Words by Peta Bee
There has never been much doubt that running is one of the best forms of exercise for the heart. Its unrivalled ability to enhance cardiovascular fitness means you are strengthening both your heart and lungs with each stride you take. Studies have proven that runners live longer and enjoy healthier lives than non-exercisers, which is mainly due to these heart-boosting benefits. Yet fatal heart attacks do occur during distance races.
At an international conference on marathon medicine, held at the Royal Society of Medicine earlier this year, experts revealed that endurance runners do have elevated levels of the hormone brain natriuretic peptide – a red flag for cardiac dysfunction – and cardiactroponin, a chemical that shows up in blood tests only when the heart muscle is damaged. One sports scientist, Dr Rob Shave, of Brunel University, says that 58 per cent of London Marathon finishers have levels of cardiac troponin so high, cardiologists would assume they’d been admitted to hospital for heart attacks.
However, experts like Dr Shave now think the presence of such high levels of chemicals after a long-distance run is not permanently damaging. “There’s no doubt that some damage occurs to the heart,” says Shave. “But the latest thinking is that the heart – being a muscle – responds by growing even stronger after an endurance test, so the ultimate response could be positive.” So, if the chemicals produced as a result of running ultimately repair and strengthen the heart, what causes these marathon and half-marathon deaths? One cause is likely to be Sudden Death Syndrome (SDS), a condition that kills up to 12 young people a week in the UK, making it the most common cause of unexpected death in people under 35. Although running doesn’t cause SDS, high-intensity sports can trigger it – the strain placed on the heart during intense physical activity can prove too much when there is already an underlying heart problem. “There are different types of heart abnormalities that can lead to the syndrome, the most common being hypertrophic cardiomyopathy,” says Alison Cox, founder of the charity Cardiac Risk in the Young (CRY). “It makes the heart thicken, leads to an irregular heartbeat and stops the heart pumping effectively.” Cox says screening tests are available, but are not compulsory.
One such problem that could be identified is a cardiac arrhythmia caused by the genetic condition, long QT syndrome. Dr Michael Ackerman, a cardiologist at the Windland Smith Rice Sudden Death Genomics Laboratory at the Mayo Clinic, Minnesota, says about one in 2,000 people are born with a condition that can cause a blip in the heart’s wiring, with long QT syndrome being the most common. “In someone with long QT syndrome, the heart is sluggish between beats and these delayed intervals can give rise to skipped beats,” Dr Ackerman says. “When that happens, the heart’s electrical system can go so badly off course that it leads to a potentially fatal arrhythmia.”
Feel the beat
What cardiologists and sports scientists are certain about, however, is that while running and other sports might make a susceptible person more vulnerable to heart attacks, the activity itself is rarely the root of the problem. “Running prevents far more deaths than it causes,” says Louise Sutton, head of the Carnegie Centre for Sports Performance and Wellbeing at Leeds Metropolitan University. “In most cases, deaths during or after a run are the result of an underlying abnormality. Running is more likely to prolong your life than cut it short.”
Heart health and hot weather
As well as not being very comfortable, increased sweat loss and insufficient fluid intake while running in hot weather may increase the risk of hyperthermia and heat injury, which puts a strain on the body’s organs, including the heart. Wearing fancy dress during a race to raise money for charity also increases the likelihood of heat stress, by impairing your ability to cool down. Dr Hilary Ann Peterson, an expert in emergency medicine at the University of Arkansas School of Medical Sciences, has studied post extreme endurance syndrome (PEES) and says that runners, especially those who are less than optimally fit or who overexert themselves, could damage muscle fibres because of an excessive build-up of potassium in the blood. To reduce? your risk in warm conditions, clothing should be light – in fact, the less worn the better. If you suffer from dizziness, a headache, or feel faint, very hot or very cold while running, you should call it a day. As Peterson says, “Your body tells you when it’s had enough. Listen to it.”