title: (.)VO(2) and EMG activity kinetics during moderate and severe constant work rate exercise in trained cyclists.
abstract: The purpose of this study was to compare O(2) uptake ((.)VO(2)) and muscle electromyography activity kinetics during moderate and severe exercise to test the hypothesis of progressive recruitment of fast-twitch fibers in the explanation of the VO(2) slow component. After an incremental test to exhaustion, 7 trained cyclists (mean +/- SD, 61.4 +/- 4.2 ml x min(-1) x kg(- 1)) performed several square-wave transitions for 6 min at moderate and severe intensities on a bicycle ergometer. The (.)VO(2) response and the electrical activity (i.e., median power frequency, MDF) of the quadriceps vastus lateralis and vastus medialis of both lower limbs were measured continuously during exercise. After 2 to 3 min of exercise onset, MDF values increased similarly during moderate and severe exercise for almost all muscles whereas a (.)VO(2) slow component occurred during severe exercise. There was no relationship between the increase of MDF values and the magnitude of the (.)VO(2) slow component during the severe exercise. These results suggest that the origin of the slow component may not be due to the progressive recruitment of fast-twitch fibers.
authors.affiliation: Lab. De Physiologie de l Exercice Musculaire, Univ. d Orleans, 45100 Orleans la Source, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Cleuziou
authors.forename: Stephane
authors.initials: S
authors.lastname: Perrey
authors.forename: Fabio
authors.initials: F
authors.lastname: Borrani
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Lecoq
authors.forename: Daniel
authors.initials: D
authors.lastname: Courteix
authors.forename: Philippe
authors.initials: P
authors.lastname: Germain
authors.forename: Philippe
authors.initials: P
authors.lastname: Obert
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology; D013647:Task Performance and Analysis; D013997:Time Factors