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Neuroscience. 2016 Jun 21;326:95-104. doi: 10.1016/j.neuroscience.2016.03.060. Epub 2016 Apr 4.

Post-exercise depression following submaximal and maximal isometric voluntary contraction.

Author information

1
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States; School of Biomedical Sciences, Kent State University, Kent, OH, United States.
2
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
3
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States; Center for Neurological Restoration, Neurosurgery, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States.
4
Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, OH, United States.
5
Human Performance & Engineering Research, Kessler Foundation, West Orange, NJ, United States; Department of Physical Medicine & Rehab, Rutgers New Jersey Medical School, Rutgers University, Newark, NJ, United States. Electronic address: Gyue@kesslerfoundation.org.
6
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States; Center for Neurological Restoration, Neurosurgery, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States; Department of Physical Medicine & Rehab, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States. Electronic address: plowe2@ccf.org.

Abstract

It is well known that corticomotor excitability is altered during the post-exercise depression following fatigue within the primary motor cortex (M1). However, it is currently unknown whether corticomotor reorganization following muscle fatigue differs between magnitudes of force and whether corticomotor reorganization occurs measured with transcranial magnetic stimulation (TMS). Fifteen young healthy adults (age 23.8±1.4, 8 females) participated in a within-subjects, repeated measures design study, where they underwent three testing sessions separated by one-week each. Subjects performed separate sessions of each: low-force isometric contraction (30% maximal voluntary contraction [MVC]), high-force isometric contraction (95% MVC) of the first dorsal interosseous (FDI) muscle until self-perceived exhaustion, as well as one session of a 30-min rest as a control. We examined changes in corticomotor map area, excitability and location of the FDI representation in and around M1 using TMS. The main finding was that following low-force, but not high-force fatigue (HFF) corticomotor map area and excitability reduced [by 3cm(2) (t(14)=-2.94, p=0.01) and 56% respectively t(14)=-4.01, p<0.001)]. Additionally, the region of corticomotor excitability shifted posteriorly (6.4±2.5mm) (t(14)=-6.33, p=.019). Corticomotor output became less excitable particularly in regions adjoining M1. Overall, post-exercise depression is present in low-force, but not for HFF. Further, low-force fatigue (LFF) results in a posterior shift in corticomotor output. These changes may be indicative of increased sensory feedback from the somatosensory cortex during the recovery phase of fatigue.

KEYWORDS:

fatigue; healthy; isometric contraction; post-exercise depression; primary motor cortex; transcranial magnetic stimulation

[Indexed for MEDLINE]

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