Left Ventricular Mechanics in Runners vs. Bodybuilders
We aimed to compare two very different sport disciplines in terms of myocardial mechanics: highly trained marathon runners and bodybuilders. While conventional echocardiographic parameters failed to be different between the two groups, speckle tracking derived strain indices showed a different pattern of deformation compared to each other and to healthy controls as well.
The multiple helical fiber orientation of the LV is a well known phenomenon, however, the contribution of separate deformation directions to LV performance is a novel field of interest. Longitudinal strain refers to the shortening of the LV in long-axis (negative value), and has become a valuable clinical parameter which reflects numerous pathological conditions (i.e. ischemia) sensitively. Circumferential strain can be interpreted by a short-axis shortening of the myofibers (negative value) and has been shown to be the major deformation direction generating ejection. Radial thickening on a short-axis image is a summation of other deformation directions, which can be quantified by radial strain (positive value). Different pathologies can alter uniquely this deformation pattern, therefore we hypothesized that sport disciplines with divergent exercise nature can also result in different adaptation regarding myocardial mechanics.
Athlete's heart is characterized by a physiological increase in LV mass. A classical hypothesis suggests that sports with mainly endurance exercise nature (long-distance running, cycling, etc.) result in excentric LV hypertrophy, while power sports (weightlifting) induce concentric hypertrophy. However, the spectrum of athlete's heart is very broad and substantive investigation of the adaptation induced by mostly endurance or power training is difficult. Therefore, we selected our study population to address this issue. Long-distance running is a good example of clear endurance training, while the goal of bodybuilders is completely different with weightlifting: to provide spectacular outlook and huge amount of muscle mass. To date, no study has investigated this two very popular sports head-to-head.
In contrast to our expectations, the groups of athletes were similar to each other regarding morphological features provided by echocardiography. Furthermore, conventional parameters of LV systolic function (ejection fraction, S' by tissue Doppler imaging) also failed to distinguish between the two types of athlete's heart.
The novel method of speckle tracking echocardiography allows us to easily characterize myocardial mechanics on standard two-dimensional grey-scale images. We found that longitudinal strain is lower in endurance athletes, while this decrease correlated with the increase in LV end-diastolic volume and also body surface area. These associations can be explained by the phenomenon of a larger LV that needs less deformation to maintain stroke volume during resting conditions. Furthermore, lower baseline strain values with preserved ejection fraction may also imply a possible functional reserve capacity and could be a sign of a trained heart. On the contrary, Simsek and coworkers found increased longitudinal strain in athletes while comparing eccentric and concentric types of LV hypertrophy. The possible explanation can be the significantly lower age of their population, as the age-related decrease of longitudinal strain has been reported. It also highlights the issue of proper selection of the athletes' groups which can lead to the interpretation of inconsistent results in the literature.
In bodybuilders the circumferential strain was found to be lower. In this group, the decrease in circumferential shortening strongly correlated with increased LV mass. The relationship between increased LV mass and decreased strain values is well-known from previous studies involving patients with hypertrophic cardiomyopathy, aortic stenosis, and also with hypertension-induced hypertrophy. Based on this and also on the correlation between systolic blood pressure and circumferential strain values in bodybuilders, suspicion of pathological remodelling may be reasonable despite our study design was remarkably aimed to exclude arterial hypertension in advance. Thus, our results better represent preliminary, cross-sectional data, as we are following-up our athletes regularly and looking for further clinical relevance of the strain parameters.
In-depth analysis of myocardial mechanics raises the question whether strain parameters could be able to differentiate pathological and physiological remodelling and maybe could help to monitor the training phases of an athlete. Promising data are available regarding a classical dilemma of sports medicine: differentiation between hypertrophic cardiomyopathy and athlete's heart. Nevertheless, if we would like to use speckle tracking to help sport-specific training we have to understand the deformation profile of a given discipline. Aiming that, larger studies are needed, however, our data may help to highlight this issue.
Discussion
We aimed to compare two very different sport disciplines in terms of myocardial mechanics: highly trained marathon runners and bodybuilders. While conventional echocardiographic parameters failed to be different between the two groups, speckle tracking derived strain indices showed a different pattern of deformation compared to each other and to healthy controls as well.
The multiple helical fiber orientation of the LV is a well known phenomenon, however, the contribution of separate deformation directions to LV performance is a novel field of interest. Longitudinal strain refers to the shortening of the LV in long-axis (negative value), and has become a valuable clinical parameter which reflects numerous pathological conditions (i.e. ischemia) sensitively. Circumferential strain can be interpreted by a short-axis shortening of the myofibers (negative value) and has been shown to be the major deformation direction generating ejection. Radial thickening on a short-axis image is a summation of other deformation directions, which can be quantified by radial strain (positive value). Different pathologies can alter uniquely this deformation pattern, therefore we hypothesized that sport disciplines with divergent exercise nature can also result in different adaptation regarding myocardial mechanics.
Athlete's heart is characterized by a physiological increase in LV mass. A classical hypothesis suggests that sports with mainly endurance exercise nature (long-distance running, cycling, etc.) result in excentric LV hypertrophy, while power sports (weightlifting) induce concentric hypertrophy. However, the spectrum of athlete's heart is very broad and substantive investigation of the adaptation induced by mostly endurance or power training is difficult. Therefore, we selected our study population to address this issue. Long-distance running is a good example of clear endurance training, while the goal of bodybuilders is completely different with weightlifting: to provide spectacular outlook and huge amount of muscle mass. To date, no study has investigated this two very popular sports head-to-head.
In contrast to our expectations, the groups of athletes were similar to each other regarding morphological features provided by echocardiography. Furthermore, conventional parameters of LV systolic function (ejection fraction, S' by tissue Doppler imaging) also failed to distinguish between the two types of athlete's heart.
The novel method of speckle tracking echocardiography allows us to easily characterize myocardial mechanics on standard two-dimensional grey-scale images. We found that longitudinal strain is lower in endurance athletes, while this decrease correlated with the increase in LV end-diastolic volume and also body surface area. These associations can be explained by the phenomenon of a larger LV that needs less deformation to maintain stroke volume during resting conditions. Furthermore, lower baseline strain values with preserved ejection fraction may also imply a possible functional reserve capacity and could be a sign of a trained heart. On the contrary, Simsek and coworkers found increased longitudinal strain in athletes while comparing eccentric and concentric types of LV hypertrophy. The possible explanation can be the significantly lower age of their population, as the age-related decrease of longitudinal strain has been reported. It also highlights the issue of proper selection of the athletes' groups which can lead to the interpretation of inconsistent results in the literature.
In bodybuilders the circumferential strain was found to be lower. In this group, the decrease in circumferential shortening strongly correlated with increased LV mass. The relationship between increased LV mass and decreased strain values is well-known from previous studies involving patients with hypertrophic cardiomyopathy, aortic stenosis, and also with hypertension-induced hypertrophy. Based on this and also on the correlation between systolic blood pressure and circumferential strain values in bodybuilders, suspicion of pathological remodelling may be reasonable despite our study design was remarkably aimed to exclude arterial hypertension in advance. Thus, our results better represent preliminary, cross-sectional data, as we are following-up our athletes regularly and looking for further clinical relevance of the strain parameters.
In-depth analysis of myocardial mechanics raises the question whether strain parameters could be able to differentiate pathological and physiological remodelling and maybe could help to monitor the training phases of an athlete. Promising data are available regarding a classical dilemma of sports medicine: differentiation between hypertrophic cardiomyopathy and athlete's heart. Nevertheless, if we would like to use speckle tracking to help sport-specific training we have to understand the deformation profile of a given discipline. Aiming that, larger studies are needed, however, our data may help to highlight this issue.
SHARE
