Uncovering and explaining how our digital world is changing — and changing us.

Strava, maker of a popular mobile app for cycling and other athletic endeavors, has raised $18.5 million in Series D funding and brought in a renowned venture capitalist as an advisor.

Sequoia Capital is leading the round, with partner Michael Moritz becoming an adviser to Strava. Current investors Sigma West and Madrone Capital Partners have also contributed.

Strava CEO Mark Gainey said in an interview that San Francisco-based Strava, which was founded in 2009, plans to use the funding for “growth expansion.”

“We’re now approaching the point where 75 percent of our users exist outside of the U.S.,” he said. “We’re also seeing that people are using Strava across multiple sports, so we’re exploring how to build out the service in an authentic way in all areas of sports.”

Gainey, who took over as CEO last year when co-founder and good friend Michael Horvath stepped down for personal reasons, declined to say how many users Strava has. He also did not say what percentage of users are paying customers. Around three million activities are recorded in the app each week.

Strava, which runs on iOS and Android devices, is free to download and use, with a premium option that costs $59 a year. The company actually has three revenue streams; the largest is the premium subscription service. Strava also sells gadgets and gear through the app and shares anonymized data with municipalities for mapping and urban planning purposes.

It works like many other health and fitness apps: It utilizes the GPS and sensor capabilities in the smartphone to record your workout distance and time, including lap or split times.

What’s different about the app is that it has somehow managed to attract a rabid community of cyclists who can view each other’s workouts and compete in the virtual world of Strava (especially in the San Francisco Bay Area, where the saying goes, “If it’s not on Strava, it didn’t happen”).

And it’s not just for cyclists, as Gainey pointed out. Around 30 percent of users log running activities, and 10 percent to 15 percent of users record other activities in the app, including hiking, skiing, weight training, swimming and yoga.

The funding will also go toward international expansion. Despite the fact that it’s growing overseas, “the Bay Area continues to be a bit of a bubble for us,” Gainey admitted, and most international users are from English-speaking countries.

Sequoia’s Moritz said, “We think that Strava is cleverly engaged with a sizable audience and is developing the personal sporting network in a way that’s different from many other apps.”

He added: “Also, my advice is that whoever is on Strava should never, ever try to emulate my own athletic performance. It isn’t the path to growth for any individual.”