Introduction
The relationship between resting echocardiographic measures of cardiac function and exercise capacity is weak 1–4. At peak exercise, left ventricular (LV) function, especially longitudinal motion, is better correlated with maximum exercise capacity5. The shape of the relationship, as well as the relative contribution of various measurable facets of heart function is not known. Amongst athletes with phenotypically abnormal hearts, augmentation of left ventricular ejection fraction (LVEF) by more than 10% differentiates those with adaptive rather than cardiomyopathic hearts 6,7. Understanding the shape to the relationship between contractile reserve and exercise attainment is vital to understand the physiology, and to establish target parameters that might be useful when investigating disease states. We therefore hypothesized that detailed measures of exercise myocardial recruitment would explain individual exercise performance, and that longitudinal function would be the primary adaptive strategy. This was achieved by recording oxygen uptake (VO2) and echocardiography simultaneously across an incremental exercise protocol in a cohort of healthy volunteers.