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Updated: Jun 23, 2026
11:06
Bilateral Assessment of the Corticospinal Pathways of the Ankle Muscles Using Navigated Transcranial Magnetic Stimulation
Published on: February 19, 2019
Increases in corticospinal responsiveness during a sustained submaximal plantar flexion
B W Hoffman1, T Oya, T J Carroll
1School of Human Movement Studies, Univ. of Queensland, QLD 4072, Australia.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|May 16, 2009
Summary
Central nervous system fatigue involves changes in corticospinal excitability. This study found that during sustained muscle contractions, motor-evoked potentials (MEPs) increased, suggesting cortical processes contribute to altered responsiveness.
Area of Science:
- Neuroscience
- Human Physiology
- Motor Control
Background:
- Central nervous system (CNS) fatigue impacts motor performance.
- Understanding the site of CNS fatigue is crucial for optimizing training and rehabilitation.
- Corticospinal excitability changes during sustained contractions are not fully understood.
Purpose of the Study:
- To investigate changes in corticospinal responsiveness during sustained submaximal triceps surae contractions.
- To differentiate between cortical and subcortical contributions to altered excitability during fatigue.
- To determine the site of CNS fatigue during prolonged isometric contractions.
Main Methods:
- Participants performed sustained isometric contractions of the triceps surae at 30% maximal voluntary contraction (MVC) until task failure.
- Motor-evoked potentials (MEPs) and cervicomedullary motor-evoked potentials (CMEPs) were elicited by transcranial magnetic stimulation (TMS) of the motor cortex and cervicomedullary junction, respectively.
- Maximal M waves (M(max)) and superimposed twitches were measured to assess peripheral factors and maximal voluntary contraction.
Main Results:
- MEP amplitude significantly increased in soleus (113%) and medial gastrocnemius (108%) muscles during sustained contraction, reaching pre-fatigue MVC levels.
- CMEP amplitude increased in medial gastrocnemius (51%) but not soleus (63%), and at task failure, was significantly lower than during pre-fatigue MVC.
- These findings suggest that cortical excitability increases contribute significantly to the observed changes in corticospinal responsiveness during prolonged submaximal contractions.
Conclusions:
- Cortical processes play a substantial role in the increase of corticospinal responsiveness during sustained submaximal contractions of the triceps surae.
- Fatigue-related changes in corticospinal excitability are not uniform across all pathways or muscles.
- The findings provide insights into the neural mechanisms underlying central fatigue during prolonged muscle activity.
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