Transcranial Magnetic Stimulation as a Tool to Study the Role of the Motor Cortex in Human Muscle Function

Avela, Janne; Grüber, Markus

doi:10.1002/9781444324822.ch8

Cited by 4 publications

(5 citation statements)

References 89 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Evidence of changes in corticospinal excitability has been inconsistent, with an increase (Griffin and Cafarelli 2007 ; Weier et al 2012 ), decrease (Carroll et al 2002 ; Beck et al 2007 ; Giboin et al 2018 ) or no change (Carroll et al 2009 ; Christie and Kamen 2014 ; Coombs et al 2016 ) shown following short-term resistance training. The differences in experimental designs, particularly as they relate to the training protocol, and the lack of agreement between the training and testing task (Avela and Gruber 2011 ; Kalmar 2018 ) likely contribute to these discrepancies. For example, whilst the majority of studies employed training intensities between 70 and 100% maximum intensity, these were a mixture of isometric (Griffin and Cafarelli 2007 ; Christie and Kamen 2014 ; Giboin et al 2018 ) and dynamic contractions (Carroll et al 2002 ; Beck et al 2007 ; Weier et al 2012 ; Coombs et al 2016 ).…”

Section: Cortical or Spinal Adaptations: Stimulation Studies Reveal Imentioning

confidence: 99%

The knowns and unknowns of neural adaptations to resistance training

et al. 2020

View full text Add to dashboard Cite

The initial increases in force production with resistance training are thought to be primarily underpinned by neural adaptations. This notion is firmly supported by evidence displaying motor unit adaptations following resistance training; however, the precise locus of neural adaptation remains elusive. The purpose of this review is to clarify and critically discuss the literature concerning the site(s) of putative neural adaptations to short-term resistance training. The proliferation of studies employing non-invasive stimulation techniques to investigate evoked responses have yielded variable results, but generally support the notion that resistance training alters intracortical inhibition. Nevertheless, methodological inconsistencies and the limitations of techniques, e.g. limited relation to behavioural outcomes and the inability to measure volitional muscle activity, preclude firm conclusions. Much of the literature has focused on the corticospinal tract; however, preliminary research in non-human primates suggests reticulospinal tract is a potential substrate for neural adaptations to resistance training, though human data is lacking due to methodological constraints. Recent advances in technology have provided substantial evidence of adaptations within a large motor unit population following resistance training. However, their activity represents the transformation of afferent and efferent inputs, making it challenging to establish the source of adaptation. Whilst much has been learned about the nature of neural adaptations to resistance training, the puzzle remains to be solved. Additional analyses of motoneuron firing during different training regimes or coupling with other methodologies (e.g., electroencephalography) may facilitate the estimation of the site(s) of neural adaptations to resistance training in the future.

show abstract

Section: Cortical or Spinal Adaptations: Stimulation Studies Reveal Imentioning

confidence: 99%

The knowns and unknowns of neural adaptations to resistance training

et al. 2020

View full text Add to dashboard Cite

show abstract

“…However, much like the issues highlighted by Sidhu et al. () and Avela and Gruber (), the evoked CNS responses in the aforementioned studies were recorded in single‐limb isometric knee extension, rather than the motor task (squat) performed during the intervention. If strength can be mediated by a neuroplastic response to a training stimulus, then the optimal method to assess the alterations in corticospinal and intracortical mechanisms of neuroplasticity might be during the motor task performed throughout the intervention.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, there has been an increase in the number of studies applying transcranial magnetic stimulation (TMS) in sport and exercise and movement sciences to assess intracortical and corticospinal activity in response to various interventions (Brownstein et al, and the testing modality used to detect changes in intracortical and corticospinal activity in response to the interventions. The discrepancy between intervention and testing modality has been highlighted previously by Avela and Gruber (2010), Sidhu, Cresswell, and Carroll (2013a) and, more recently, by Kalmar (2018), who suggested that future studies using TMS to assess neuromuscular responses to whole-body exercise should use testing modalities that more closely replicate the characteristics of the intervention. In support of this supposition, considerable evidence suggests that when assessing neuroplasticity after an intervention, the motor task performed for testing should mirror the motor task(s) performed during the intervention.…”

Section: Introductionmentioning

confidence: 99%

“…and Weier, Pearce, and Kidgell (2012) both showed alterations in CNS function after 4 weeks of heavy-load squat training, whereas Thomas et al (2017b) found no changes in corticospinal or intracortical activity when assessing the neuromuscular basis of acute performance enhancement in the minutes after a heavy-resistance squat protocol, despite inducing an increase in jump performance. However, much like the issues highlighted by Sidhu et al (2013a) and Avela and Gruber (2010), the evoked CNS responses in the aforementioned studies were recorded in single-limb isometric knee extension, rather than the motor task (squat) performed during the intervention. If strength can be mediated by a neuroplastic response to a training stimulus, then the optimal method to assess the alterations in corticospinal and intracortical mechanisms of neuroplasticity might be during the motor task performed throughout the intervention.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Motor cortical and corticospinal function differ during an isometric squat compared with isometric knee extension

Brownstein

Ansdell

Škarabot

et al. 2018

Experimental Physiology

View full text Add to dashboard Cite

It has been suggested that task-specific changes in neurophysiological function (neuroplasticity) should be assessed using testing modalities that replicate the characteristics of the intervention. The squat is a commonly prescribed resistance exercise that has been shown to elicit changes in CNS function. However, previous studies have assessed squat-induced neuroplasticity using isometric knee extension, potentially confounding the results. The aim of the present study was to assess the agreement between corticospinal and intracortical activity relating to the knee extensors during isometric knee extension compared with an isometric squat task. Eleven males completed a neurophysiological assessment in an isometric squat (IS) and knee-extension (KE) task matched for joint angles (hip, knee and ankle). Single- and paired-pulse transcranial magnetic stimulation was delivered during isometric contractions at a range of intensities to assess short-interval cortical inhibition (SICI) and corticospinal excitability. Group mean values for SICI (70 ± 14 versus 63 ± 12% of unconditioned motor evoked potential during IS and KE, respectively) and corticospinal excitability (mean differences 2-5% of the maximal compound muscle action potential at 25, 50, 75 and 100% maximal voluntary contraction between the IS and KE) were not different between the two tasks (P > 0.05) in the vastus lateralis. However, limits of agreement were wide, with poor-to-moderate average intraclass correlation coefficients (ICCs) (SICI, ICC = 0.15; corticospinal excitability, average ICC range = 0.0-0.63), indicating disparate corticospinal and intracortical activity between the IS and KE. These data highlight the importance of task specificity when assessing the modulation of corticospinal excitability and SICI in response to interventions resulting in neuroplastic changes.

show abstract

“…Specific to resistance training, when two distinct tasks are employed (ballistic vs. sustained contractions), neural adaptations are only demonstrated when the corticospinal tract is stimulated during the trained task (Giboin, Weiss, Thomas, & Gruber, 2018). The notion of utilising a task-specific testing task has been echoed throughout the past decade, with researchers highlighting the need to assess neurophysiological variables during the motor task used as in the intervention (Avela & Gruber, 2011;Kalmar, 2018;Sidhu, Cresswell, & Carroll, 2013). Despite the requirement for task-specific neural assessment, adaptation in response to lower-limb compound resistance training has not been assessed in a task-specific manner.…”

mentioning

confidence: 99%

Task‐specific strength increases after lower‐limb compound resistance training occurred in the absence of corticospinal changes in vastus lateralis

Ansdell

Brownstein

Škarabot

et al. 2020

Experimental Physiology

View full text Add to dashboard Cite

Neural adaptations subserving strength increases have been shown to be task-specific, but responses and adaptation to lower-limb compound exercises such as the squat are commonly assessed in a single-limb isometric task. This two-part study assessed neuromuscular responses to an acute bout (Study A) and 4 weeks (Study B) of squat resistance training at 80% of one-repetition-maximum, with measures taken during a task-specific isometric squat (IS) and non-specific isometric knee extension (KE). Eighteen healthy volunteers (25 ± 5 years) were randomised into either a training (n = 10) or a control (n = 8) group. Neural responses were evoked at the intracortical, corticospinal and spinal levels, and muscle thickness was assessed using ultrasound. The results of Study A showed that the acute bout of squat resistance training decreased maximum voluntary contraction (MVC) for up to 45 min post-exercise (−23%, P < 0.001). From 15-45 min post-exercise, spinally evoked responses were increased in both tasks (P = 0.008); however, no other evoked responses were affected (P ≥ 0.240). Study B demonstrated that following short-term resistance training, participants improved their one repetition maximum squat (+35%, P < 0.001), which was reflected by a task-specific increase in IS MVC (+49%, P = 0.001), but not KE (+1%, P = 0.882). However, no training-induced changes were observed in muscle thickness (P = 0.468) or any evoked responses (P = 0.141). Adjustments in spinal motoneuronal excitability are evident after acute resistance training. After a period of short-term training, there were no changes in the responses to central nervous system stimulation, which suggests that alterations in corticospinal properties of the vastus lateralis might not contribute to increases in strength.

show abstract

Transcranial Magnetic Stimulation as a Tool to Study the Role of the Motor Cortex in Human Muscle Function

Cited by 4 publications

References 89 publications

The knowns and unknowns of neural adaptations to resistance training

The knowns and unknowns of neural adaptations to resistance training

Motor cortical and corticospinal function differ during an isometric squat compared with isometric knee extension

Task‐specific strength increases after lower‐limb compound resistance training occurred in the absence of corticospinal changes in vastus lateralis

Contact Info

Product

Resources

About