Here at 220 Triathlon, this author’s interviewed top aerodynamicist Bert Blocken of Eindhoven University of Technology a fair few times over the years, discovering nuggets such as: even the lead triathlete in a pack will enjoy a drafting benefit off the rider behind and that the middle cyclist in a huge peloton is saving around 90% energy compared to the leader. Both, Blocken calculated via computer modelling and in the wind-tunnel. Both picked up – and of interest to – participants and fans of endurance sport.
But a recent study by the Dutchmen grew from niche to the masses when Blocken conveyed his unpublished study to social media. The subject? Covid-19 and social distancing for cyclists and runners.
“Governmental advice around the world has enforced 1.5m to 2m distance between individuals,” Blocken tells us. “But this was from a standing position. We aimed to see if there was a safer run or bike formation to adopt during this crisis.”
So what was the protocol and what were the results? Well, Blocken and his team measured airflow around model runners and cyclists at three speeds within the confines of Eindhoven wind-tunnel: walking pace, a fast run and moderate cycling speed. “We then examined the evaporation of respiratory droplets,” Blocken says, though the results didn’t take into account the more real-world situations of headwinds, crosswinds or tailwinds.
The team then merged their data with past studies about how respiratory droplets spread during exercise for a number of conclusions, one of which was picked up by the tabloids: that you should be further back from 2m if you’re directly behind the person in front.
“In the absence of a headwind, tailwind or crosswind, when walking fast at about 4km/hr, you should be 5m back,” Blocken explains. “For running at 14.4km/hr, this distance is about 10m and about 20m when riding at 30km/hr.” But there is a simple solution – ride or jog side by side. Just don’t turn and cough.