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

Abstract

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.

Fatigue in multiple sclerosis — A brief review

“…These findings suggest that mildly to moderately affected MS subjects can perform a fatiguing exercise requiring a high level of central motor control at the cost of greater strength loss and increased corticomotor excitability compared to control subjects [48]. In people without MS, functional magnetic resonance imaging (fMRI) studies show that during submaximal fatiguing exercises there is an increase in sensory processing and corticomotor drive to maintain task performance as fatigue develops [49]. Together, the studies discussed above suggest that in people with MS, the 'cost' of performing fatiguing motor tasks is increased loss of strength and increased cortex excitability in a wider cerebral area than in control subjects.…”

Basal ganglia are active during motor performance recovery after a demanding motor task

“…In the majority of these works, the motor task used to induce fatigue dealt with sustained or intermittent submaximal muscle contractions. Under this fatiguing condition, no change in cortical activity (Dettmers et al, 1996) or, otherwise, an increase in the activity of the primary motor cortex (M1) and premotor areas (Benwell et al, 2007;Liu et al, 2003;van Duinen et al, 2007) was observed.…”

“…In the literature, the experimental protocols designed to induce fatigue have been developed with the idea that exploring the limits of the motor system can provide insight as to how the system works, how it might break down during sustained activity and how the central nervous system might cope with deterioration in motor performance during a fatiguing exercise (Rodrigues et al, 2009). In particular, in several studies the effects of motor fatigue on human brain activity were studied with neuroimaging techniques (Benwell et al, 2007;Dettmers et al, 1996;Liu et al, 2003;Post et al, 2009;van Duinen et al, 2007). In the majority of these works, the motor task used to induce fatigue dealt with sustained or intermittent submaximal muscle contractions.…”

Voluntary activation and cortical activity during a sustained maximal contraction: An fMRI study

“…Several studies have investigated changes in brain activation during fatigue induced by a sustained or intermittent submaximal contraction [Benwell et al, 2007;Dettmers et al, 1996;Liu et al, 2003;van Duinen et al, 2007b]. The results of these studies were contradictory; one study showed no change in cortical activity [Dettmers et al, 1996] while the other three experiments showed an increase in activity of most motor areas [primary motor cortex, premotor areas: Benwell et al, 2007;Liu et al, 2003;van Duinen et al, 2007b].…”