Ultra-marathons: beyond the runner’s high

Ultra-marathons: beyond the runner’s high
Science of Life

Running is fast becoming the most popular form of exercise – it is estimated that two million people run in Britain and 10 million people in the USA. The aerobic (heart and lung) exercise provided by running is undoubtedly good for your health. However, intense and arduous forms of running, such as marathons and ultra-marathons, are becoming very popular. In my opinion, this trend towards intense running is not conducive to maintaining the widespread popularity of running. Various aspects of popular running are reviewed by Christian Jarrett and Ella Rhodes in The Psychologist, May 2017.

There is voluminous evidence that running is good for both physical health – improving circulation and cardiovascular function, lowering risk of contracting many diseases, lowering body fat, cholesterol, etc. – and mental health – improves mood, quality of sleep, self-esteem and handling negative emotions.

Moderate levels

The good news is that these health benefits can all be realised through moderate levels of running – say running 5km in about 35 minutes, three/four times a week. Newcomers to running have to gradually build up to this level. Running longer and faster than this will make you athletically fitter for competition but will not add further health benefits.

Moderate running greatly assists one in coping with everyday stress. I am a moderate runner and often had the following experience. On my way to the running track my head is swimming with details of some argument I am having with a colleague, but after running I am often hard pressed to remember what I was fussing about before my run.

Running looks like hard work but it is relatively easy in practice because the rewards greatly outweigh the effort. First of all there is the ‘runners’ high’, a feeling of mild euphoria that I find kicks in after running for about 1km. This takes your mind off the hard work your legs and lungs are doing and improves your humour, making you chatty if you are running with companions. For most people, running with companions is easier and more pleasant than running alone. Secondly there is the feeling of physical and mental well-being you have between running sessions. These two effects draw you back to running time after time, making it easy to establish a habit of moderate running.

It is unclear what causes runners’ high. The conventional explanation is that running causes the brain to release endorphins, a class of opium-like chemicals. However, this hypothesis is now in doubt – other chemicals are also involved and increased body temperature seems to contribute to the effect.

I am not a fan of intense running (marathons and beyond) as a popular pastime. Too many people take up running with the goal of running a marathon. Preparation for the marathon calls for intense training and takes up most of your free time. Then, after your maiden marathon, if you plan to continue to run at this level, you must also continue the time consuming training. Many people cannot commit to this level of training and drop out of running altogether. In my opinion it would be much better if most people entered running with the goal of becoming moderate runners. This consumes only a modest fraction of your free time and can be easily maintained as a lifetime habit.

Some people take up running to lose weight. Unfortunately it is very hard to lose weight through exercise. The only efficient way is to reduce your calorie intake. Basically, you run for good health and you control your weight by regulating your diet.

The only downside I see to moderate running is that some people develop ‘wear and tear’ in knee or hip joints after years of running. This risk can be reduced by wearing good running shoes and running on softer ground e.g. grass.

I define the entry-level to intense running as the half marathon, progressing on to the marathon and then to ultra-marathons. The traditional marathon is 42.195km long (26.22 miles) and any distance longer than this is an ultra-marathon. The marathon race is inspired by the story of Pheidippides who ran about 25 miles from the Greek city of Marathon to Athens in 490BC to announce the defeat of the Persians in the Battle of Marathon. On arrival, he collapsed and died after gasping out: “We were victorious.” The fact that he died is usually omitted from the story!


Most people assume the marathon was the highlight of the ancient Olympics, but not so. No race longer than three miles figured in these games. The marathon is a modern event introduced to launch the modern Olympics in 1896. However, the Greeks did use runners to carry messages from city to city and these runners would run all day.

The most common ultra-marathon events are 50km and 100km long and 50 miles and 100 miles long. Probably the most extreme ultra-marathon event is the annual Marathon Des Sables (Marathon of the Sands), a 251km (156 miles) trek through the Sahara Desert in Southern Morocco. This race is run in six stages over seven days, with temperatures often soaring to 50°C. Runners carry their own food, water and equipment on their backs. Three runners have died to-date participating in this event.


Some people who take up running discover that they have a marked capacity for running. In due course, these runners can cautiously progress from moderate running to half-marathons and even to marathons, while keeping an eye out to ensure that running doesn’t rob a disproportionate amount of free time from other important things such as family, friends and other pursuits.

But I cannot enthuse at all about ultra-marathons. These events go beyond the endurance design-level of the human body and it is not uncommon for ultra-runners to experience hallucinations while running. Ultra-marathon running is for the very few indeed.

In summary, running is a natural, pleasurable and healthy form of popular exercise, but it pays to be sensible about it.

William Reville is an Emeritus Professor of Biochemistry at UCC.