Sex differences in left ventricular function and beta-receptor responsiveness following prolonged strenuous exercise

Area of Science:

• Cardiology
• Exercise Physiology
• Endocrinology

Background:

• Sex differences in physiological responses to prolonged strenuous exercise (PSE) are established.
• Understanding cardiac function and beta-receptor responsiveness post-exercise is crucial for athlete health and performance.

Purpose of the Study:

• To investigate sex-based differences in left ventricular function.
• To examine sex-based differences in cardiac beta-receptor responsiveness following a single bout of PSE.

Main Methods:

• Nine male and eight female triathletes underwent dobutamine stress echocardiography before, immediately after, and 24 hours post-half-ironman triathlon.
• Beta-receptor responsiveness was assessed using graded dobutamine infusions, measuring heart rate and contractility changes.
• Responsiveness was quantified by the dobutamine dose required to elicit specific physiological responses.

Main Results:

• Left ventricular fractional area change decreased post-race in both sexes, with a more significant reduction in men.
• The dobutamine dose required to increase heart rate and contractility was higher post-race for both sexes.
• Men required significantly higher dobutamine doses than women to achieve these cardiac responses, indicating greater beta-receptor alterations.

Conclusions:

• Male triathletes exhibit an attenuated chronotropic and inotropic response to beta-adrenergic stimulation after PSE compared to female triathletes.
• These findings suggest greater alterations in beta-receptor function in male athletes following prolonged strenuous exercise.