Young athlete's growing heart: sex differences in cardiac adaptation to exercise training during adolescence

Abstract

Background: Athlete's heart is a condition of exercise-induced cardiac remodelling. Adult male endurance athletes more often remodel beyond reference values. The impact of sex on remodelling through adolescence remains unclear. Paediatric reference values do not account for patient sex or exercise history. We aimed to study the effect of sex on cardiac remodelling throughout adolescence.

Methods: We recruited 76 male (M) and female (F) 12-year-old cross-country skiers in a longitudinal cohort study. Echocardiography was performed and analysed according to guidelines at age 12 (48 M, 28 F), 15 (34 M, 14 F) and 18 (23 M, 11 F). Repeated echocardiographic measurements were analysed by linear mixed model regression.

Results: Males displayed greater indexed left ventricular end-diastolic volumes (LV EDVi) from age 12 (M 81±7 vs F 76±7, mL/m², p≤0.01), and progressed further until follow-up at age 18 (M 2.3±9.7 vs F -3.9±4.5 ΔmL/m², p≤0.01). LV EDVi remained above adult upper reference values in both groups. Males increased LV Mass Index from age 12 to 18 (M 33±27 vs F 4±19, Δg/m², p≤0.01). Males displayed LV mass above paediatric reference values at ages 15 and 18. A subset of males (35%) and females (25%) displayed wall thickness above paediatric reference values at age 12. Cardiac function was normal. There was no sex difference in exercise hours.

Conclusion: Sex-related differences in athlete's heart were evident from age 12, and progressed throughout adolescence. Remodelling beyond reference values was more frequent than previously reported, particularly affecting males. Age, sex and exercise history may assist clinicians in distinguishing exercise-induced remodelling from pathology in adolescents.

Keywords: CARDIAC REMODELLING; Cardiac Imaging Techniques; Echocardiography.

Figure 1

Flow chart. Number of male (blue panel) and female (red panel) participants at baseline, first and second follow-up.

Figure 2

Illustration of typical sex differences in LV remodelling in adolescent athletes by echocardiography. Typical LV remodelling (at end-diastole) from apical four-chamber view in a male (upper row) and a female (lower row) adolescent athlete. The male athlete displays greater increase in LV EDV, LV EDVi and LVMI compared with the female from age 12 (first column), to age 15 (second column) and age 18 (third column). EDV(i), end-diastolic volume (indexed); LV, left ventricular; LVMI; LV mass indexed.

Figure 3

Distribution of left ventricular mass (LVM) Z-scores in serial echocardiographic measurements of male and female adolescent athletes at ages 12, 15 and 18. Males in blue (upper row), females in red (lower row). The orange, verticle line demarks Z-score 2. Values to the right of the orange line are above upper reference value. P values comparing male and female group at baseline (age 12) are calculated using the Student’s t-test, and not significant (NS). P values for follow-ups (ages 15 and 18) are calculated by linear mixed model regression analysis.