Marathon Run: Cardiovascular Adaptation and Cardiovascular Risk

Hans-Georg Predel

Disclosures

Eur Heart J. 2014;35(44):3091-3098. 

In This Article

Abstract and Introduction

Abstract

The first marathon run as an athletic event took place in the context of the Olympic Games in 1896 in Athens, Greece. Today, participation in a 'marathon run' has become a global phenomenon attracting young professional athletes as well as millions of mainly middle-aged amateur athletes worldwide each year. One of the main motives for these amateur marathon runners is the expectation that endurance exercise (EE) delivers profound beneficial health effects. However, with respect to the cardiovascular system, a controversial debate has emerged whether the marathon run itself is healthy or potentially harmful to the cardiovascular system, especially in middle-aged non-elite male amateur runners. In this cohort, exercise-induced increases in cardiac biomarkers—troponin and brain natriuretic peptide—and acute functional cardiac alterations have been observed and interpreted as potential cardiac damage. Furthermore, in the cohort of 40- to 65-year-old males engaged in intensive EE, a significant risk for the development of atrial fibrillation has been identified. Fortunately, recent studies demonstrated a normalization of the cardiac biomarkers and the functional alterations within a short time frame. Therefore, these alterations may be perceived as physiological myocardial reactions to the strenuous exercise and the term 'cardiac fatigue' has been coined. This interpretation is supported by a recent analysis of 10.9 million marathon runners demonstrating that there was no significantly increased overall risk of cardiac arrest during long-distance running races. In conclusion, intensive and long-lasting EE, e.g. running a full-distance Marathon, results in high cardiovascular strain whose clinical relevance especially for middle-aged and older athletes is unclear and remains a matter of controversy. Furthermore, there is a need for evidence-based recommendations with respect to medical screening and training strategies especially in male amateur runners over the age of 35 years engaged in regular and intensive EE.

Introduction

Inspired by the ancient run from Marathon to Athens 490 BC, the idea to revive this long-distance run was born in the context of the first modern Olympic Games in 1896 taking place in Athens, Greece. While this first marathon run of modern times had a distance of ~40 km today's official distance of 42.195 km was established with the marathon run of the Olympic Games in London 1908[1] (Table 1). In recent decades, participation in a 'marathon run' has become increasingly attractive for millions of non-professional endurance athletes worldwide each year. Regarding the cohort of athletes participating in city-marathon events, there are only a small number of high-performance professional athletes aged between 18 and 35 years. These athletes are generally healthy, continuously medically supervised, and supported by experienced trainers. In contrast, the number of non-elite recreational marathon runners, including individuals of all age groups, is continuously rising. Indeed, the athletic and demographical characteristics of marathon runners are rapidly changing. According to a demographical analysis of these amateur athletes, the majority are middle-aged male amateur runners competing at amazing performance levels.[2] For example, the winning time of the marathon run of the Olympic Games in 1936 was matched by the running time of the best M55 amateur runner of the 2012 Berlin marathon.[3] These aspects are of special importance since several studies revealed that middle-aged amateur runners frequently exhibit a cardiovascular risk profile, which is typical for their age group.[2,4,5]

Meanwhile, it is well known and widely accepted that regular and moderate physical activity (PA) has beneficial effects on nearly all biological structures and functions of the human body, including the cardiopulmonary system (Table 2). With respect to the ideal dose of endurance PA, the Harvard Alumni Study demonstrated an optimal cardiovascular health effect by an additional energy consumption of 2000–3000 kcal/week or 300–400 kcal/day.[6,7] Even moderate amounts of regular PA (~15 min per day) are associated with significant preventive effects towards a variety of diseases, e.g. diabetes, cancer, and cardiovascular events,[8] but also prolonging life expectancy.[9,10] However, concerning beneficial health effects, it is difficult to define the optimal individual amount of endurance exercise (EE) as well as the upper 'dose-limit' on the basis of currently available studies. Nevertheless, regarding certain cardiovascular diseases, such as atrial fibrillation (AF), there are indications about potential 'overdoses' of EE.[11] In this context, in a case–control study, Elosua et al.[12] identified a threshold of more than 1500 lifetime hours of exercising. Furthermore, Möhlenkamp et al.[5] observed a relatively high coronary artery calcification (CAC) burden in presumably healthy male athletes (>55 years old) who had performed at least five marathon runs during the previous 3 years. Taking these considerations into account, regular EE at moderate doses and intensities is recommended for the prevention of cardiovascular diseases by international guidelines (Figure 1).[13–16]

Figure 1.

Potential association between dose of endurance sports and cardiovascular events (modified from La Gerche et al.38).

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