Brain-imaging during an isometric leg extension task at graded intensities

Abstract

Imaging the brain during complex and intensive movements is challenging due to the susceptibility of brain-imaging methods for motion and myogenic artifacts. A few studies measured brain activity during either single-joint or low-intensity exercises; however, the cortical activation state during larger movements with increases up to maximal intensity has barely been investigated so far. Eleven right-handed volunteers (22–45 years in age) performed isometric leg extensions with their right leg at 20, 40, 60, 80, and 100% of their maximal voluntary contraction. Contractions were hold for 20 s respectively. Electroencephalographic (EEG) and electromyographic (EMG) activity was recorded. Standardized low-resolution brain electromagnetic tomography (sLORETA) was used to localize the cortical current density within the premotor (PMC), primary motor (M1), primary somatosensory (S1) and somatosensory association cortex (SAC). ANOVA was used for repeated measures for comparison of intensities and between the left and right hemispheres. The quality of the EEG signal was satisfying up to 80% intensity. At 100% half of the participants were not able to keep their neck and face muscles relaxed, leading to myogenic artifacts. Higher contralateral vs. ipsilateral hemispheric activity was found for the S1, SAC and, PMC. M1 possessed higher ipsilateral activity. The highest activity was localized in the M1, followed by S1, PMC, and SAC. EMG activity and cortical current density within the M1 increased with exercise intensity. EEG recordings during bigger movements up to submaximal intensity (80%) are possible, but maximal intensities are still hard to investigate when subjects contracted their neck and face muscles at the same time. Isometric contractions mainly involve the M1, whereas the S1, PMC, and SAC seem not to be involved in the force output. Limitations and recommendations for future studies are discussed.

Fatigue in Chronic Respiratory Diseases: Theoretical Framework and Implications For Real-Life Performance and Rehabilitation

“…This could be achieved by augmenting neurostimulation techniques (e.g., TMS) with neuroimaging (e.g., multichannel functional near-infrared spectroscopy) and corticomuscular coherence (EEG-EMG coupling) methods. These non-invasive techniques all demonstrated good feasibility during isometric contractions in both healthy and pathological conditions and can detect small changes in brain activity with fatigue (Ushiyama et al, 2011 ; Gwin and Ferris, 2012 ; Abeln et al, 2013 ; Perrey, 2013 ; Alexandre et al, 2014 ; Cremoux et al, 2017 ; Marillier et al, 2018a ). Such techniques could thus be implemented in the future during local exercises such as the QIF test, in various CRD populations.…”

Editorial: Investigating the human brain and muscle coupling during whole-body challenging exercise

“…Advances in functional neuroimaging techniques of the human brain with behavioral outcomes, such as electroencephalography (EEG) and near-infrared spectroscopy (NIRS), helped to generate first valuable data in human exercise research. Increased muscle recruitment as revealed by electromyographic activity was accompanied by a higher brain cortical activity (measured by EEG) localized mainly in the primary motor cortices during unilateral isometric knee extensions (Abeln et al, 2013 ). This bilateral activation of motor cortex observed also in NIRS study (Derosière et al, 2014 ) during graded unimanual force production may be caused by the occurrence of interhemispheric inhibition (i.e., mirror activity of the passive limb during unilateral movement).…”

Brain activation differences between muscle actions for strength and fatigue: A brief review.

“…Understanding how the brain functions and how it controls strength and fatigue levels during exercise has been a topic of interest in past years [1][2][3][4][5][6][7][8][9][10][11][12] . Studies exploring which cortical regions are more activated during specific types of muscle actions have been important for improvements in performance and rehabilitation of movement disorders 1 .…”

“…Primary and supplementary motor cortex activity during fine motor strength and fatigue have been previously described as principally depending on dexterous control and task specificity, especially in finger and hand grip strength [18][19][20][21][22][23] . However, to date, only a few studies have reported cortical activation patterns during more demanding and intense activities 1,[5][6][7]10 . How the brain is activated differently between concentric, eccentric and isometric muscle actions during high intensity performance tasks is less well understood.…”