Cortical voluntary activation testing methodology impacts central fatigue

Mira, José A.; Lapole, Thomas; Souron, Robin; Messonnier, Laurent; Millet, Guillaume Y.; Rupp, Thomas

doi:10.1007/s00421-017-3678-x

Cited by 49 publications

(34 citation statements)

References 39 publications

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“…It is also worth noting that both LEPs and MEPs increased at a similar rate as shown previously (Maertens de Noordhout et al, 1992;Weavil et al, 2015) and peaked ≥75% and 50% in TA and RF, respectively, consistent with the relationship between motor unit recruitment and firing frequency of the muscles investigated (Gelli, Del Santo, Popa, Mazzocchio, & Rossi, 2007), which determines the probability of an evoked response (Bawa & Lemon, 1993;Brouwer, Ashby, & Midroni, 1989;Jones & Bawa, 1999). The lack of a decrease of evoked responses during MVC disagrees with some experiments (Goodall, Romer, & Ross, 2009;Mira et al, 2017), but corroborates others (Oya, Hoffman, & Cresswell, 2008;Weavil et al, 2015). This discrepancy has been attributed to the dependency of responses with increased contractions strength on stimulus intensity (Oya et al, 2008;Weavil et al, 2015), such that the greater the stimulus intensity, the lower the probability of an evoked response with increased firing rate (Matthews, 1999).…”

Section: Evidence For Stimulation Of Descending Tractssupporting

confidence: 77%

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Škarabot

Ansdell

Brownstein

et al. 2019

Eur J of Neuroscience

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Electrical stimulation over the mastoids or thoracic spinous processes has been used to assess subcortical contribution to corticospinal excitability, but responses are difficult to evoke in the resting lower limbs or are limited to only a few muscle groups. This might be mitigated by delivering the stimuli lower on the spinal column, where the descending tracts contain a greater relative density of motoneurons projecting to lower limb muscles. We investigated activation of the corticospinal axons innervating tibialis anterior (TA) and rectus femoris (RF) by applying a single electrical stimulus over the first lumbar spinous process (LS). LS was paired with transcranial magnetic stimulation (TMS) at interstimulus intervals (ISIs) of −16 (TMS before LS) to 14 ms (LS before TMS). The relationship between muscle contraction strength (10%–100% maximal) and the amplitude of single‐pulse TMS and LS responses was also investigated. Compared to the responses to TMS alone, responses to paired stimulation were significantly occluded in both muscles for ISIs ≥−8 ms (p ≤ 0.035), consistent with collision of descending volleys from TMS with antidromic volleys originating from LS. This suggests that TMS and LS activate some of the same corticospinal axons. Additionally, the amplitude of TMS and LS responses increased with increasing contraction strengths with no change in onset latency, suggesting responses to LS are evoked transsynaptically and have a monosynaptic component. Taken together, these experiments provide evidence that LS is an alternative method that could be used to discern segmental changes in the corticospinal tract when targeting lower limb muscles.

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Section: Evidence For Stimulation Of Descending Tractssupporting

confidence: 77%

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Škarabot

Ansdell

Brownstein

et al. 2019

Eur J of Neuroscience

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“…However, it is important to note that the exact time point of the start of the inhibitory mechanisms that explain SP and the beginning of the excitatory mechanisms reflected in the onset of MEP might not coincide. Nevertheless, a similar behaviour has been observed in previous studies (Girard, Bishop, & Racinais, 2013; Kirk, Trajano, Pulverenti, Rowe, & Blazevich, 2019; Latella, Hendy, Vanderwesthuizen, & Teo, 2018; Mira et al., 2017). We hypothesize that this suppression of inhibitory mechanisms might be the expression of a compensatory phenomenon to try to overcome a deficit of VA, which was observed throughout the fatiguing protocol and recovery.…”

Section: Discussionsupporting

confidence: 88%

Effects of caffeine on neuromuscular function in a non‐fatigued state and during fatiguing exercise

Mesquita

Cronin

Kyröläinen

et al. 2020

Experimental Physiology

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Caffeine enhances exercise performance, but its mechanisms of action remain unclear. In this study, we investigated its effects on neuromuscular function in a non-fatigued state and during fatiguing exercise. Eighteen men participated in this randomized, double-blind, placebo-controlled crossover trial. Baseline measures included plantarflexion force, drop jump, squat jump, voluntary activation of triceps surae muscle, soleus muscle contractile properties, M-wave, -motoneuron excitability (H-reflex), corticospinal excitability, short-interval intracortical inhibition, intracortical facilitation, silent period evoked by transcranial magnetic stimulation (SP) and plasma potassium and caffeine concentrations. Immediately after baseline testing, participants ingested caffeine (6 mg⋅kg −1 ) or placebo. After a 1-h rest, baseline measures were repeated, followed by a fatiguing stretch-shortening cycle exercise (sets of 40 bilateral rebound jumps on a sledge apparatus) until task failure. Neuromuscular testing was carried out throughout the fatigue protocol and afterwards. Caffeine enhanced drop jump height (by 4.2%) and decreased the SP (by 12.6%) in a non-fatigued state. A caffeine-related decrease in SP and short-interval intracortical inhibition before the fatiguing activity was associated with an increased time to task failure. The participants who benefitted from an improved performance on the caffeine day reported a significantly lower sense of effort during exercise and had an accelerated postexercise recovery of M-wave amplitude. Caffeine modulates inhibitory mechanisms of the CNS, recovery of M-wave amplitude and perception of effort. This study lays the groundwork for future examinations of differences in caffeine-induced neuromuscular changes between those who are deemed to benefit from caffeine ingestion and those who are not.

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“…By definition, the SP must be evoked during muscle contraction. Depending on the research question and study design, researchers have chosen to induce SPs at a wide range of contraction intensities, ranging from 10% (Goodall et al., ) to 100% MVC (Mira et al., ). Although previous data are equivocal regarding whether contraction intensity and the associated background EMG affect SP duration (Säisänen et al., ; Taylor, Allen, Butler, & Gandevia, ; Wilson et al., ), recent findings suggest the SP duration decreases with an increase in force output (Matsugi, ).…”

Section: Confounding Factors Influencing Interpretation Of the Silentmentioning

confidence: 99%

“…Depending on the research question and study design, researchers have chosen to induce SPs at a wide range of contraction intensities, ranging from 10% to 100% MVC (Mira et al, 2017). Although previous data are equivocal regarding whether contraction intensity and the associated background EMG affect SP duration (Säisänen et al, 2008;Taylor, Allen, Butler, & Gandevia, 1997;Wilson et al, 1993), recent findings suggest the SP duration decreases with an increase in force output (Matsugi, 2019 This is possibly attributable to a reduction in measurement error owing to clearer identification of SP offset with higher background EMG activity.…”

Section: Background Muscle Activity and Participant Instructionsmentioning

confidence: 99%

Myths and Methodologies: How loud is the story told by the transcranial magnetic stimulation‐evoked silent period?

Škarabot

Mesquita

Brownstein

et al. 2019

Experimental Physiology

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New Findings What is the topic of this review?The origin, interpretation and methodological constraints of the silent period induced by transcranial magnetic stimulation are reviewed. What advances does it highlight?The silent period is generated by both cortical and spinal mechanisms. Therefore, it seems inappropriate to preface silent period with ‘cortical’ unless additional measures are taken. Owing to many confounding variables, a standardized approach to the silent period measurement cannot be suggested. Rather, recommendations of best practice are provided based on the available evidence and the context of the research question. Abstract Transcranial magnetic stimulation (TMS) of the motor cortex evokes a response in the muscle that can be recorded via electromyography (EMG). One component of this response, when elicited during a voluntary contraction, is a period of EMG silence, termed the silent period (SP), which follows a motor evoked potential (MEP). Modulation of SP duration was long thought to reflect the degree of intracortical inhibition. However, the evidence presented in this review suggests that both cortical and spinal mechanisms contribute to generation of the SP, which makes prefacing SP with ‘cortical’ misleading. Further investigations with multi‐methodological approaches, such as TMS–EEG coupling or interaction of TMS with neuroactive drugs, are needed to make such inferences with greater confidence. A multitude of methodological factors can influence the SP and thus confound the interpretation of this measure; namely, background muscle activity, instructions given to the participant, stimulus intensity and the size of the MEP preceding the SP, and the approach to analysis. A systematic understanding of how the confounding factors influence the interpretation of SP is lacking, which makes standardization of the methodology difficult to conceptualize. Instead, the methodology should be guided through the lens of the research question and the population studied, ensuring greater reproducibility, repeatability and comparability of data sets. Recommendations are provided for the best practice within a given context of the experimental design.

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Cortical voluntary activation testing methodology impacts central fatigue

Abstract: After a 2-min sustained MVC, a few seconds of recovery change the amount of measured VA and associated parameters of central fatigue. The continuous method should be preferred to determine deficits in voluntary activation.

Cited by 49 publications

References 39 publications

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Effects of caffeine on neuromuscular function in a non‐fatigued state and during fatiguing exercise

Myths and Methodologies: How loud is the story told by the transcranial magnetic stimulation‐evoked silent period?

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