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

Abstract

Sex differences in neuroendocrine and metabolic responses to prolonged strenuous exercise (PSE) have been well documented. The aim of this investigation was to examine sex differences in left ventricular function and cardiac beta-receptor responsiveness following a single bout of PSE. Nine male and eight female triathletes were examined during three separate sessions: before, immediately after, and 24 h following a half-ironman triathlon using dobutamine stress echocardiography. Steady-state graded infusions of dobutamine were used to assess beta-receptor responsiveness. Slopes calculated from linear regressions between dobutamine doses and changes in heart rate and contractility for each participant were used as an index of beta-receptor responsiveness. Despite no change in preload, fractional area change decreased from baseline after the race in both men and women, with a greater decrease in men [men: 54.1% (SD 2.1) to 50.7% (SD 3.4) vs. women: 55.4% (SD 2.7) to 53.3% (SD 2.5); P < 0.05]. The amount of dobutamine necessary to increase heart rate by 25 beats/min [men: 29.6 microg x kg(-1) x min(-1) (SD 6.6) to 42.7 microg x kg(-1) x min(-1) (SD 12.9) vs. women: 23.5 microg x kg(-1) x min(-1) (SD 4.0) to 30.0 microg x kg(-1) x min(-1) (SD 7.8); P < 0.05] and contractility by 10 mmHg/cm2 [men: 20.9 microg x kg(-1) x min(-1) (SD 5.1) to 37.0 microg x kg(-1) x min(-1) (SD 11.5) vs. women: 22.6 microg x kg(-1) x min(-1) (SD 6.4) to 30.7 microg x kg(-1) x min(-1) (SD 7.2); P < 0.05] was greater in both men and women postrace. However, the amount of dobutamine required to induce these changes was greater in men, reflecting larger beta-receptor alterations in male triathletes following PSE relative to women. These data suggest that following an acute bout of PSE, male triathletes demonstrate an attenuated chronotropic and inotropic response to beta-adrenergic stimulation compared with female triathletes.

Impaired left and right ventricular function following prolonged exercise in young athletes: influence of exercise intensity and responses to dobutamine stress

“…Our subject population included both male and female participants. In contrast to one previous study (36), we found no significant sex differences in our primary indexes for systolic and diastolic function, allowing for a single-group analysis with sexes combined.…”

“…A reduction in ␤-adrenergic sensitivity following PE has been reported by others (12,19,36,37,42); however, this is the first study to examine the contribution of exercise intensity and NA to this phenomenon. Data from animal chronic pacing studies (i.e., duration: 3 h to 20 days) have demonstrated significant reductions in ventricular function (1, 25, 44), secondary to reductions in ␤-adrenergic sensitivity and density (31, 35, 44).…”

“…Recent studies have utilized speckle tracking (15, 32) to enable less load-dependent estimations of contractility, overcoming many previous echocardiographic (Echo) limitations (2,26,29). While the intrinsic physiological mechanism leading to transient impairments in cardiac function remains unclear, ␤-adrenergic receptor saturation with elevated catecholamine levels [i.e., noradrenaline (NA)] during PE has been hypothesized to produce reductions in ␤-adrenergic receptor sensitivity and myocardial contractility (15,17,36,42); however, ␤-adrenergic desensitization following PE has not been assessed in conjunction with speckle trackingbased measures of myocardial strain (S) and strain rate (SR). The influence of exercise intensity on the development of EICF has not been examined directly, yet field studies typically include subjects who may complete distance events under widely disparate times, corresponding to a wide range in exercising heart rates (HRs).…”

“…The influence of exercise intensity on the development of EICF has not been examined directly, yet field studies typically include subjects who may complete distance events under widely disparate times, corresponding to a wide range in exercising heart rates (HRs). This may be associated with differing catecholamine release, which may ultimately increase the magnitude of ␤-adrenergic desensitization (4,5,36,45). Therefore, the purpose of this study was to examine the effects of both moderate-and high-intensity exercise on LV and RV performance during and following PE.…”

Cardiac Effects of Exercise Training in Hypertension

“…Interestingly, a study by Scott et al showed that postexercise AR responsiveness was maintained in women to a greater extent than men following exhaustive exercise. is is a signi�cant �nding given that postexercise AR desentization is hypothesized to be an element of cardiac dysfunction aer acute, exhaustive exercise [112].…”