Taking a risk in the long run

RUNNING MARATHONS is quite popular – more than 12,500 runners took part in the Dublin City Marathon on October 26th. It is generally thought that popular marathon-running is a healthy development, but I cannot agree. I believe that the growing popularity of the marathon is an unfortunate development for recreational running.

The word “marathon” comes from the Greek legend of Pheidippides, who is said to have run 25 miles in 490 BC from the town of Marathon to Athens to announce the defeat of the Persians in the Battle of Marathon. Pheidippides then collapsed and died, so per- haps he was delivering another message also.

The marathon was not an event in the ancient Greek games – it is a modern invention. The first modern Olympic Games was held in Athens in 1896 and the first marathon race was run at that event.

The marathon is run over an official distance of 42.195km (26 miles, 385 yards). More than 800 marathons are held worldwide annually and tens of thousands can participate in the larger events. More than 400,000 ran marathons in the US in 2008. The marathon is steadily becoming more popular. The Dublin City Marathon was founded in 1980 when 2,100 runners took part, and 12,799 runners entered for the 2009 Dublin event.

The marathon is a severe physical test and if you plan on participating you must train carefully for three to four months beforehand, following a daily running schedule. For example, if you plan to run the marathon in around four hours, your weekly training schedule will build up until you are routinely running 40-50 miles per week. Preparation schedules and advice are widely available, on dublinmarathon.ie, for example.

When you train hard your body suffers damage but it repairs itself, becoming stronger and more resistant to damage during further exertion. In this way you gradually build up your resistance until eventually the Big Day arrives. You could do significant harm to yourself if you undertook a marathon without adequate preparation.

Many studies have demonstrated the physiological, biochemical and physical effects of running a marathon. Changes in the immune system and in kidney function have been measured and the muscles, including the heart, are subjected to severe stress. A study published in the American Journal of Cardiology(Vol 88, 2001) found elevated levels of thickening factors in the blood of marathon runners 24 hours after the race. Another study publicised in the journal Circulation ( Vol 114, 2006) tested the hearts (using ultrasound) and bloods of 60 non-elite Boston marathon finishers. The results showed that, after the race, hearts in some runners had difficulty in re-filling chambers and abnormalities were noted in the way blood was pumped from the heart to the lungs. The runners also had elevated blood markers indicating heart damage.

Heart damage such as that reported in the Circulation article is not permanent and within a month after the race all runners showed relatively normal cardiac function again. However, the fact remains that during the marathon itself, and for several hours afterwards, the heart and blood enter a danger zone that increases the risk of a cardiac event, particularly in middle-aged runners with silent coronary-artery disease. Also, regular high-mileage running exerts a heavy toll on leg joints.

Aerobic exercise is very good for physical and mental health. But moderate exercise is sufficient to give you all the health benefits available from running. Increasing the levels of running beyond moderate levels does not produce any additional health benefit. To get the maximum health benefit from running, you do not need to run more than three or four four-mile sessions per week, each session run in 45-50 minutes.

The vast majority of participants in marathons are recreational runners, people who take up running as a pleasurable healthy exercise. In my opinion, the marathon is far too severe for recreational runners. Also, in my experience, a number of people who start running in order to run a marathon drop out of running once the marathon goal is achieved, thereby foregoing the ongoing health benefits that running confers.

I would encourage people to take up running, but unless you plan to become an elite athlete, build up a habit of moderate running that you can easily incorporate into a sensible lifestyle, a healthy habit that you can maintain into your old age.

William Reville is associate professor of biochemistry and public awareness of science officer at UCC – understandingscience.ucc.ie