Temporal dynamics of muscle, spinal and cortical excitability and their association with kinematics during three minutes of maximal-rate finger tapping

Elena Madinabeitia-Mancebo,Javier Cudeiro,Pablo Arias,Antonio Madrid,Amalia Jácome

doi:10.1038/s41598-020-60043-0

Elena Madinabeitia-Mancebo, Javier Cudeiro + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-60043-0

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Abstract

We tested peripheral, spinal and cortical excitability during 3 minutes of unresisted finger tapping at the maximal possible rate, which induced fatigue. Subsequently, we studied the temporal dynamics of muscle fatigue, expressed in the tapping movement profile, and its relationship to neural systems using mixed model analyses. The tapping rate decreased by 40% over the duration of the task. The change in the amplitude of the range of motion was not significant. The excitability of the flexor and extensor muscles of the index finger was tested via evoked potentials obtained with various types of stimulation at various levels of the motor system. The change in spinal excitability with time was evaluated considering the simultaneous changes in muscle excitability; we also considered how spinal excitability changed over time to evaluate cortical excitability. Excitability in the flexor and extensor muscles at the different levels tested changed significantly, but similar excitability levels were observed at notably different tapping rates. Our results showed that only 33% of the decrease in the tapping rate was explained by changes in the excitability of the structures tested in the present work.

Highlights

IntroductionThe magnitude of the change in compound muscle action potentials (CMAPs) was discrete, the CMAPs decreased significantly along the ft task (p < 0.001) (Fig. 6a,b)
The four participants who withdrew from the study refused to participate in the session that included compound muscle action potentials (CMAPs) and cervicomedullary evoked potentials (CMEPs) testing due to the discomfort produced by these types of stimulation
Associations between changes in excitability and motor behaviour during the task. These analyses show whether muscular excitability and neuromuscular transmission (CMAP), spinal excitability (CMEP/ CMAP) and cortical excitability (MEP/CMEP and MEPc/motor evoked potentials (MEPs)) explain changes in ft behaviour

Summary

Introduction

The magnitude of the change in CMAPs was discrete, the CMAPs decreased significantly along the ft task (p < 0.001) (Fig. 6a,b). The ratio changed during execution of the task (p < 0.001), increasing for the first 30–40 s and remaining relatively stable. The change in the MEP/CMEP ratio with ft was small in magnitude but statistically significant (p < 0.001)

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