This a model for teaching the effect of certain variables have on such things as a

This a model that helps clarify the effect of change in individual parameters
and how they can materially affect the overall haemodynamic picture. It is designed for elderly patients - not athletes. (E&OE)

Mixed venous
gases at the
AT

pH = 7.29
pO2 = 28
pCO2 = 55

These are figures are approximated from:
J Appl Physiol
1997;82:908-912

Set the mixed venous gases to the likely values at the anaerobic threshold (AT). They are displayed on the left of the model. This will change the C(a-v)O2. This divided into the oxygen uptake at that time i.e. at the AT, will give you the cardiac output at that time. Change the Hb or any other parameter and you will see the extent of changes induced. Obviously these are approximations and do not take into account such issues as haemoconcentration during exercise or methaemoglobin etc.