title: The relationship between oxygen uptake kinetics and neuromuscular fatigue in high-intensity cycling exercise.
abstract: OBJECTIVE
  In theory, a slow oxygen uptake ([Formula: see text]) kinetics leads to a greater accumulation of anaerobic by-products, which can, in turn, induce more neuromuscular fatigue. However, the existence of this relationship has never been tested.
  
  
  METHODS
  After two sessions to measure peak [Formula: see text], peak power output (POpeak), and [Formula: see text] kinetics responses in the unfatigued state (τ [Formula: see text] MOD), 10 healthy young adults performed a 6-min cycling bout at 80% POpeak(INT6-min). [Formula: see text] kinetics responses were also measured during INT6-min. Neuromuscular fatigue was measured isometrically pre- and post-INT6-min(immediately post- and 15-s post-INT6-min) with an innovative cycle ergometer.
  
  
  RESULTS
  Maximal voluntary contraction (MVC) force, high-frequency doublet amplitude, and the ratio of low- to high-frequency doublet amplitudes decreased by 34 ± 7, 43 ± 11, and 31 ± 13%, respectively (all P < 0.01). A significant Spearman's rank correlation was observed between the change in low-frequency doublet force (ΔDb10) immediately after INT6-minand both τ [Formula: see text] MOD and τ [Formula: see text] INT6-min(ρ = -0.68 and ρ = -0.67, both P < 0.05). When considering the largest responses from the two neuromuscular evaluations post-INT6-min, significant correlations were also found between τ [Formula: see text] MOD and ΔDb10 (ρ = -0.74; P < 0.05) and between τ[Formula: see text] INT6-minand both ΔDb10 and low-frequency fatigue (ρ = -0.70 and ρ = -0.66; both P < 0.05).
  
  
  CONCLUSIONS
  The present results suggest that subjects with slow [Formula: see text] kinetics experience more peripheral fatigue, in particular more excitation-contraction coupling failure, likely due to a greater accumulation of protons and/or inorganic phosphates.
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Temesi
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Felipe
authors.initials: F
authors.lastname: Mattioni Maturana
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Arthur
authors.initials: A
authors.lastname: Peyrard
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Tatiane
authors.initials: T
authors.lastname: Piucco
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Murias
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada. gmillet@ucalgary.ca.
authors.forename: Guillaume Y
authors.identifier: http://orcid.org/0000-0002-6395-0762
authors.initials: GY
authors.lastname: Millet
mesh_terms: D000328:Adult; D056966:Excitation Contraction Coupling; D005260:Female; D000072696:High-Intensity Interval Training; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D010101:Oxygen Consumption
keywords: Excitation–contraction coupling failure; Intense cycling exercise; Muscle fatigue; Oxygen uptake kinetics