Effect of Aquatic Exercise Training on Left Ventricular Afterload in in Middle‐aged and Older Normotensives: Evaluation by Polar coordinate description

Abstract

Regular aerobic physical activity has been recommended to prevent the age‐related increase in cardiovascular disease risks. However, the effect of in‐water aerobic exercise training (e.g., swimming, head‐out aquatic exercise) on the aortic augmentation index (AIx), an index of left ventricular afterload, is inconsistent. Recently, there has been a gaining recognition about the limitations of dimensionless ratio‐based metrics, including AIx (=augmentation pressure [AP]/pulse pressure [PP]). The single‐use of ratio would provide incomplete information relative to the “content” of the two components: since AP is a component of PP, the training‐induced change in AP might be masked by the corresponding change in PP. Accordingly, using the newly proposed companion metrics of AIx by polar coordinate description, we determined the effect of head‐out aquatic exercise training on left ventricular afterload in middle‐aged and older adults. We evaluated aortic hemodynamics in 15 normotensives (62±10 y.o., four men) before and after a 15‐week aquatic exercise course. Aortic hemodynamics were estimated from brachial arterial pressure waveforms via the general transfer function method. Companion metrics of AIx (AIxC=√{AP2+PP2}) were calculated as measures of arterial load. The participation rate in the training course was 86 %. Aortic systolic blood pressure (SBP) decreased after the training course (from 112±8 to 108±11 mmHg, P=0.02). AIxC also decreased (from 45±7 to 42±7 mmHg2, P=0.01). In contrast, AIx remained unchanged (from 47±10 to 45±11 %, P=0.148) presumably due to parallel changes in AP (from 19±5 to 17±5 mmHg, P=0.002) and PP (from 41±6 to 39±6 mmHg, P=0.01). These findings suggest that head‐out aquatic exercise training might lower the left ventricular afterload in middle‐aged and older normotensives. The newly introduced companion metric may provide better insight into underlying physiology.