Overshoot in VO₂ following the onset of moderate-intensity cycle exercise in trained cyclists

Authors: Koppo, K.¹; Whipp, B.²; Jones, A.³; Aeyels, D.⁴; Bouckaert, J.⁵

Source: European Journal of Applied Physiology, Volume 93, Number 3, December 2004 , pp. 366-373(8)

Publisher: Springer

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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 VO₂responses 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 VO_2peak, seven trained cyclists [mean (SD); VO_2peak 66.6 (2.5) ml·kg⁻¹·min⁻¹] and eight sedentary subjects [VO_2peak 42.9 (5.1) ml·kg⁻¹·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 VO_2peak (50%Δ). 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 ~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 ~55 and 140 s]. None of the cyclists showed an overshoot at 50%Δ. 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.

Keywords: Cycling exercise; Efficiency; Modelling; VO2 kinetics

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s00421-004-1229-8

Affiliations: 1: Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000 , Ghent, Belgium, Email: katrien.koppo@UGent.be 2: Division of Respiratory and Critical Care Physiology and Medicine, Harbor-UCLA Medical Center, Torrance, CA 90509, USA, 3: Department of Exercise and Sport Science, Manchester Metropolitan University, Alsager , ST7 2HL, UK, 4: Department of Electrical Energy, Systems and Automation, Ghent University, 9000 , Ghent, Belgium, 5: Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000 , Ghent, Belgium,

Publication date: 2004-12-01