Changes in the functional MR signal in motor and non-motor areas during intermittent fatiguing hand exercise.

The aim of this study was to determine whether there were significant changes in the time course of the functional magnetic resonance imaging (fMRI) signal in motor and non-motor regions of both cerebral hemispheres during a unilateral fatiguing exercise of the hand. Twelve subjects performed a submaximal (30%) intermittent fatiguing handgrip exercise (3 s grip, 2 s release, left hand) for approximately 9 min during fMRI scanning. Regression analysis was used to measure changes in fMRI signal from primary sensorimotor cortex (SM1), premotor cortex and visual cortex (V1) in both hemispheres. Force declined to 77 +/- 3.6% of prefatigue maximal force (P < 0.05). The fMRI signal from SM1 contralateral to the fatiguing hand increased by 1.2 +/- 0.5% of baseline (P < 0.05). The fMRI signal from the ipsilateral SM1 did not change significantly. Premotor cortex showed a similar pattern but did not reach significance. The signal from V1 increased significantly for both hemispheres (contralateral 1.3 +/- 0.9%, ipsilateral 1.5 +/- 0.9% of baseline and P < 0.05). During the performance of a unimanual, submaximal fatiguing exercise there is an increase in activation of motor and non-motor regions. The results are in keeping with the notion of an increase in sensory processing and corticomotor drive during fatiguing exercise to maintain task performance as fatigue develops.