Abstract

Traditionally, it has been accepted that, during incremental exercise, stroke volume plateaus at 40% of Vo₂max. However, recent research has documented that stroke volume progressively increases to Vo₂max in both trained and untrained subjects. The stroke volume response to incremental exercise to Vo₂max may be influenced by training status, age, and sex. For endurance trained subjects, the proposed mechanisms for the progressive increase in stroke volume to Vo₂max are enhanced diastolic filling, enhanced contractility, larger blood volume, and decreased cardiac afterload. For untrained subjects, it has been proposed that continued increases in stroke volume may result from a naturally occurring high blood volume. However, additional research is needed to evaluate the importance of blood volume, or other mechanisms, that influence the stroke volume response to exercise in untrained subjects.