Recent studies have reported evidence of both a short-term and a more sustained reduction in left ventricular diastolic function after prolonged strenuous exercise. Interpretation of this data is confounded by alterations in heart rate (HR) post-exercise. The purpose of this study was to investigate the association between HR and diastolic function during recovery from supine exercise, and to reassess the impact of increasing HR on early diastolic flow and tissue velocities during supine exercise. Repeat echocardiograms in 16 young, trained, volunteers were obtained at rest (50 +/- 6 beats.min-1), during steady-state supine cycling at HR of 60, 80, and 100 beats.min-1, and then during supine recovery at HR of 80 and 60 beats.min-1. Doppler flow velocities and tissue Doppler myocardial annular velocities were recorded in early (E and E', respectively) and late diastole (A and A', respectively). The ratios E/A, E'/A', and E/E' were calculated. Data were compared via analyses of variance (ANOVA; exercise) and t tests (recovery). Peak E, A, E', and A' all increased in line with HR during exercise (p < 0.05) although relatively greater changes in A and A' resulted in a significant decline in E/A and E'/A' with increasing HR (p < 0.05). During recovery E, A, E', and A' all declined from peak values during exercise (p < 0.05). At 80 beats.min-1, flow and tissue Doppler data were still elevated above resting values and only A was significantly reduced compared with assessments made at the same HR during exercise. Diastolic flow and tissue velocities tended to increase (during supine exercise) and return to baseline (during recovery from exercise) in line with changes in HR. The interpretation of diastolic functional indices measured after physical exertion should be made in light of the present data.