The benefits of running on cardiovascular health have been widely studied and are well recognised.  Overall, runners benefit from longer lifespans and reduced mortality rates.  We have lower rates of cardiac death, hypertension, coronary artery disease, stroke, obesity, diabetes and better lipid profiles than non-runners and even experience reduced rates of deaths from non-cardiac causes, including some cancers.  These risks are lower in runners even taking account of the fact that we often have healthier lifestyles in other regards, such as better diets and lower rates of alcohol consumption.  Additional benefits of running include lower rates of depression, feeling part of the local running community, the satisfaction of achieving athletic goals and the opportunity to raise money for charity through these achievements. It is relatively cheap compared with some other sports, doesn’t require highly specialised equipment and health benefits are noticed even with relatively low levels of light jogging per week.  In general, running appears to be quite simply good for our health.  However, is all running good for us?  Recent studies suggest a detrimental impact of endurance training, which leads to the question of whether there is a level of running at which the health benefits are outweighed by the risks?

Endurance events are becoming increasingly popular.  The demographic has changed in recent years to include a higher proportion of women and the average age of participants has also increased.  Many of us are familiar with the tale of the first marathon runner, Pheidippides, who ran from Marathon to Athens in 490 BC, and died suddenly after delivering his triumphant message of victory in battle.  Pheidippides is widely acknowledged as the first documented sudden cardiac death in an endurance runner.  Sudden cardiac death is a known risk for endurance runners, with a high proportion of deaths in marathons happening in the final mile and a higher risk in males.  An emerging body of evidence suggests that the benefits of running lessen at the training levels required for marathon and ultra-marathon training.  There is evidence of an increased risk of arrhythmias (predominantly atrial fibrillation), sudden cardiac death, hypertension and even coronary artery disease for those who participate in chronic endurance running training.  However, placing this in context, the mortality rates for those engaging in endurance running training are still lower than for those who do not exercise.

The causes of the increased cardiac risks associated with chronic endurance training compared with less intense running are not well understood.  “Athletes heart” is a well-known phenomenon – those who engage in high level sporting pursuits have larger heart chambers, thickened heart muscle, changes in resting heart rate and in the electrical conduction of the heart.  Whether this is a beneficial adaptation to exercise or a maladaptive damaging process is up for debate.  It is also known that there are temporary changes in heart function and increased levels of blood markers known to be associated with heart muscle damage shortly after completing marathon distance (or longer) events, which generally normalise within one week. What is less well understood is whether these short-term effects lead to long term changes, such as scarring of the heart muscle.  How much running training is too much is a source of considerable debate.

The answer to this question is likely to be highly individual.  For example, the risk of developing atrial fibrillation (a form of abnormal heart rhythm) appears to be highest in middle aged men who have participated for many years in endurance training and continue to compete at a master’s level.  The risk is relatively low in young male athletes and risk for female endurance runners is much less well studied.  The safety of running for any individual depends on a variety of factors and running is not recommended for those with certain conditions, such as cardiomyopathy or severe aortic stenosis, as the risk profile is considered unacceptable.   Many of us are simply unwilling to consider stopping long distance running training despite the perceived risk of endurance training because of its importance in our sense of physical and mental wellbeing.  However there are some sensible steps that can be taken to mitigate risk – for example, a medical assessment prior to undertaking training for an endurance event (to produce a more personalised assessment of individual risk based on history, clinical examination and appropriate baseline investigations), stopping training and consulting a physician in the event of worrisome symptoms (including chest pain on exertion, palpitations or fainting symptoms, amongst others), incorporating appropriate rest periods into our training regimes and adopting cross-training to benefit from other forms of exercise. In conclusion, running overall has excellent health benefits, both in terms of cardiovascular disease and general mortality risk.  These advantages can be appreciated even with relatively low intensity and frequency running training.  From a pure cardiovascular risk perspective, the cardiovascular health benefits of running are best in those training for shorter events, such as 5- and 10-kilometre races and lessen with increasing training volumes.  At the extremes of endurance training, there are some increased risks which those who choose to participate in this type of event should consider and weigh up.  If a person has a high risk personal or family history or has symptoms which may relate to running training, then they should consult a medical professional to determine the risk: benefit profile of continuing with this form of training.