Model simulation of blood flow and oxygen uptake during exercise.

We developed a dynamic model to account for blood flow in the working muscle during step changes in work rate. The model contains a proportional controller based on oxygen tension in the muscle and a description of the various oxygen-equivalent energy stores. Because of nonlinearities only particular solutions can be obtained. Such solutions were obtained via the finite difference method for various work levels and regimens. Model predictions are presented in comparisons with new experimental data, and with data reported in the literature. The changes in oxygen-equivalent energy stores and in muscle blood flow occur very rapidly after onset of exercise, with at least 90% of the steady-state response being reached within 90 sec.