France's sports ministry said Thursday that joggers and cyclists will have to stay at least 10 metres (33 feet) from one another once stay-at-home orders are lifted on May 11.
The measures are designed to prevent a surge of new coronavirus cases.
Running has become a popular way to get a break from the nationwide lockdown in place since mid-March, since short exercise jaunts close to home are among the handful of accepted reasons for being outside.
But officials have been alarmed by scenes of hundreds of runners crowding sunny sidewalks and promenades in recent weeks, leading Paris authorities to even ban day-time running.
French guidelines urge people to maintain at least one metre of social distancing in public, but a preliminary study that went viral early in April suggested this is not enough for runners or cyclists.
The study suggested that air currents generated by fast-moving bodies could spread virus particles projected by infected athletes much further than a person standing still.
The results have not been published in a peer-reviewed journal.
Nevertheless, the sports ministry said it wanted "a minimum distance of 10 metres between two people who are cycling or jogging."
It did not clarify how the measure would be enforced in Paris and other crowded cities, where runners often pass each other closely on sidewalks and footpaths.
For yoga, tennis and other activities, the ministry advised making sure that each participant had four square metres (43 square feet) of personal space.
In any case, no more than 10 people will be allowed to gather for any group activity, and changing rooms will remain off-limits.
Team sports such as football will also remain prohibited, it said.
The ministry reiterated that no professional sports matches will be held before August, even in empty stadiums, and France's football and rugby leagues declared their seasons on Thursday.
The new rules came as France this week unveiled 20 million euros ($21.8 million) in aid to encourage the use of bicycles post-lockdown, which could reduce crowding on public transport and also avoid a surge in car use by people afraid of contagion.
The funds will include a 50-euro subsidy for tune-ups of the estimated 30 million used bikes around the country, the environmental ministry said late Wednesday.