Identifying bottlenecks in endurance performance: the conductance theorem

The various transport processes that contribute to human endurance performance, such as oxygen intake, elimination of carbon dioxide, lactate and heat, and the delivery of metabolic fuels, can all be represented by conductance analogues. The use of such models is helpful in identifying bottlenecks within each of these systems, and in comparing parallel systems such as the intake of oxygen and the elimination of carbon dioxide. However, in order to make the models manageable, many simplifications are necessary, and corresponding caution is needed in drawing inferences from conductance analogues.