In these Covid-19 times, outdoor exercise is still OK in many places so walking, biking, and running are welcome activities. However, a new European study shows it is important to avoid each other's slipstream when doing these activities. This info is the result of a study by engineers and aerodynamicists at KU Leuven in Belgium and Eindhoven University of Technology in the Netherlands. We’ve typically been told that appropriate and effective social distancing is 1 to 2 metres, but that’s really only effective when you are standing still inside or with minimal wind outside. But going for a walk, run, or bike ride you should be more careful. When someone breathes, sneezes, or coughs during a run, those particles remain in the air. The person running behind in the “slip-stream” will be running through this cloud of droplets. “If someone exhales, coughs, or sneezes while walking, running or cycling, most of the microdroplets are entrained in the wake or slipstream behind the runner or cyclist. The other person who runs or cycles just behind this leading person in the slipstream then moves through that cloud of droplets,” Bert Blocken, a professor of civil engineering at Eindhoven University of Technology and KU Leuven, told Belgian newspaper Het Laatste Nieuws.. The study’s simulations show that social distancing plays less of a role for two people who walk or run side by side in calm weather as their droplets end up behind them. If you’re using a staggered arrangement, you’re also less likely to catch saliva droplets from the person in front, at least when there is no substantial cross‐wind. The risk of contamination is greatest when people walk or run closely behind each other and therefore in each other’s slipstream. On the basis of these results, the scientists advise that for walking the distance of people moving in the same direction in 1 line should be at least 4–5 metres, for running and slow biking it should be 10 meters and for hard biking at least 20 meters. Also, when passing someone it is advised to already be in different lane at a considerable distance e.g. 20 meters for biking. Read more from the white paper here .