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This Article Full Text Full Text (PDF) All Versions of this Article: 92/2/417    most recent expphysiol.2006.035972v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ross, E. Z. Articles by Nowicky, A. Search for Related Content PubMed PubMed Citation Articles by Ross, E. Z. Articles by Nowicky, A. Related Collections Heart/Cardiac Muscle

¹ Centre for Sports Medicine and Human Performance³ School of Health Sciences, Brunel University, Uxbridge, Middlesex, UK ² Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, UK

It is unknown whether changes in corticomotor excitability follow prolonged exercise in healthy humans. Furthermore, the role of supraspinal fatigue in decrements of force production and voluntary activation following prolonged exercise has not been established. This study investigated peripheral and central fatigue after a marathon (42.2 km) on a treadmill. Isometric ankle dorsiflexion force and electromyographic responses of the tibialis anterior in response to magnetic stimulation of the peroneal nerve (PNMS) and the motor cortex (TMS) were measured before, immediately after, 4 and 24 h post-marathon (MAR) in nine volunteers (mean ± S.D. completion time, 208 ± 22 min). Maximal voluntary contraction decreased by 18 ± 7% immediately after MAR (P = 0.009) and remained significantly decreased after 4 h. The amplitude of the evoked response to TMS, but not to PNMS, was depressed immediately post-MAR by 57 ± 25% (P = 0.04). Potentiated resting twitch force was reduced in response to both TMS and PNMS post-MAR (71 ± 8 and 35 ± 2% decrease, P = 0.035 and 0.037, respectively), and voluntary activation was reduced to 61.9 ± 18% immediately post-MAR (P < 0.05). All measures had returned to baseline values after 24 h. These results suggest that fatigue was attributable to both a disturbance of the contractile apparatus within the muscle and submaximal output from the motor cortex.

(Received 29 September 2006; accepted after revision 9 November 2006; first published online 10 November 2006)
Corresponding author E. Ross: Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK. Email: emma.Ross{at}brunel.ac.uk

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