title: Modeling Intermittent Cycling Performance in Hypoxia Using the Critical Power Concept.
abstract: OBJECTIVE
  This study investigated the efficacy of an intermittent critical power (CP) model, termed the "work-balance" (W'BAL) model, during high-intensity exercise in hypoxia (HYPO).
  
  
  METHODS
  Eleven trained male cyclists (mean ± SD age, 27 ± 6.6 yr; V˙O2peak, 4.79 ± 0.56 L·min(-1)) completed a maximal ramp test and a 3-min "all-out" test to determine CP and work performed above CP (W'). On another day, an intermittent exercise test to task failure was performed. All procedures were performed in normoxia (NORM) and HYPO (FiO2 ≈ 0.155) in a single-blind, randomized, and counter-balanced experimental design. The W'BAL model was used to calculate the minimum W' (W'BALmin) achieved during the intermittent test. The W'BALmin in HYPO was also calculated using CP + W' derived in NORM (N + H).
  
  
  RESULTS
  In HYPO, there was an 18% decrease in V˙O2peak (4.79 ± 0.56 vs 3.93 ± 0.47 L·min(-1); P < 0.001) and a 9% decrease in CP (347 ± 45 vs 316 ± 46 W; P < 0.001). No significant change for W' occurred (13.4 ± 3.9 vs 13.7 ± 4.9 kJ; P = 0.69; NORM vs HYPO). The change in V˙O2peak was significantly correlated with the change in CP (r = 0.72; P = 0.01). There was no difference between NORM and HYPO for W'BALmin (1.1 ± 0.9 kJ vs 1.2 ± 0.6 kJ). The N + H analysis grossly overestimated W'BALmin (7.8 ± 3.4 kJ) compared with HYPO (P < 0.001).
  
  
  CONCLUSIONS
  The W'BAL model produced similar results in HYPO and NORM, but only when model parameters were determined under the same environmental conditions as the performance task. Application of the W'BAL model at altitude requires a modification of the model or that CP and W' are measured at altitude.
authors.affiliation: 1Centre for Exercise & Sport Science, Deakin University, Geelong, AUSTRALIA; 2Department of Sports Medicine, Advocate Lutheran General Hospital, Park Ridge, IL; and 3Athlete Health and Performance Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, QATAR.
authors.forename: Samantha
authors.initials: S
authors.lastname: Shearman
authors.forename: Dan
authors.initials: D
authors.lastname: Dwyer
authors.forename: Philip
authors.initials: P
authors.lastname: Skiba
authors.forename: Nathan
authors.initials: N
authors.lastname: Townsend
mesh_terms: D000328:Adult; D000531:Altitude; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D005080:Exercise Test; D005221:Fatigue; D006801:Humans; D000860:Hypoxia; D008297:Male; D008962:Models, Theoretical; D010101:Oxygen Consumption; D016037:Single-Blind Method; D055815:Young Adult