Abstract
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.
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Acknowledgments
We are grateful to Dr. Vincent Low (Head) and radiographers at the MRI unit, Department of Radiology, Sir Charles Gairdner Hospital, for their support and assistance in carrying out these studies. Peter Clissa and Peter Proctor from the School of Psychology, University of Western Australia, are thanked for the design and construction of the handgrip device used in this study. This study was supported by the Neuromuscular Foundation of Western Australia. NMB is a recipient of an Australian Postgraduate Award, Jean Rogerson Postgraduate Scholarship and 2004 Woodside Neurotrauma PhD Excellence Award.
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Benwell, N.M., Mastaglia, F.L. & Thickbroom, G.W. Reduced functional activation after fatiguing exercise is not confined to primary motor areas. Exp Brain Res 175, 575–583 (2006). https://doi.org/10.1007/s00221-006-0573-9
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DOI: https://doi.org/10.1007/s00221-006-0573-9