ER had larger unadjusted LV wall and chamber dimensions, LV mass, left atrial volumes, and RV dimensions than SR (Table 2). After adjustment for BSA, LV and RV chamber dimensions and LV mass remained significantly higher in ER than that in SR. In contrast, BSA adjustment eliminated the differences in left atrial size and LV wall thickness.
LV ejection fraction and peak LV systolic strain were similar in ER and SR. In contrast, peak systolic tissue velocities in both the basal interventricular septum and the basal lateral LV wall were higher in ER. Stroke volume, regardless of adjustment for BSA, remained higher in ER than that in SR. RV systolic function, as measured by fractional area change, peak systolic tissue velocity, and peak systolic strain, was higher in ER than SR.
Physiologic cardiac remodeling in response to both static and dynamic exercise training is well recognized. Careful inspection of previously published data defining this phenomenon reveals the presence of significant variability among athletes. Although several variables including athlete gender, ethnicity, sport/training type, age, and genetic profile have been shown to contribute to this variability, no single factor or combination of factors appears to explain all of the observed interindividual variability. Although the magnitude of most physiologic adaptation and maladaptation is related to the degree of the stimulus responsible for the change, little is known about the dose-response relationship between exercise training and cardiac remodeling. To begin to address this area of uncertainty, we compared two groups of rowers (ER and SR) with significant differences in both short-term training volume and cumulative years of competitive rowing experience to one another and to sedentary controls.
Our findings can be summarized as follows. First, almost all cardiac parameters in ER and SR differed from those observed in sedentary controls, suggesting that significant cardiac remodeling was present in rower groups at both competition levels. Second, ER possessed larger LV chambers, LV mass, and RV chambers than SR even when chamber dimensions were adjusted for BSA. It is noteworthy that adjustment for BSA eliminated the difference in LV wall thickness between ER and SR. Thus, the greater LV mass observed in ER was attributable to their relative larger LV chamber volumes. Third, resting RV systolic function, as assessed by several complimentary indices, was more enhanced in ER than that in SR. This finding is of particular interest given the fact that the RV's importance as a determinant of peak exercise capacity remains uncertain. Finally, ER demonstrated a marked enhancement of late diastolic filling in both ventricles when compared with SR.
The finding that rowing competition level is associated with specific cardiac attributes has two plausible explanations. First, the relative biventricular chamber enlargement, RV systolic function enhancement, and maximally efficient late diastolic filling may be innate characteristics of ER that predate exercise training and thus provide a selective advantage to perform at the highest level of this sport. Although prior data from childhood high-performers does not suggest that innate cardiac phenotype dictates success at a young age (24,25,33,34,38), longitudinal studies characterizing cardiac structure from childhood through to the adulthood time of peak performance are needed to address this possibility. The second and more likely explanation is that the characteristic findings in ER may be a direct function of the amount of exercise training, both in the short-term and over cumulative years, to which these individuals are exposed. Several recent longitudinal studies demonstrating similar adaptations in rowers support this hypothesis (2,8). Further, long-term study, with a specific focus on the underlying cellular mechanisms that dictate myocardial remodeling in response to cumulative exercise exposure, is needed.
This study is the first to document the relationship between competition level and cardiac parameters in a direct comparative fashion. This finding has important implications with relevance to the clinical care of athletes and to the future exercise physiology research. For the clinician faced with differentiating healthy physiologic cardiac remodeling from that secondary to underlying disease, we provide clear evidence that competition level should be factored into the list of clinical variables currently recommended for this purpose (19). Further, our data clearly demonstrate that the majority of both elite and subelite rowers and likely similar caliber athletes from other endurance-based sports possess cardiac structural and functional values that fall far outside the range of what is currently considered normal (15). This finding underscores the need for the collaboration of the cardiovascular and sports medicine communities to establish data-driven reference ranges of normal for trained athletes. Our findings also provide the framework for future studies aimed at determining which cardiovascular parameters serve as important determinants of exercise capacity (17,18). Confirmation of our findings coupled with definitive assessments of exercise capacity will lead to an improved understanding of how the heart and the circulatory system contribute to performance potential.
There are several limitations of this study. As previously addressed, the cross-sectional nature of our study design does not afford the opportunity to fully establish the causality of our observations. Although prior work suggests that our findings represent adaptation to variable volumes of exercise training, we cannot confirm that all of our observations can be explained simply by group differences in exercise exposure. Second, because all measurements were made with the athletes at rest and we were logistically unable to perform exercise capacity testing, we are unable to draw definitive conclusion about how our observations relate to cardiac function during exercise or to measures of exercise capacity. Third, as this study used athletes in real-world training environments, we were unable to characterize exercise training intensity using any of the usual quantitative metrics (exercise heart rate, power output, or percentage of peak oxygen consumption) during the period before study. Although our quantification of training volume (h·wk−1) demonstrated a "dose-dependent" relationship between cardiac remodeling and exercise training, our data do not permit us to determine whether group differences in exercise training intensity may have contributed to our observations. Finally, as ER had trained more (h·wk−1) in the immediate period before assessment and had accumulated more long-term rowing experience (yr) than SR, we are unable to draw definitive conclusions about the relative contribution of short- versus long-term training to the observed differences. Future work is warranted to determine which aspects of exercise training and sport participation are responsible for the competition level-associated differences we observed.
In conclusion, we present novel data documenting significant differences in cardiac structure and function between elite, Olympic caliber, and subelite university-level rowers. ER were found to have larger biventricular dimensions and greater enhancement of both RV systolic function and biventricular diastolic function than SR. These findings demonstrate that competition level is strongly associated with underlying heart structure and function and that this factor should be considered in both the clinical care and the future study of athletes.
The authors wish to acknowledge Jennifer Neary, R.D.C.S., Carlene McClanahan, R.D.C.S., and Tricia Eshelman, R.D.C.S., for their expertise with echocardiographic data acquisition. The results of the present study do not constitute endorsement by the American College of Sports Medicine.
1. Anavekar NS, Gerson D, Skali H, Kwong RY, Kent Yucel E, Solomon SD. Two-dimensional assessment of right ventricular function: an echocardiographic-MRI correlative study. Echocardiography
2. Baggish AL, Wang F, Weiner RB, et al. Training-specific changes in cardiac structure and function: a prospective and longitudinal assessment of competitive athletes. J Appl Physiol
3. Baggish AL, Weiner RB, Yared K, et al. Impact of family hypertension history on exercise-induced cardiac remodeling
. Am J Cardiol
4. Baggish AL, Yared K, Wang F, et al. The impact of endurance exercise training on left ventricular systolic mechanics. Am J Physiol
5. Basavarajaiah S, Boraita A, Whyte G, et al. Ethnic differences in left ventricular remodeling in highly-trained athletes relevance to differentiating physiologic left ventricular hypertrophy from hypertrophic cardiomyopathy. J Am Coll Cardiol
6. George KP, Gates PE, Birch KM, Campbell IG. Left ventricular morphology and function in endurance-trained female athletes. J Sports Sci
7. Goodman JM, Liu PP, Green HJ. Left ventricular adaptations following short-term endurance training. J Appl Physiol
8. Haykowsky M, Chan S, Bhambhani Y, Syrotuik D, Quinney H, Bell G. Effects of combined endurance and strength training on left ventricular morphology in male and female rowers. Can J Cardiol
9. Henriksen E, Landelius J, Kangro T, et al. An echocardiographic study of right and left ventricular adaptation to physical exercise in elite female orienteers. Eur Heart J
10. Hernandez D, de la Rosa A, Barragan A, et al. The ACE/DD genotype is associated with the extent of exercise-induced left ventricular growth in endurance athletes. J Am Coll Cardiol
11. Hoogsteen J, Hoogeveen A, Schaffers H, Wijn PF, van der Wall EE. Left atrial and ventricular dimensions in highly trained cyclists. Int J Cardiovasc Imaging
12. Kemi OJ, Haram PM, Loennechen JP, et al. Moderate vs. high exercise intensity: differential effects on aerobic fitness, cardiomyocyte contractility, and endothelial function. Cardiovasc Res
13. Kemi OJ, Haram PM, Wisloff U, Ellingsen O. Aerobic fitness is associated with cardiomyocyte contractile capacity and endothelial function in exercise training and detraining. Circulation
14. Konhilas JP, Widegren U, Allen DL, Paul AC, Cleary A, Leinwand LA. Loaded wheel running and muscle adaptation in the mouse. Am J Physiol
15. Lang RM, Bierig M, Devereux RB, et al. Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr
16. Lee IM, Sesso HD, Oguma Y, Paffenbarger RS Jr. Relative intensity of physical activity and risk of coronary heart disease. Circulation
17. Legaz Arrese A, Munguia Izquierdo D, Serveto Galindo JR. Physiological measures associated with marathon running performance in high-level male and female homogeneous groups. Int J Sports Med
18. Legaz Arrese A, Serrano Ostariz E, Gonzalez Carretero M, Lacambra Blasco I. Echocardiography to measure fitness of elite runners. J Am Soc Echocardiogr
19. Maron BJ, Pelliccia A. The heart of trained athletes: cardiac remodeling and the risks of sports, including sudden death. Circulation
20. Montgomery HE, Clarkson P, Dollery CM, et al. Association of angiotensin-converting enzyme gene I/D polymorphism with change in left ventricular mass in response to physical training. Circulation
21. Morganroth J, Maron BJ, Henry WL, Epstein SE. Comparative left ventricular dimensions in trained athletes. Ann Intern Med
22. Nagueh SF, Middleton KJ, Kopelen HA, Zoghbi WA, Quinones MA. Doppler tissue imaging: a noninvasive technique for evaluation of left ventricular relaxation and estimation of filling pressures. J Am Coll Cardiol
23. Naylor LH, Arnolda LF, Deague JA, et al. Reduced ventricular flow propagation velocity in elite athletes is augmented with the resumption of exercise training. J Physiol
. 2005;563(Pt 3):957-63.
24. Obert P, Mandigout S, Vinet A, N'Guyen LD, Stecken F, Courteix D. Effect of aerobic training and detraining on left ventricular dimensions and diastolic function
in prepubertal boys and girls. Int J Sports Med
25. Obert P, Mandigouts S, Nottin S, Vinet A, N'Guyen LD, Lecoq AM. Cardiovascular responses to endurance training in children: effect of gender. Eur J Clin Invest
26. Pelliccia A, Avelar E, De Castro S, Pandian N. Global left ventricular shape is not altered as a consequence of physiologic remodeling in highly trained athletes. Am J Cardiol
. 2000;86(6):700-2, A9.
27. Pelliccia A, Culasso F, Di Paolo FM, Maron BJ. Physiologic left ventricular cavity dilatation in elite athletes. Ann Intern Med
28. Pelliccia A, Maron BJ, Culasso F, Spataro A, Caselli G. Athlete's heart
in women. Echocardiographic characterization of highly trained elite female athletes. JAMA
29. Pelliccia A, Maron BJ, Di Paolo FM, et al. Prevalence and clinical significance of left atrial remodeling in competitive athletes. J Am Coll Cardiol
30. Pelliccia A, Maron BJ, Spataro A, Proschan MA, Spirito P. The upper limit of physiologic cardiac hypertrophy in highly trained elite athletes. N Engl J Med
31. Pluim BM, Zwinderman AH, van der Laarse A, van der Wall EE. The athlete's heart
: a meta-analysis of cardiac structure and function. Circulation
32. Prasad A, Popovic ZB, Arbab-Zadeh A, et al. The effects of aging and physical activity on Doppler measures of diastolic function
. Am J Cardiol
33. Rowland T, Goff D, Popowski B, DeLuca P, Ferrone L. Cardiac responses to exercise in child distance runners. Int J Sports Med
34. Rowland T, Wehnert M, Miller K. Cardiac responses to exercise in competitive child cyclists. Med Sci Sports Exerc
35. Scharhag J, Schneider G, Urhausen A, Rochette V, Kramann B, Kindermann W. Athlete's heart
: right and left ventricular mass and function in male endurance athletes and untrained individuals determined by magnetic resonance imaging. J Am Coll Cardiol
36. Sharma S, Maron BJ, Whyte G, Firoozi S, Elliott PM, McKenna WJ. Physiologic limits of left ventricular hypertrophy in elite junior athletes: relevance to differential diagnosis of athlete's heart
and hypertrophic cardiomyopathy. J Am Coll Cardiol
37. Tanasescu M, Leitzmann MF, Rimm EB, Willett WC, Stampfer MJ, Hu FB. Exercise type and intensity in relation to coronary heart disease in men. JAMA
38. Telford RD, McDonald IG, Ellis LB, Chennells MH, Sandstrom ER, Fuller PJ. Echocardiographic dimensions in trained and untrained 12-year-old boys and girls. J Sports Sci
39. Whyte G, Sharma S, George K, McKenna WJ. Alterations in cardiac morphology and function in elite multi-disciplinary athletes. Int J Sports Med
40. Zoncu S, Pelliccia A, Mercuro G. Assessment of regional systolic and diastolic wall motion velocities in highly trained athletes by pulsed wave Doppler tissue imaging. J Am Soc Echocardiogr