The app uses global-positioning system (GPS) technology to record exercise, allowing users to compare performances.
Meanwhile, fitness app Freeletics, which has more than 90,000 UK users, saw a 50% increase in use between March and June, during the first lockdown.
"Covid-19 has presented many people with the unique opportunity to exercise more, because, practically, people have fewer reasons not to," Dr Charlotte Hilton, of the British Psychological society, said.
"If nothing else, exercise outdoors provides us with some welcome relief from spending so much time indoors during lockdown.
"However, because of the social restrictions that Covid-19 brings, more people may be turning to online exercise communities and apps to enhance their connectedness to other like-minded people who enjoy exercise."
Strava saw a rise in the total amount of activity logged on the app, with running and cycling proving most popular.
Those already using the app increased their workouts by 13%.
A record number of runners completed its May 5km (three-mile) challenge.