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

BACKGROUND: Brain activation differences for strength and fatigue have recently been investigated due to advancements in brain-imaging methods. AIM: To review brain activation differences between concentric, eccentric and isometric muscle actions for strength and fatigue.  METHODS : 12 studies were selected by accessing PubMed and Web of Knowledge databases. RESULTS: Collectively, the literature demonstrates that for strength the parietal and frontal lobes of the cortex that control movement preparation, planning and execution, and process feedback information are more activated during eccentric than concentric actions. In the supplementary motor area, event-related desynchronization is continued for both concentric and eccentric actions, but only present at the beginning and end of isometric actions. This indicates the CNS specifically controls each of these muscle actions. For fatigue, cortical activation is greater in the supplementary and premotor areas during isometric actions, but may be greater primarily in the central, occipital and parietal cortical areas for concentric and eccentric actions. INTERPRETATION: Muscular strength can be elicited with eccentric actions to more effectively activate control and memory of movement in the parietal and frontal lobes. Muscular fatigue can be elicited with isometric actions to selectively activate supplementary and premotor areas, or with concentric and eccentric actions for central, occipital and parietal cortical areas.