Systolic and Diastolic LV Mechanics during and following Resistance Exercise.

PURPOSE: To improve the current understanding of the impact of resistance exercise on the heart, by examining the acute responses of left ventricular (LV) strain, twist and untwisting rate ('LV mechanics').

METHODS: LV echocardiographic images were recorded in systole and diastole before, during and immediately after (7-12 s) double leg press exercise at two intensities (30% and 60% of maximum strength, 1-repetition-maximum, 1RM). Speckle tracking analysis generated LV strain, twist and untwisting rate data. Additionally, beat-by-beat blood pressure was recorded and systemic vascular resistance (SVR) and LV wall stress were calculated.

RESULTS: Responses in both exercise trials were statistically similar (P > 0.05). During effort, stroke volume decreased while SVR and LV wall stress increased (P < 0.05). Immediately following effort, stroke volume returned to baseline while SVR and wall stress decreased (P < 0.05). Similarly, acute exercise was accompanied by a significant decrease in systolic parameters of LV muscle mechanics (P < 0.05). However, diastolic parameters, including LV untwisting rate, were statistically unaltered (P > 0.05). Immediately following exercise, systolic LV mechanics returned to baseline levels (P < 0.05) but LV untwisting rate increased significantly (P < 0.05).

CONCLUSIONS: A single, acute bout of double leg-press resistance exercise transiently reduces systolic LV mechanics, but increases diastolic mechanics following exercise, suggesting that resistance exercise has a differential impact on systolic and diastolic heart muscle function. The findings may explain why acute resistance exercise has been associated with reduced stroke volume but chronic exercise training may result in increased LV volumes.