title: Evidence of neuromuscular fatigue after prolonged cycling exercise.
abstract: OBJECTIVE
  The purpose of this study was to analyze the effects of prolonged cycling exercise on metabolic, neuromuscular, and biomechanical parameters.
  
  
  METHODS
  Eight well-trained male cyclists or triathletes performed a 2-h cycling exercise at a power output corresponding to 65% of their maximal aerobic power. Maximal concentric (CON; 60, 120, 240 degrees x s(-1)), isometric (ISO; 0 degrees s(-1)), and eccentric (ECC; -120, -60 degrees x s(-1)) contractions, electromyographic (EMG) activity of vastus lateralis (VL) and vastus medialis (VM) muscles were recorded before and after the exercise. Neural (M-wave) and contractile (isometric muscular twitch) parameters of quadriceps muscle were also analyzed using electrical stimulation techniques.
  
  
  RESULTS
  Oxygen uptake (VO2), minute ventilation (VE), and heart rate (HR) significantly increased (P < 0.01) during the 2-h by, respectively, 9.6%, 17.7%, and 12.7%, whereas pedaling rate significantly decreased (P < 0.01) by 21% (from 87 to 69 rpm). Reductions in muscular peak torque were quite similar during CON, ISO, and ECC contractions, ranging from 11 to 15%. M-wave duration significantly increased (P < 0.05) postexercise in both VL and VM, whereas maximal amplitude and total area decreased (VM: P < 0.05, VL: NS). Significant decreases in maximal twitch tension (P < 0.01), total area of mechanical response (P < 0.01), and maximal rate of twitch tension development (P < 0.05) were found postexercise.
  
  
  CONCLUSIONS
  A reduction in leg muscular capacity after prolonged cycling exercise resulted from both reduced neural input to the muscles and a failure of peripheral contractile mechanisms. Several hypothesis are proposed to explain a decrease in pedaling rate during the 2-h cycling with a constancy of power output and an increase in energy cost.
authors.affiliation: Groupe Analyse du Mouvement, UFR STAPS, Université de Bourgogne, Dijon, France. romuald.lepers@u-bourgogne.fr
authors.forename: R
authors.initials: R
authors.lastname: Lepers
authors.forename: C
authors.initials: C
authors.lastname: Hausswirth
authors.forename: N
authors.initials: N
authors.lastname: Maffiuletti
authors.forename: J
authors.initials: J
authors.lastname: Brisswalter
authors.forename: J
authors.initials: J
authors.lastname: van Hoecke
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001696:Biomechanical Phenomena; D004562:Electrocardiography; D004576:Electromyography; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D012143:Respiratory Physiological Phenomena; D013997:Time Factors