Why moderate running is good for the heart, marathon not so much

Depending on one’s point of view, the very first marathon was either a spectacular success or a deadly disaster. The legend runs that in August 490 BC, Greeks were winning The Battle of Marathon against the Persians. One of the Greek warriors, Phillipedes, noticed a Persian ship changing course towards Athens. He interpreted this to be a raid on the city while falsely claiming victory. Phillipedes ran the entire distance of approximately 42 km non-stop and burst into the legislative assembly screaming “nenikekamen” (we have won)! Next, he collapsed and died. The battle was won, the city rejoiced, many versions of the legend were spun and Phillipedes was mostly forgotten. His epic run, however, has been celebrated in prose, poetry and painting, and of course, in sport. Ever since, millions of athletes across the world have run the 42 km race in glory or defeat and sometimes in injury and death.

Marathons have gained tremendous popularity during the past two decades. The US alone has over 1000 marathons each year while in India in just under 20 years there are 500 marathons annually and counting. With their thin bodies and thick willpower, marathoners are perceived as the epitome of physical fitness and human evolution. Running preceded by bipedalism emerges as a crucial step in the saga of our species. For instance, two of the first uses of running may have been to flee from predators and pursue wounded animals while hunting. Certain features of running, such as speed and endurance, were probably essential for survival. However, running early in human evolution was vastly different from sneakers pounding concrete. The physical changes that training and racing can induce are often neither glamorous nor healthy and sometimes fatal.

About one in every 100,000 marathoners will experience cardiac arrest as an adult. However, the incidence nearly doubles during a marathon to one in every 57,000 participants. The median age of death is 41.5 years. Cardiac arrest is, however, not the only major cause of death, heat stroke is far more common. A study in 2014 identified that for every serious cardiac event, there were 10 events related to heat stroke.

There is disagreement in the research over whether running a marathon is detrimental to our heart. Several studies affirm the health benefits of marathons while others continue to oppose them. Yet, unambiguously, running in moderation is healthy. According to research published in the American College of Sports Medicine Journal, 30 minutes of running or even walking can improve a depressed mood. Another study published in the Journal of Physical Therapy Science indicates aerobic exercises lower stress hormones like cortisol and adrenaline. Running improves general blood flow providing our brains energy and oxygen which contribute to better health and enhanced mood.

A review of studies on the cognitive benefits of aerobic exercise (which included either running, jogging, or brisk walking) has shown memory, attention, and task switching as some of the benefits. Research published in the Journal of the American College of Cardiology demonstrates that running is related to significantly lower chances of death from all causes even when done just for 5 to 10 minutes per day and that too at a slow pace.

However, training for a marathon for hours at a rapid pace is not necessarily good for your heart. In the Copenhagen City Heart Study, 10,158 non-runners and 1,878 runners were tracked for up to 35 years. With a six-year improvement in life expectancy for both sexes, runners had an astounding 44 per cent decreased risk of death. However, U-shaped curves for mortality were visible in relation to the amount of running, with the benefits of running being greatest for those who jogged between 1 – 2.5 hours per week at a slow to moderate pace on average thrice a week.

Decades-long research in the US with 54,000 individuals revealed findings that were comparable. The lowest death rates were in those who ran 5 to 20 miles per week. The advantages entirely vanished at distances of 25 to 30 miles per week. Thus, excessive running may have negated the remarkably longer lifespans brought about by moderate running.

What makes running which is otherwise good for our physical health fatal? The World Health Organisation (WHO) postulates that a combination of heat, humidity and heart disease— silent or not — is a perfect storm that may be made worse by poor diet and/or a subpar fitness routine. A 2010 study found that in less fit runners, a marathon damaged the heart for up to three months. Training for a marathon creates free radicals that bond with cholesterol when it burns sugar and fat to provide energy needed for lengthy runs. After about an hour of intense exercise, the body has difficulty in handling the quantum of free radicals. This results in vulnerability to oxidative stress and cardiac dysfunction. Persistent increases in heart rate, blood pressure, cardiac output, atrial and ventricular volumes can last several hours each day in marathoners.

As more individuals engage in running, exercising caution is necessary. Prior to training, one should identify physical vulnerabilities. It is helpful to consider running as we would any effective medicine. Establishing the safe and effective range is crucial because an inappropriately low amount may not fully impart benefits while an excessive dose may result in undesirable effects that far supersede the advantages. Accomplished runners should have their medical status checked regularly. The endorphin fuelled runners high can obviate evolving injuries to the heart, knees and spine.

Pausing before take-off we could ask ourselves, if all of it is worth it at all. Perhaps, hapless Phillipedes had a greater goal beyond his life. What’s ours?

(Rajesh M. Parikh is Hon. Neuropsychiatrist and Director of Medical Research at Mumbai’s Jaslok Hospital & Research Centre. He wishes to disclose that he is not a runner and prefers long walks and treks)

#moderate #running #good #heart #marathon

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