The phase 1, or cardiodynamic phase (Whipp et al. 1982), is followed by a primary and rapid exponential process (phase 2), with the third phase characterised by a delayed rise in _ VO2 (slow component) which causes _ VO2 to increase toward an elevated steady state, or else it is truncated by the achievement of peak _ VO2 (Gaesser and Poole 1996).