title: The relationship between critical speed and the respiratory compensation point: Coincidence or equivalence.
abstract: It has previously been suggested that the respiratory compensation point (RCP) and critical speed (CS) parameters are equivalent and, therefore, like CS, RCP demarcates the boundary between the heavy- and severe-intensity domains. However, these findings are equivocal and therefore must be interpreted cautiously. Thus, we examined the relationship between CS and RCP across a wide range of subject fitness levels, in an attempt to determine if CS and RCP are equivalent. Forty men and 30 women (age: 23.2 ± 2.5 year, height: 174 ± 10 cm, body mass: 74.1 ± 15.7 kg) completed an incremental and four constant-speed protocols on a treadmill. RCP was determined as the point at which the minute ventilation increased disproportionately to CO2 production and the end-tidal CO2 partial pressure began to decrease. CS was determined from the constant-speed protocols using the linearized 1·time(-1) model. CS and RCP, expressed as speed or metabolic rate, were not significantly different (11.7 ± 2.3 km·h(-1) vs. 11.5 ± 2.3 km·h(-1), p = 0.208; 2.88 ± 0.80 l·min(-1) vs. 2.83 ± 0.72 l·min(-1), p = 0.293) and were significantly correlated (r(2) = 0.52, p < 0.0001; r(2) = 0.74, p < 0.0001, respectively). However, there was a high degree of variability between the parameters. The findings of the current study indicate that, while on average CS and RCP were not different, the high degree of variability between these parameters does not permit accurate estimation of one from the other variable and suggests that these parameters may not be physiologically equivalent.
authors.affiliation: a Department of Anatomy and Physiology , Kansas State University , Manhattan , KS , USA.|b Department of Kinesiology , Kansas State University , Manhattan , KS , USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Broxterman
authors.affiliation: c Department of Health and Exercise Science , University of Oklahoma , Norman , OK , USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Ade
authors.affiliation: b Department of Kinesiology , Kansas State University , Manhattan , KS , USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Craig
authors.affiliation: b Department of Kinesiology , Kansas State University , Manhattan , KS , USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Wilcox
authors.affiliation: b Department of Kinesiology , Kansas State University , Manhattan , KS , USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Schlup
authors.affiliation: b Department of Kinesiology , Kansas State University , Manhattan , KS , USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Barstow
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000378:metabolism*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012044:Regression Analysis; D012119:Respiration; D012420:Running / Q000502:physiology*; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: Critical speed; exercise intensity domains; respiratory compensation point