As we approach some key road races, I thought it would be interesting to discuss a recent study to come out about the effect of drafting behind another runner. We have seen anecdotally through the Breaking Two project and the Ineos 1:59 Challenge the value that is placed on protecting the runner (in both cases, Eliud Kipchoge) but how does this filter down towards the back of the pack?
Earlier research suggested that running into still air at an elite level exerts a drag of 8 Newtons and drafting behind someone could drop that drag to 4 Newtons. If you imagine that a medium sized apple weighs 1 Newton, it is like towing a small bag of apples behind you during the course of the marathon.
A new study has provided a calculation of the additional energy cost of towing that small bag of unhelpful race nutrition. Across three testing speeds, the researchers found that energy consumption increased by about 6% for every increase of 1% of body weight in the force pulling them backwards.
For Eliud Kipchoge who weighs 52kg and potentially runs 2:00 pace with no pacers the drag force is 1.39% of his body weight which means he is burning 7.8% more energy than he would if he weren’t to have the perfect rotation of pacers. Over the course of the marathon distance, that pacing saves him 6:28. Realistically, for him to have that large a saving, he would need to be running in a vacuum. However, as a real world example, if Kipchoge was to have three pacers, that formation would block 57.3% of the drag force which would translate into a 3:42 saving.
Interestingly, and not surprisingly, the most effective configuration is a seven person inverted arrow (think the Ineos 1:59 Challenge formation). That configuration blocks 85% of drag force corresponding to a massive saving of 5:29.
(Photo from ABC News - https://www.abc.net.au/news/2019-10-12/eliud-kipchoge-runs-marathon-in-under-two-hours/11597186)
Now, how about the rest of us? Even in an ‘imperfect’ drafting situation, the benefit is worthwhile. According to the study, a typical 65kg runner drafting behind the simplest three-person formation would save 3:08 over the course of a 3:00 marathon, 2:59 over the course of a 4:00 marathon and 3:00 over a 5:00 marathon.
The take away from this is, utilise pacers when they are there, find yourself a group, and do no work. You won’t make any friends with that advice but you may just out sprint your competition.