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A Comparison of Modelling Techniques used to Characterise Oxygen Uptake Kinetics During the on‐Transient of Exercise
Author(s) -
Bell Christopher,
Paterson Donald H.,
Kowalchuk John M.,
Padilla Javier,
Cunningham David A.
Publication year - 2001
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/eph8602150
Subject(s) - intensity (physics) , exponential function , component (thermodynamics) , phase (matter) , steady state (chemistry) , time constant , amplitude , mathematics , vo2 max , constant (computer programming) , chemistry , physics , medicine , thermodynamics , mathematical analysis , heart rate , computer science , organic chemistry , quantum mechanics , electrical engineering , engineering , blood pressure , programming language
We compared estimates for the phase 2 time constant (τ) of oxygen uptake (V̇ O2 ) during moderate‐ and heavy‐intensity exercise, and the slow component of V̇ O2 during heavy‐intensity exercise using previously published exponential models. Estimates for τ and the slow component were different (P < 0.05) among models. For moderate‐intensity exercise, a two‐component exponential model, or a mono‐exponential model fitted from 20 s to 3 min were best. For heavy‐intensity exercise, a three‐component model fitted throughout the entire 6 min bout of exercise, or a two‐component model fitted from 20 s were best. When the time delays for the two‐ and three‐component models were equal the best statistical fit was obtained; however, this model produced an inappropriately low ΔV̇ O2 /ΔWR (WR, work rate) for the projected phase 2 steady state, and the estimate of phase 2 τ was shortened compared with other models. The slow component was quantified as the difference between V̇ O2 at end‐exercise (6 min) and at 3 min (ΔV̇ O2 (6‐3 min) ; 259 ml min −1 ), and also using the phase 3 amplitude terms (truncated to end‐exercise) from exponential fits (409‐833 ml min −1 ). Onset of the slow component was identified by the phase 3 time delay parameter as being of delayed onset ∼2 min (vs. arbitrary 3 min). Using this delay ΔV̇ O2 (6‐2 min) was ∼400 ml min −1 . Use of valid consistent methods to estimate τ and the slow component in exercise are needed to advance physiological understanding.