 10:1359. PMC: 6838751. DOI: 10.3389/fphys.2019.01359. View

Mesquita R, Taylor J, Trajano G, Skarabot J, Holobar A, Goncalves B . Effects of reciprocal inhibition and whole-body relaxation on persistent inward currents estimated by two different methods. J Physiol. 2022; 600(11):2765-2787. PMC: 9325475. DOI: 10.1113/JP282765. View

Bellardita C, Caggiano V, Leiras R, Caldeira V, Fuchs A, Bouvier J . Spatiotemporal correlation of spinal network dynamics underlying spasms in chronic spinalized mice. Elife. 2017; 6. PMC: 5332159. DOI: 10.7554/eLife.23011. View

Trajano G, Taylor J, Orssatto L, McNulty C, Blazevich A . Passive muscle stretching reduces estimates of persistent inward current strength in soleus motor units. J Exp Biol. 2020; 223(Pt 21). DOI: 10.1242/jeb.229922. View

Novacheck . The biomechanics of running. Gait Posture. 1999; 7(1):77-95. DOI: 10.1016/s0966-6362(97)00038-6. View

Bochkezanian V, Newton R, Trajano G, Vieira A, Pulverenti T, Blazevich A . Effect of tendon vibration during wide-pulse neuromuscular electrical stimulation (NMES) on muscle force production in people with spinal cord injury (SCI). BMC Neurol. 2018; 18(1):17. PMC: 5809925. DOI: 10.1186/s12883-018-1020-9. View

Orssatto L, Fernandes G, Blazevich A, Trajano G . Facilitation-inhibition control of motor neuronal persistent inward currents in young and older adults. J Physiol. 2022; 600(23):5101-5117. PMC: 10092053. DOI: 10.1113/JP283708. View

Binder M, Powers R, Heckman C . Nonlinear Input-Output Functions of Motoneurons. Physiology (Bethesda). 2019; 35(1):31-39. PMC: 7132324. DOI: 10.1152/physiol.00026.2019. View

Kavanagh J, McFarland A, Taylor J . Enhanced availability of serotonin increases activation of unfatigued muscle but exacerbates central fatigue during prolonged sustained contractions. J Physiol. 2018; 597(1):319-332. PMC: 6312415. DOI: 10.1113/JP277148. View

10.

Cotel F, Exley R, Cragg S, Perrier J . Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation. Proc Natl Acad Sci U S A. 2013; 110(12):4774-9. PMC: 3607056. DOI: 10.1073/pnas.1216150110. View

11.

Udina E, DAmico J, Bergquist A, Gorassini M . Amphetamine increases persistent inward currents in human motoneurons estimated from paired motor-unit activity. J Neurophysiol. 2010; 103(3):1295-303. PMC: 2887628. DOI: 10.1152/jn.00734.2009. View

12.

Mesquita R, Taylor J, Trajano G, Holobar A, Goncalves B, Blazevich A . Effects of jaw clenching and mental stress on persistent inward currents estimated by two different methods. Eur J Neurosci. 2023; 58(9):4011-4033. DOI: 10.1111/ejn.16158. View

13.

GREGORY J, Mark R, Morgan D, Patak A, Polus B, Proske U . Effects of muscle history on the stretch reflex in cat and man. J Physiol. 1990; 424:93-107. PMC: 1189803. DOI: 10.1113/jphysiol.1990.sp018057. View

14.

Cannavan D, Coleman D, Blazevich A . Lack of effect of moderate-duration static stretching on plantar flexor force production and series compliance. Clin Biomech (Bristol). 2011; 27(3):306-12. DOI: 10.1016/j.clinbiomech.2011.10.003. View

15.

Farina D, Zennaro D, Pozzo M, Merletti R, Laubli T . Single motor unit and spectral surface EMG analysis during low-force, sustained contractions of the upper trapezius muscle. Eur J Appl Physiol. 2004; 96(2):157-64. DOI: 10.1007/s00421-004-1261-8. View

16.

Magalhaes F, de Toledo D, Kohn A . Plantar flexion force induced by amplitude-modulated tendon vibration and associated soleus V/F-waves as an evidence of a centrally-mediated mechanism contributing to extra torque generation in humans. J Neuroeng Rehabil. 2013; 10:32. PMC: 3621298. DOI: 10.1186/1743-0003-10-32. View

17.

Keenan K, Farina D, Maluf K, Merletti R, Enoka R . Influence of amplitude cancellation on the simulated surface electromyogram. J Appl Physiol (1985). 2004; 98(1):120-31. DOI: 10.1152/japplphysiol.00894.2004. View

18.

Hounsgaard J, Hultborn H, Jespersen B, Kiehn O . Bistability of alpha-motoneurones in the decerebrate cat and in the acute spinal cat after intravenous 5-hydroxytryptophan. J Physiol. 1988; 405:345-67. PMC: 1190979. DOI: 10.1113/jphysiol.1988.sp017336. View

19.

Heckman C, Johnson M, Mottram C, Schuster J . Persistent inward currents in spinal motoneurons and their influence on human motoneuron firing patterns. Neuroscientist. 2008; 14(3):264-75. PMC: 3326417. DOI: 10.1177/1073858408314986. View

20.

Lee R, Heckman C . Bistability in spinal motoneurons in vivo: systematic variations in persistent inward currents. J Neurophysiol. 1998; 80(2):583-93. DOI: 10.1152/jn.1998.80.2.583. View