It’s only a matter of time before a runner breaks the two-hour barrier for a marathon. But it will take the perfect blend of athlete, coaching, course, conditions and science.

Written by John Brewer.

When Sir Roger Bannister first recorded a time of under four minutes for one mile, one of the most iconic barriers in the sport of running was broken. However, there is one further barrier that remains intact, and it is one that has recently received a significant amount of publicity since a well-known shoe brand has launched a campaign to see it broken – it is, of course, the sub two-hour marathon, which when (not if) it occurs, will see one of the most impressive ever feats of human endurance.

I say when, rather than if, because in my view, and having studied the science behind the performance that will be required, I am certain that one day it will happen. It means shaving just under three minutes off the current world record, which equates to a performance improvement of 2.4%.

That is by no means a small amount, and it will take the perfect blend of athlete, coaching, course, conditions and science to make it happen. It is also likely that this breakthrough will happen in stages, rather than in one single chunk.

The athlete will need to have the right physiological characteristics to cope with the demands of sustaining the energy required to run a speed fractionally faster than 13.1 miles per hour for two hours. We know that the capacity to run at this speed for a prolonged period of time currently exists – after all the world half marathon record is already under one hour. But that sort of pace will see significant increases in heart rate, oxygen uptake, lactic acid and core temperature, and it is the ability to tolerate these increases for two hours, rather than one hour, that is critical.

We all require oxygen to support energy production, and this requirement increases linearly with running speed, until maximum oxygen uptake capacity is reached. As long ago as 1988, I published a paper in the British Journal of Sports Medicine which showed that on average runners need about 5 millilitres of oxygen per kilogram of their body weight, for each mile per hour of running speed.

So, to sustain 13.1 miles per hour the body needs an oxygen supply of around 66 millilitres per kilogram per minute (although runners who are more efficient will require slightly less). That now somewhat aged paper also found that elite marathon runners can sustain around 80% of their maximum capacity when running 26.2 miles, so a constant uptake of 66 would require a maximum value in the mid-1980s. Maximum values of this nature are not unknown in elite runners – we have seen them in our sports science lab at St Mary’s University, and similar values have been recorded elsewhere.

So, we know that we are in the realms of what is feasible, not impossible. Of course, the runner who breaks the two-hour barrier will need to be in perfect physical condition at the time of the race, and will have to have been coached to peak at exactly the right time, and followed a nutritional strategy that sees them with the right levels of fuel and hydration. Great coaching will be essential if they are to produce the perfect physical and mental performance at the right time. The course will need to be ideal – as someone who has run the occasional marathon, I know how much even the slightest of uphill slopes can take out of your legs, especially towards the end of the race, and how easy it is to lose running rhythm if there are too many twists and turns. It will probably require pacemakers too, ensuring that the correct speed is established from the start, but of course finding runners who can stay with the potential new world record holder for anything beyond the mid-stages of the race will be difficult, so that inevitably the final few miles are likely to be a tough struggle against the clock. Mental resilience and determination will be an additional essential characteristic for a sub two-hour runner.

A further ingredient in the “perfect blend” are the weather conditions on the day – too hot, and dehydration and a rise in core temperature will place additional demands on the body that will add seconds or even minutes on to the finish time. Too cold, wet or breezy, and runners will find it hard to perform efficiently, and lose time fighting against resistance from the wind.

Advances in science can also help to underpin marginal improvements in performance. For example, footwear that helps runners to become more economical and use less energy, clothing that aids heat loss and blood flow or nutritional and hydration strategies that can optimise energy stores and hydration will all help to make the small differences that combine to enhance performance by critical small percentage points.

In reality, how does a sub two-hour marathon compare with the current world record set by Dennis Kimetto in Berlin in 2014 of 2 hours 2 minutes and 57 seconds? Kimetto averaged a phenomenal 4 minutes and 42 seconds per mile, at an average speed of 12.75mph. Breaking two hours will mean running each mile seven seconds faster than Kimetto, which would, in reality, mean pulling away from him by 50 metres per mile, meaning that a sub two-hour runner would have to be a staggering 1.3km ahead of the current world record pace when crossing the finishing line. At the elite level, this type of margin is huge, and is more likely to happen in years and decades, rather than in the more immediate future.

That’s not to say that it could not happen sooner, but it would take a really exceptional talent combining with the right conditions and course on the right day to make it happen. Closer examination of the progression of the world record shows that it has taken since 1988, or 28 years, for a 3% improvement in the marathon world record to occur, and over 20 years for the previous 3% improvement to take place. So, if anything, the evidence suggests that a plateau in the rate of progression is starting to occur, and it would be unprecedented for such a large change in the world record to occur in a period of time that is considerably less.

I think it is only a matter of time before we see the two-hour barrier broken for a marathon, but it will take an exceptional talent and exceptional circumstances for it to happen. While less than three minutes may seem like a relatively small amount of time over such a long distance, the reality is this is a huge margin in terms of elite performance, and it may be many years before we see a marathon finishing time beginning with “1”.