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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 …