title: Neuromuscular adjustments of the quadriceps muscle after repeated cycling sprints.
abstract: OBJECTIVE
  This study investigated the supraspinal processes of fatigue of the quadriceps muscle in response to repeated cycling sprints.
  
  
  METHODS
  Twelve active individuals performed 10 × 6-s "all-out" sprints on a cycle ergometer (recovery = 30 s), followed 6 min later by 5 × 6-s sprints (recovery = 30 s). Transcranial magnetic and electrical femoral nerve stimulations during brief (5-s) and sustained (30-s) isometric contractions of the knee extensors were performed before and 3 min post-exercise.
  
  
  RESULTS
  Maximal strength of the knee extensors decreased during brief and sustained contractions (~11% and 9%, respectively; P<0.001). Peripheral and cortical voluntary activation, motor evoked potential amplitude and silent period duration responses measured during briefs contractions were unaltered (P>0.05). While cortical voluntary activation declined (P<0.01) during the sustained maximal contraction in both test sessions, larger reductions occurred (P<0.05) after exercise. Lastly, resting twitch amplitude in response to both femoral nerve and cortical stimulations was largely (> 40%) reduced (P<0.001) following exercise.
  
  
  CONCLUSIONS
  The capacity of the motor cortex to optimally drive the knee extensors following a repeated-sprint test was shown in sustained, but not brief, maximal isometric contractions. Additionally, peripheral factors were largely involved in the exercise-induced impairment in neuromuscular function, while corticospinal excitability was well-preserved.
authors: Aspetar, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. oliv.girard@gmail.com
authors: Olivier
authors: O
authors: Girard
authors: David J
authors: DJ
authors: Bishop
authors: Sébastien
authors: S
authors: Racinais
mesh_terms: D000328:Adult; D001642:Bicycling; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018763:Muscle Fatigue; D009469:Neuromuscular Junction / Q000502:physiology; D005082:Physical Exertion; D052097:Quadriceps Muscle / Q000294:innervation* / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation
references: Med Sci Sports Exerc. 2004 May;36(5):807-13
references: 15126714
references: Muscle Nerve. 2009 Feb;39(2):186-96
references: 19034956
references: J Physiol. 2012 Jun 1;590(11):2767-82
references: 22473785
references: J Appl Physiol (1985). 2008 Feb;104(2):542-50
references: 18032577
references: Eur J Appl Physiol. 2010 Sep;110(1):1-15
references: 20419312
references: Eur J Appl Physiol. 2008 Jul;103(4):411-9
references: 18368419
references: Physiol Rev. 2008 Jan;88(1):287-332
references: 18195089
references: Med Sci Sports Exerc. 2007 Dec;39(12):2219-25
references: 18046194
references: Exp Brain Res. 1993;93(1):181-4
references: 8467889
references: J Appl Physiol (1985). 2009 Feb;106(2):556-65
references: 19056999
references: J Appl Physiol (1985). 2009 Jul;107(1):354-5
references: 18801954
references: Int J Sports Med. 2005 May;26(4):245-52
references: 15795808
references: Exp Physiol. 2009 Sep;94(9):995-1004
references: 19561142
references: J Neurophysiol. 1999 Nov;82(5):2271-83
references: 10561405
references: J Appl Physiol (1985). 1993 Aug;75(2):712-9
references: 8226473
references: Sports Med. 2011 Aug 1;41(8):673-94
references: 21780851
references: J Physiol. 2008 Jun 1;586(11):2799-805
references: 18403421
references: J Appl Physiol (1985). 2000 Jul;89(1):305-13
references: 10904066
references: Eur J Appl Physiol. 2010 Aug;109(6):1027-36
references: 20358218
references: J Appl Physiol (1985). 2012 Mar;112(5):849-58
references: 22174405
references: Scand J Med Sci Sports. 2013 Feb;23(1):57-65
references: 21812824
references: Muscle Nerve. 1998 Mar;21(3):318-28
references: 9486860
references: J Physiol. 1993 Jul;466:521-34
references: 8410704
references: J Appl Physiol (1985). 2010 Dec;109(6):1842-51
references: 20813979
references: J Appl Physiol (1985). 2006 Jun;100(6):1757-64
references: 16424071
references: Med Sci Sports Exerc. 2007 Feb;39(2):268-74
references: 17277590
references: J Physiol. 2003 Sep 1;551(Pt 2):661-71
references: 12909682
references: J Appl Physiol (1985). 2009 Jul;107(1):355-7; discussion 357-8
references: 19567806
references: Muscle Nerve. 2007 Apr;35(4):486-95
references: 17221875
references: J Physiol. 1996 Jan 15;490 ( Pt 2):519-28
references: 8821148
references: Psychophysiology. 2012 Jun;49(6):853-65
references: 22416901
references: J Appl Physiol (1985). 2007 May;102(5):1756-66
references: 17218428
references: J Appl Physiol (1985). 2004 Jul;97(1):236-42
references: 15033969
references: J Neurosci Methods. 1997 Jun 27;74(2):113-22
references: 9219881