title: Reduced muscle activation during exercise related to brain oxygenation and metabolism in humans.
abstract: Maximal exercise may be limited by central fatigue defined as an inability of the central nervous system to fully recruit the involved muscles. This study evaluated whether a reduction in the cerebral oxygen-to-carbohydrate index (OCI) and in the cerebral mitochondrial oxygen tension relate to the ability to generate a maximal voluntary contraction and to the transcranial magnetic stimulated force generation. To determine the role of a reduced OCI and in central fatigue, 16 males performed low intensity, maximal intensity and hypoxic cycling exercise. Exercise fatigue was evaluated by ratings of perceived exertion (RPE), arm maximal voluntary force (MVC), and voluntary activation of elbow flexor muscles assessed with transcranial magnetic stimulation. Low intensity exercise did not produce any indication of central fatigue or marked cerebral metabolic deviations. Exercise in hypoxia (0.10) reduced cerebral oxygen delivery 25% and decreased 11+/-4 mmHg (P<0.001) together with OCI (6.2+/-0.7 to 4.8+/-0.5, P<0.001). RPE increased while MVC and voluntary activation were reduced (P<0.05). During maximal exercise declined 8+/-4 mmHg (P<0.05) and OCI to 3.8+/-0.5 (P<0.001). RPE was 18.5, and MVC and voluntary activation were reduced (P<0.05). We observed no signs of muscular fatigue in the elbow flexors and all control MVCs were similar to resting values. Exhaustive exercise provoked cerebral deoxygenation, metabolic changes and indices of fatigue similar to those observed during exercise in hypoxia indicating that reduced cerebral oxygenation may play a role in the development of central fatigue and may be an exercise capacity limiting factor.
authors.affiliation: Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, AN2041, Blegdamsvej 9, DK2100 Copenhagen, Denmark. peter@prec.dk
authors.forename: P
authors.initials: P
authors.lastname: Rasmussen
authors.forename: J
authors.initials: J
authors.lastname: Nielsen
authors.forename: M
authors.initials: M
authors.lastname: Overgaard
authors.forename: R
authors.initials: R
authors.lastname: Krogh-Madsen
authors.forename: A
authors.initials: A
authors.lastname: Gjedde
authors.forename: N H
authors.initials: NH
authors.lastname: Secher
authors.forename: N C
authors.initials: NC
authors.lastname: Petersen
mesh_terms: D000328:Adult; D000465:Algorithms; D001786:Blood Glucose / Q000378:metabolism; D001923:Brain Chemistry / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D004550:Elbow / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D002534:Hypoxia, Brain / Q000503:physiopathology; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D006454:Hemoglobins; D002245:Carbon Dioxide; D019344:Lactic Acid; D010100:Oxygen
references.citation: J Cereb Blood Flow Metab. 2007 May;27(5):1082-93
references.pmid: 17077816
references.citation: Neurosurgery. 1993 May;32(5):737-41; discussion 741-2
references.pmid: 8492848
references.citation: J Appl Physiol (1985). 1994 Feb;76(2):634-40
references.pmid: 8175572
references.citation: Am J Physiol Heart Circ Physiol. 2008 Jan;294(1):H164-71
references.pmid: 18032522
references.citation: J Cereb Blood Flow Metab. 2009 Jun;29(6):1121-9
references.pmid: 19337275
references.citation: Neuroradiology. 1976;10(5):257-62
references.pmid: 945488
references.citation: J Appl Physiol (1985). 2009 Apr;106(4):1153-8
references.pmid: 19150853
references.citation: J Physiol. 1995 Oct 1;488 ( Pt 1):219-29
references.pmid: 8568658
references.citation: J Physiol. 2008 Jun 1;586(11):2807-15
references.pmid: 18403423
references.citation: J Physiol. 2003 Sep 1;551(Pt 2):661-71
references.pmid: 12909682
references.citation: Am J Physiol Regul Integr Comp Physiol. 2004 Sep;287(3):R534-40
references.pmid: 15155282
references.citation: J Clin Invest. 1948 Jul;27(4):484-92
references.pmid: 16695569
references.citation: Prog Neurobiol. 2004 Mar;72(4):223-61
references.pmid: 15142684
references.citation: J Appl Physiol (1985). 2002 Jul;93(1):58-64
references.pmid: 12070186
references.citation: J Appl Physiol (1985). 1992 Aug;73(2):420-6
references.pmid: 1399960
references.citation: Neuroimage. 2002 Jan;15(1):74-82
references.pmid: 11771975
references.citation: Fed Proc. 1957 Sep;16(3):666-71
references.pmid: 13480339
references.citation: J Appl Physiol (1985). 1992 Nov;73(5):1825-30
references.pmid: 1474058
references.citation: J Cereb Blood Flow Metab. 2006 Jun;26(6):731-50
references.pmid: 16395281
references.citation: J Physiol. 2008 Jan 1;586(1):161-73
references.pmid: 17962334
references.citation: J Appl Physiol (1985). 2002 Apr;92(4):1487-93
references.pmid: 11896014
references.citation: J Cereb Blood Flow Metab. 1993 Jul;13(4):646-55
references.pmid: 8314918
references.citation: Stroke. 2000 Jul;31(7):1672-8
references.pmid: 10884472
references.citation: J Appl Physiol (1985). 1999 Nov;87(5):1604-8
references.pmid: 10562597
references.citation: J Physiol. 2002 Apr 15;540(Pt 2):681-9
references.pmid: 11956354
references.citation: J Physiol. 1954 Mar 29;123(3):553-64
references.pmid: 13152698
references.citation: J Cereb Blood Flow Metab. 2000 Apr;20(4):747-54
references.pmid: 10779019
references.citation: Acta Physiol Scand. 1996 Jun;157(2):187-90
references.pmid: 8800358
references.citation: Acta Physiol Scand Suppl. 1995;625:1-44
references.pmid: 7484167
references.citation: J Cereb Blood Flow Metab. 2005 Sep;25(9):1183-96
references.pmid: 15815583
references.citation: Proc Natl Acad Sci U S A. 1986 Feb;83(4):1140-4
references.pmid: 3485282
references.citation: J Physiol. 2009 Jan 15;587(1):285-93
references.pmid: 19015195
references.citation: Science. 1988 Jul 22;241(4864):462-4
references.pmid: 3260686
references.citation: J Physiol. 2004 Jan 15;554(Pt 2):571-8
references.pmid: 14608005
references.citation: J Appl Physiol (1985). 1996 Jul;81(1):413-8
references.pmid: 8828693
references.citation: J Appl Physiol (1985). 1999 Dec;87(6):1997-2006
references.pmid: 10601141
references.citation: Am J Physiol. 1999 Sep;277(3):H1045-52
references.pmid: 10484427
references.citation: Proc Natl Acad Sci U S A. 1994 Oct 25;91(22):10625-9
references.pmid: 7938003
references.citation: J Appl Physiol (1985). 2002 Feb;92(2):486-92
references.pmid: 11796655
references.citation: J Physiol. 1996 Jan 15;490 ( Pt 2):529-36
references.pmid: 8821149
references.citation: Exp Physiol. 2007 Mar;92(2):417-26
references.pmid: 17099060
references.citation: J Cereb Blood Flow Metab. 1999 Apr;19(4):393-400
references.pmid: 10197509
references.citation: J Cereb Blood Flow Metab. 2010 Jun;30(6):1240-6
references.pmid: 20179724
references.citation: Physiol Rev. 2001 Oct;81(4):1725-89
references.pmid: 11581501
references.citation: Eur J Appl Physiol. 2006 Feb;96(3):299-304
references.pmid: 16284788
references.citation: Exerc Sport Sci Rev. 2007 Jul;35(3):110-8
references.pmid: 17620929