A new twist on the cardiac response to physiological stress in humans

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Endurance training is a well-established means of enhancing cardiac function during exercise conditions. However, a paradox emerges where these adaptations appear to make endurance-trained individuals more susceptible to developing low blood pressure in response to a change in postural position (such as standing up quickly). Through a series of NSERC-funded studies we revealed that these unique responses to physiological stressors are (in part) due to a reduced interaction between the right and left sides of the heart. During this research we also made use of new cardiac imaging tools to gain an unprecedented view into the function of the right and left sides of the heart. In particular we are beginning to gain a greater understanding of the importance of the twisting and untwisting of the left side of the heart in optimal cardiac function. We have speculated that adaptations in the twisting and untwisting of the left side of the heart may be of great benefit during certain conditions (such as exercise); however these same adaptations may be detrimental under other conditions where there are sudden reductions in blood returning to the heart (such as standing up quickly). Accordingly, the proposed research program will utilize a series of novel experimental designs and methodologies to evaluate the effects of the twisting and untwisting of the left side of the heart on cardiovascular function, blood flow, and aerobic performance during diverse conditions of physiological stress. This research will have important implications for highly trained athletes and conditions that are susceptible to low blood pressure with changes in postural position (e.g., blood donation, returning from space).