Reduced functional activation after fatiguing exercise is not confined to primary motor areas.
We have previously shown that following a period of unimanual fatiguing exercise, there is a reduction in primary sensorimotor cortex (SM1) activation with movement of either the fatigued or the non-fatigued hand by Benwell et al. (Exp Brain Res 167:160-164, 2005). In the present study we have investigated whether this reduction is confined to motor areas or is more widespread. Functional imaging was performed before and after a 10-minute fatiguing exercise of the left hand (30% of maximum handgrip strength) in seven normal subjects (4 M, mean age 25 years). The activating task was a handgrip against a low resistance (1 kg) in response to a visual cue (chequerboard reversal every 2 +/- 0.5 s). We compared activation in SM1, supplementary motor area (SMA), cerebellum (CB) and primary visual cortex (V1) before and after the fatiguing exercise. After exercise, contralateral SM1 activation was reduced by 33% (P < 0.05) compared to baseline for the fatigued hand and by 49% for the non-fatigued hand (P < 0.05). A similar pattern was seen for the bilateral SMA and ipsilateral CB following exercise (45 vs. 50% for SMA; 30 vs. 35% for CB; fatigued versus non-fatigued). Activation was also reduced in V1 but to a lesser extent than in motor areas (19 vs. 24%; fatigued versus non-fatigued). These results show that although the reduced functional activation during the recovery period after fatiguing exercise is more marked in motor areas, it also extends to non-motor areas such as the visual cortex, suggesting that there are more widespread changes in cerebral haemodynamic responses after fatigue.
Benwell
Nicola M
NM
Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA 6009, Australia. nbenwell@cyllene.uwa.edu.au
Mastaglia
Frank L
FL
Thickbroom
Gary W
GW
D000328:Adult; D001931:Brain Mapping; D002531:Cerebellum / Q000033:anatomy & histology / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015536:Down-Regulation / Q000502:physiology; D019054:Evoked Potentials, Motor / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000033:anatomy & histology / Q000502:physiology; D006225:Hand / Q000294:innervation / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology*; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*