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SPECIAL SECTION RELATED PAPERS |
1 University of Wisconsin Medical School, John Rankin Laboratory of Pulmonary Medicine, Madison, WI, USA
We asked whether the central effects of fatiguing locomotor muscle fatigue exert an inhibitory influence on central motor drive to regulate the total degree of peripheral fatigue development. Eight cyclists performed constant-workload prefatigue trials (a) to exhaustion (83% of peak power output (Wpeak), 10 ± 1 min; PFT83%), and (b) for an identical duration but at 67% Wpeak (PFT67%). Exercise-induced peripheral quadriceps fatigue was assessed via changes in potentiated quadriceps twitch force (
Qtw,pot) from pre- to post-exercise in response to supra-maximal femoral nerve stimulation (Qtw,pot). On different days, each subject randomly performed three 5 km time trials (TTs). First, subjects repeated PFT83% and the TT was started 4 min later with a known level of pre-existing locomotor muscle fatigue (Qtw,pot –36%) (PFT83%-TT). Second, subjects repeated PFT67% and the TT was started 4 min later with a known level of pre-existing locomotor muscle fatigue (Qtw,pot –20%) (PFT67%-TT). Finally, a control TT was performed without any pre-existing level of fatigue. Central neural drive during the three TTs was estimated via quadriceps EMG. Increases in pre-existing locomotor muscle fatigue from control TT to PFT83%-TT resulted in significant dose-dependent changes in central motor drive (–23%), power output (–14%), and performance time (+6%) during the TTs. However, the magnitude of locomotor muscle fatigue following various TTs was not different (Qtw,pot of –35 to –37%, P = 0.35). We suggest that feedback from fatiguing muscle plays an important role in the determination of central motor drive and force output, so that the development of peripheral muscle fatigue is confined to a certain level.
(Received 30 July 2007;
accepted after revision 23 October 2007;
first published online 25 October 2007)
Corresponding author M. Amann: The John Rankin Laboratory of Pulmonary Medicine, 4245 Medical Science Center, 1300 University Avenue, Madison, WI 53706, USA. Email: amann{at}wisc.edu
This article has been cited by other articles:
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 M. Amann, S. M. Marcora, L. Nybo, T. A. Duhamel, T. D. Noakes, V. Jaquinandi, J. L. Saumet, P. Abraham, B. T. Ameredes, M. Burnley, et al. Viewpoint: Fatigue mechanisms determining exercise performance: integrative physiology is systems physiology. J Appl Physiol, May 1, 2008; 104(5): 1543 - 1544. [Full Text] [PDF]
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M. Amann and J. A. Dempsey Reply from Markus Amann and Jerome A. Dempsey J. Physiol., April 1, 2008; 586(7): 2029 - 2030. [Full Text] [PDF]
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 S. M. Marcora, A. Bosio, and H. M. de Morree Locomotor muscle fatigue increases cardiorespiratory responses and reduces performance during intense cycling exercise independently from metabolic stress Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2008; 294(3): R874 - R883. [Abstract] [Full Text] [PDF]
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M. Amann, L. M. Romer, and J. A. Dempsey Reply from Markus Amann, Lee M. Romer and Jerome A. Dempsey J. Physiol., December 15, 2007; 585(3): 923 - 924. [Full Text] [PDF]
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