Myocardial adaptation and efficiency in response to intensive physical training in elite speedskaters

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Abstract

Background

Physiological cardiac adaptations to exercise training resulting in the ‘athlete's heart’ are well known. Most of these studies, however, were included either those who exercise to exhaustion, non-elite athletes or those who participate primarily in sports requiring extensive weight training. Studies utilizing conventional and tissue Doppler echocardiographic studies in highly competitive elite athletes whose training includes both aerobic and weight training are limited.

Aims and methods

1) To identify baseline cardiovascular structural and physiologic adaptations present in elite athletes who participate in both endurance aerobic and weight training programs and to compare them to similarly aged sedentary controls. The population includes 24 speedskaters participating in the 2006 Olympic Games and 15 sedentary young subjects. 2) To evaluate possible structural and physiologic cardiac changes following short duration, vigorous exercise. We repeated the baseline echocardiographic protocol in the athletes following a 3000 m sprint conducted at race pace.

Results

Compared to non-athletes, the atrial and left ventricular (LV) volumes at rest were larger in elite athletes. There was enhanced LV diastolic function as manifested by higher early annular (septal and lateral) tissue Doppler velocities (E′): 12.7 ± 2.3 vs 11.3 ± 1.1 cm/s and 17.4 ± 4.7 vs 14.4 ± 1.2 cm/s, P = 0.025 and 0.020 respectively. Evidence of right ventricular (RV) remodeling included larger basal RV dimensions (38 ± 5 vs 32 ± 4 mm, P = 0.001), attenuated RV systolic function at rest (RV area change 35 ± 13% in athletes vs 47 ± 11% in controls, P = 0.006) and lower RV systolic strain rate (SSR) 1.9 ± 0.5 vs 2.9 ± 1.1/s, P < 0.001). However, there was better right ventricular (RV) diastolic function at rest, E′: 13.5 ± 3.6 vs 11.1 ± 1.5 cm/s (P = 0.016). Following exercise, the athletes exhibited augmentation of RV systolic function with increased RV fractional area change (increasing to 43 ± 10%, P = 0.007) and SSR (2.5 ± 1.2/s post-exercise, P = 0.038).

Conclusion

Participation by world-class speedskaters in a vigorous training regimen results in cardiovascular anatomic and physiologic adaptations. These changes, including cardiac chamber dilatation, enhanced ventricular diastolic function and attenuated resting RV systolic function, are likely adaptive and allow for more efficient energy use at rest and a robust response to demands of exercise.

Introduction

Characteristic changes of the athlete's heart include increased chamber dimensions, increased left ventricular mass, right ventricular dilatation, reduced resting right ventricular systolic function and enhanced diastolic function [1]. These features are thought to represent the physiological adaptations that occur as a result of repetitive, intense physical training [2], [3], [4], [5]. This constellation of findings in athletes can appear very similar to either hypertrophic cardiomyopathy or arrhythmogenic right ventricular dysplasia, both of which have been linked to increased risk of sudden death in athletes, therefore the ability to differentiate from these two entities is of great importance [6], [7], [8], [9]. Thus, there have been studies to differentiate between these conditions (physiological versus pathological states), though there remained some overlap using conventional parameters.

Over the last few decades, there has been vast amount of interest arising from various non-invasive studies describing the cardiac remodeling associated with different forms of exercise [10], [11] Despite this, limited information is available on highly elite athletes using novel echocardiographic assessment such as tissue Doppler imaging [12]. The evaluation of right ventricular adaptive structural and funcional changes in athletes is also lacking.

We aimed to better define anatomic and physiologic cardiac adaptations to exercise in young, highly competitive athletes whose exercise regimens include both intense aerobic and weight training. In order to increase our likelihood of identifying cardiac changes associated with training, we chose to study Olympic elite athletes training for the 2006 Winter Games. At the same time, since cardiac adaptation may be sports-specific [13], we selected speedskaters due to their intense training regimen which incorporates components of aerobic and strength or weight training. These athletes have also not been studied as extensively as other groups of athletes and their unique physiologic adaptations could possibly provide new insight. Competitive speedskating is one of the most demanding sports, as it is considered the fastest race performed by humans without the aid of a machine or relying on the surface upon which the action occurs [14]. This requires the highest components of both static and dynamic physical demands [13], [15].

Section snippets

Study population

The subjects consisted of 24 athletes (16 males and 8 females; 9 Americans, 5 Italians and 10 Chinese; aged 22 ± 3 years) and 15 sedentary young subjects (24 ± 3 years; 7 males and 8 females). All of the athletes trained intensively in preparation for the Olympic competition and performed cross-training in both sprint and endurance aerobic and strength training exercises. The sedentary subjects exercised less than 3 times a week with less than 1 h of exertion each time for at least 6 months

Baseline clinical and conventional echocardiographic parameters

The baseline characteristics of the 2 groups were similar with respect to their age, gender, body size, heart rate and blood pressures (Table 1). The left atrium was significantly larger in the athletes (3.4 ± 0.3 vs 3.0 ± 0.3 cm; 18.9 ± 2.7 vs 12.3 ± 2.0 cm2 and 33 ± 7 vs 18 ± 5 ml/m2; all P < 0.001 for anterior–posterior diameter, area and indexed volume at LV end-systole respectively). Similarly, but to a lesser extent, the LV end-diastolic and end-systolic volumes were greater in the athletes (Table 1).

Discussion

These athletes exhibit potentially important features of cardiac adaptation to regular intense physical exertion. Baseline imaging revealed that compared to similarly aged, sedentary subjects, the athletes exhibit evidence of chamber dilatation without hypertrophy. Augmented diastolic function of both the left and right ventricles as evidenced by higher tissue Doppler velocities at baseline.

Some features of classic ‘athlete's heart’ including left ventricular hypertrophy and marked left

Acknowledgements

We would like to acknowledge GE Healthcare for their equipment loan and technical support. K.K.P. is funded by the National University Hospital, National Healthcare Group, Singapore and a fellowship award from the National Medical Research Council, Singapore.

References (29)

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