Females have a blunted cardiovascular response to one year of intensive supervised endurance training

Abstract

Cross-sectional studies in athletes suggest that endurance training augments cardiovascular structure and function with apparently different phenotypes in athletic males and females. It is unclear whether the longitudinal response to endurance training leads to similar cardiovascular adaptations between sexes. We sought to determine whether males and females demonstrate similar cardiovascular adaptations to 1 yr of endurance training, matched for training volume and intensity. Twelve previously sedentary males (26 ± 7, n = 7) and females (31 ± 6, n = 5) completed 1 yr of progressive endurance training. All participants underwent a battery of tests every 3 mo to determine maximal oxygen uptake (V̇o2max) and left ventricle (LV) function and morphology (cardiac magnetic resonance imaging). Pulmonary artery catheterization was performed before and after 1 yr of training, and pressure-volume and Starling curves were constructed during decreases (lower-body negative pressure) and increases (saline infusion) in cardiac volume. Males progressively increased V̇o2max, LV mass, and mean wall thickness, before reaching a plateau from month 9 to 12 of training. In contrast, despite exactly the same training, the response in females was markedly blunted, with V̇o2max, LV mass, and mean wall thickness plateauing after only 3 mo of training. The response of LV end-diastolic volume was not influenced by sex (males +20% and females +18%). After training Starling curves were shifted upward and left, but the effect was greatest in males (interaction P = 0.06). We demonstrate for the first time clear sex differences in response to 1 yr of matched endurance training, such that the development of ventricular hypertrophy and increase in V̇o2max in females is markedly blunted compared with males.

Keywords: cardiac magnetic resonance imaging; exercise training; gender.

Fig. 1.

Average training impulse (TRIMP) scores per month in males and females. Individual sex values are presented as means ± SD.

Fig. 2.

A and B: effect of 1 yr of endurance training on maximal oxygen uptake (V̇o_2max) indexed to baseline body mass in males and females (left), significant sex × time interaction P = 0.084 and changes in left ventricle (LV) mass measured by magnetic resonance imaging (MRI) scaled to baseline fat-free mass, significant sex × time interaction P = 0.031 (right). Both measured every 3 mo during the training program. FFM, fat-free mass. Post hoc comparison with baseline (*), with month 3 (†), and with month 6 (‡) for P < 0.05 from linear mixed model.

Fig. 3.

A and B: quadratic regression analysis between average quarterly TRIMP values as measure of training stimulus and LV mass. Light gray lines, individual curves; solid black line, curves for males and females.

Fig. 4.

A and B: effect of 1 yr of endurance training on left ventricle end-diastolic volume (LVEDV, A) and right ventricle end-diastolic volume (RVEDV, B) scaled to baseline total body surface area, measured by MRI every 3 mo during the 1-yr training program. For left ventricular end-diastolic volume index (LVEDVI) and right ventricular end-diastolic volume index (RVEDVI), males and females responded in a similar manner to the training (LVEDVI sex × time P = 0.48 and RVEDVI sex × time P = 0.22).

Fig. 5.

A and B: group mean pressure-volume curves for male (A) and female (B) subjects with data points derived from baseline, lower-body negative pressure (LBNP), and rapid saline infusion, similar to Fig. 6. Each data point represents the mean ± SE of males or females, pre vs. post (sex × time P = 0.18).

Fig. 6.

A and B: group mean transmural pressure (TMP)-volume curves for male (A) and female (B) subjects with data points derived from baseline, LBNP, and rapid saline infusion. Each data point represents the mean ± SE of males or females, pre vs. post (sex × time P = 0.07).

Fig. 7.

A and B: group mean Frank-Starling curves representing pulmonary capillary wedge pressure (PCWP) as an index of LV end-diastolic pressure vs. stroke volume index (SI), over a range of LV filling produced by lower-body negative pressure (two lowest levels of PCWP), quiet baseline (two middle values of PCWP), and rapid saline infusion (two highest values of PCWP) as described in text. Each data point represents the mean ± SE of males or females, pre vs. post (sex × time P = 0.06).