title: Overshoot in VO2 following the onset of moderate-intensity cycle exercise in trained cyclists.
abstract: We have previously observed that following the onset of moderate intensity cycle ergometry, the pulmonary O2 uptake (VO2) in trained cyclists often does not increase towards its steady-state value with the typical mono-exponential characteristics; rather, there is a transient "overshoot". The purpose of this study was to systematically examine this phenomenon by comparing the VO2 responses to two moderate-intensity work rates and one high-intensity work rate in trained and untrained subjects. Following a ramp exercise test to the limit of tolerance for the determination of the gas exchange threshold (GET) and VO2(peak), seven trained cyclists [mean (SD); VO2(peak) 66.6 (2.5) ml x kg(-1) x min(-1)] and eight sedentary subjects [VO2(peak) 42.9 (5.1) ml x kg(-1) x min(-1)] completed six step transitions from baseline cycling to work rates requiring 60% and 80% GET and three step transitions from baseline cycling to a work rate requiring 50% of the difference between GET and VO2(peak) (50%delta). VO2 was measured breath-by-breath and modelled using standard techniques. The sedentary subjects did not overshoot the steady-state VO2 at any intensity. At 60% GET, six of the seven cyclists overshot the steady-state VO2 [by an integral volume of 164 (44) ml between approximately 45 and 125 s]. At 80% GET, four of the seven cyclists overshot the steady-state VO2 [by an integral volume of 185 (92) ml between approximately 55 and 140 s]. None of the cyclists showed an overshoot at 50%delta. These results indicate that trained cyclists evidence an overshoot in VO2 before steady-state is reached in the transition to moderate-intensity exercise. The mechanism(s) responsible for this effect remains to be elucidated, as does whether the overshoot confers any functional or performance benefit to the trained cyclist.
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000 Ghent, Belgium. katrien.koppo@UGent.be
authors.forename: K
authors.initials: K
authors.lastname: Koppo
authors.forename: B J
authors.initials: BJ
authors.lastname: Whipp
authors.forename: A M
authors.initials: AM
authors.lastname: Jones
authors.forename: D
authors.initials: D
authors.lastname: Aeyels
authors.forename: J
authors.initials: J
authors.lastname: Bouckaert
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*
chemical_list: D010100:Oxygen