Exercise in Water Provides Better Cardiac Energy Efficiency Than on Land

Figures

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  Figure 1. Schema of aortic pulse wave analysis. Augmentation pressure (AP) is the difference between the first systolic peak (or shoulder) and the second systolic peak pressure. Augmentation index (AIx) is defined as the AP as a percentage of pulse pressure. The dicrotic notch (DN) represents the closure of the aortic valve and is used to calculate ejection duration. Aortic tension-time index (TTI) and diastolic pressure-time index (DTI) are areas under the aortic systolic and diastolic pressure-time curve (both measured from 0 mmHg) and reflect the myocardial oxygen demand and the blood supply to the heart, respectively. The subendocardial viability ratio (SEVR) is the ratio of DTI to TTI.

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  Figure 2. Stroke volume (SV) response at rest and during exercise. Symbols and error bars are mean and SD. The circle and square indicate water-based and land-based exercise, respectively. The P-values for the two-way repeated ANOVA data are presented (environment, intensity, and interaction). a,b,cshow significant differences from rest, stage 1, and stage 2 of the same environment, respectively. *indicates a significant difference from land at the same stage.

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  Figure 3. Myocardial oxygen supply-to-demand balance indicators at rest and during exercise. Symbols and error bars are mean and SD. The circle and square indicate water-based and land-based exercise, respectively. The P-values for the two-way repeated ANOVA data are presented (intensity, environment, and interaction).

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  Figure 4. The maximum rate of aortic pressure rise (dP/dTmax) response at rest and during exercise and scatter plot of change in SV in responses to changes in dP/dTmax. Filled circles indicate the change in WC condition, and open squares and circles indicate the change in LC condition. a,b,cshow significant differences from rest, stage 1, and stage 2 of the same environment, respectively. *indicates a significant difference from land at the same stage.

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  Figure 5. Augmentation index (AIx) and the companion metrics of AIx (AIxC) at rest and during exercise: absolute values (top) and heart rate (HR)-corrected values via analysis of covariance (ANCOVA) (bottom). Symbols and error bars are mean and SD. The circle and square indicate water-based and land-based exercise, respectively. a,b,cshow significant differences from rest, stage 1, and stage 2 of the same environment, respectively. *indicates a significant difference from land at the same stage.