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Regular participation in physical activity is well established as an important component of a comprehensive lifestyle intervention programme for primary, secondary and tertiary prevention of chronic non-communicable disease.1–3 Recreational distance running, as one form of regular physical activity, is popular globally. Data published in the 2013 Running USA Annual report indicates that there are over 50 million runners in the USA, of which >29 million run for more than 50 days/annum, and >9 million runners run for more than 110 days/annum (2013 Running USA Annual report: http://www.runningusa.org). Furthermore, almost 75% of male and female runners indicated that the main motivation to continue to run is to stay healthy. The half marathon race is the most popular event and participation in this race has also experienced the greatest growth between 2000 and 2012. Apart from the general increase in the number of runners, there is also a concomitant increase in participation in mass community-based distance running events globally. In 2012 there were more than 30 half-marathon races and more than 10 marathon races that attracted >20 000 runners (2013 Running USA Annual report: http://www.runningusa.org).
However, it is also well documented that vigorous (high intensity) physical activity, such as distance running, is associated with medical complications that can affect a variety of organ systems.4 Of particular interest is the fact that vigorous exercise may act as a trigger for cardiac arrest and sudden death as a result of acute myocardial infarction or other underlying cardiovascular diseases, in younger and older recreational athletes.5 Less well documented is the fact that, apart from acute cardiovascular complications during vigorous exercise, other serious life-threatening medical complications in other organ systems can also occur.
Therefore, on the one hand, participation in regular exercise is associated with substantial health benefits to an individual, while on the other there is an increased risk of sudden cardiac death or other serious medical complications while participating in vigorous exercise. As Sport and Exercise Medicine physicians, it is our duty to prescribe exercise for its beneficial effects to all our patients,6 but we are also charged with the responsibility to reduce the risk of any medical complications and injury during exercise, in particular life-threatening medical complications. In order to provide this care to our patients, we require accurate scientific information regarding the risk of acute medical complications during exercise and to determine, through scientific rigour, risk factors for these complications. These data would be important to provide accurate guidelines to (1) identify individuals who are at higher risk of developing complications during exercise and (2) implement and test intervention strategies to reduce the risk of medical complications during exercise.
For many years, we have been involved in providing medical service at a number of community-based mass exercise participation events, including a distance running event that is held in Cape Town on an annual basis. This event, known as the Two Oceans Marathon, comprises a number of events including a 56 km ultra marathon race, a 21 km half-marathon race, two trial running events, and a number of ‘fun’ runs. Currently, these races attract over 25 000 runners every year.
Our initial focus was to ensure the best possible medical care to athletes who present with medical complications at the medical facilities at these races. However, we noted that a number of runners with serious medical complications (and deaths) had known underlying risk factors for chronic disease. We also noted that some runners who presented with medical complications on race day reported prerace symptoms of either acute or chronic illness. Therefore, about 6 years ago, we embarked on a series of scientific studies to (1) determine the risk of acute complications during exercise in different populations, (2) identify risk factors for medical complications and (3) develop an electronic system to flag high-risk exercisers in these populations. The main purpose of these three endeavours was to design, introduce and test intervention strategies to decrease the risk of acute medical complications in exercising individuals. In this edition of BJSM, we report the results from the first three SAFER (Strategies to reduce Adverse medical events For the ExerciseR) studies in the recreational running population.
In the SAFER I study, we accurately documented all medical complications in the ultra-marathon and half-marathon runners over a 4-year period between 2008 and 2011.7 These data contribute to a currently limited body of knowledge8 on the incidence and nature of medical complications in endurance runners. In particular, our data show that there is a significant risk of serious life-threatening medical complications in ultra-marathon and half-marathon runners, and that the nature of medical complications differs in these two races. In the SAFER II and III studies we report some of the risk factors that are associated with the development of these medical complications during the ultra-marathon and half-marathon, respectively. The clinical relevance of these data is that we are now able to identify individuals that are at higher risk for medical complications during endurance running. However, as mentioned previously, we are also interested to explore our clinical observations that prerace risk factors for chronic disease or symptoms of acute or chronic illness may also contribute to increased risk of medical complications.
Therefore, as a proof of concept, we introduced a pilot study in 2011 to determine the feasibility of administering an electronic prerace medical screening and intervention system, during the Two Oceans runner registration process. In this pilot study in 2011, a self-selected sample of 2474 runners completed a prerace medical screen on a voluntary basis (response rate of 10.9%). We recognise that this pilot study is limited by selection bias, but these data indicated that 29.5% of runners who responded, reported one or more risk factors for cardiovascular disease, while 5.7% reported existing cardiovascular disease. Therefore, in this sample a significant number of the respondents were at higher risk of an acute cardiovascular complication during exercise. As race entry does not require any medical clearance, we as the medical team were particularly concerned that there are, as for most races globally, no processes in place to identify and educate runners at higher risk of an acute medical complication during running. Therefore, together with the race organisers, the prerace medical screening and intervention system became an obligatory requirement for entry to the race from 2012. In future, we will report data on the prevalence of risk factors that we obtained from this larger running population, as well as the effects of the intervention programme that we subsequently introduced to reduce the risk of medical complications during recreational running. The SAFER I, II and III studies that are published in this edition form the basis of our ongoing quest to reduce the risk of adverse medical events in these recreational exercisers.
Contributors MS was involved in writing the first draft of the manuscript and editing it. He is the guarantor. WD was involved in manuscript editing.
Funding Clinical Sport and Exercise Medicine Research Fund (partial funding), IOC Research Center (Cape Town) (partial funding).
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.