On the 12th of October 2019, a mark that was once seen as impossible was broken by Eliud Kipchoge. Crossing the finish line in 1:59:40 hours, minutes and seconds, Kipchoge became the first human ever to complete a marathon in under 2 hours. He was helped along the way by pacemakers and a track perfectly suited to his running style, in addition to shoes specially designed for efficiency. Even with all this help, his feat was, and still is, truly extraordinarily. 

Over the last 30 years, the fastest marathon time for men and women has slowly been improving. The improved technology in running shoes as well as clothing, greater support teams and nutrition has helped athletes run ever faster. But how fast can we actually go? And just like 20 years ago, when we thought 2 hours was unbreakable, will we, 50 years from now, see 1:30:00 as the new barrier to break, or will it be even lower?

There are four main factors to consider. The chief limiting factor behind our marathon running speed is our VO2. VO2 represents how much blood the heart can pump and how much oxygen gets taken from the blood stream by our muscles. The higher our VO2, the less oxygen and energy we need to run at a certain pace. This means that the lower our oxygen consumption, the better, as we then can be far more efficient and use the oxygen elsewhere/later on. Furthermore, the higher our VO2, the less lactic acid and anaerobic respiration we undergo, which helps us feel less pain and lets our muscles function better. Secondly, our maximum oxygen intake also matters significantly. This affects how much oxygen we get to our muscles, which allow us to remove lactic acid that is produced in anaerobic respiration. Our maximum intake is therefore vital, as it helps to limit how much lactic acid is produced. Third, running economy. Our running economy is the rate at which we use energy when running, which determines how much longer we can run for based on whether we still have enough energy. Finally, our lactate threshold. Our lactate threshold is the amount of effort our body can maintain before it starts to release lactic acid, and how much lactic acid we can keep in our body before we have to stop. This means that over time, as we build up lactic acid during a marathon, that activates our anaerobic system and after a while, we can no longer keep running.

We can obviously improve on all these fronts. We can exercise at our lactate threshold to improve efficiency. We can train at lower heart rates to improve VO2. But even the fittest athletes of all time are fundamentally limited by being humans and by their respective metabolisms. When a group of amateur sprinters ran the marathon last year in 200m sprint sections, they managed a marathon in 1:30:00. In Michael Joyner’s 1991 paper, he calculated the fastest time that humans can ever run the marathon will be 1:57:58.  

Nevertheless, given that for endurance sport, we are never truly at our body’s physical maximum, it can also be argued that there is no theoretical maximum. This relies on the fact that even as lactate builds up, it is possible for us to continue to deal with the lactic acid, to push through the burning sensation. This places extra emphasis on our mental resilience and pain tolerance, rather than on our purely physical capacity. Even with ridiculously high levels of lactic acid, it is theoretically still possible for you to continue running and to complete the marathon, which shows why perhaps the mental aspect of endurance sport, and of the marathon in particular, is more important even than the physical.

Ultimately, when it comes to it, we simply do not know what the maximum capacity of a human being is when running. Perhaps Joyner was right all along with his 1 hour 57 minutes and 58 second prediction, or perhaps the human body can, with mental fortitude, just carve out that single extra second, to hit 1:57:57, or even lower yet. As ever, who knows what the future will hold.

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