Close to midnight on the night before the Macau marathon last year, Matt Moroz ran frantically around his hotel block. He should have been resting; instead he was trying to reach the top of Hong Kong's running leader boards on the fitness-tracking app Strava. His late night sprint brought his month's mileage to 381.2km, winning him the December title for most kilometres run, but no prize - except bragging rights. His tale is just one of thousands like it from Strava's rapidly growing fan base, motivated by the app's engineering: users can record, share, analyse and compare workouts, making it the Facebook of fitness. Strava does what most GPS-enabled tracking apps do: maps activities and measures, among other things, distance, moving time, average speed, pace and total calories burned for 28 types of activities. But Strava stands apart in cycling and running. The app tracks speed and pace over particular "segments" - ranging from a few hundred metres to several kilometres - and ranks an individual's efforts. The fastest in each segment gains the accolade of "king [or queen)]of the mountain" (KOM/QOM) in cycling, or holding the "course record" (CR) in running. Weekly activities and mileage are tallied and are viewable, unless they are hidden, by anyone wishing to see them. Athletes are able to give each other "kudos" and comment on each other's efforts, connecting athletes around the world. If you use Strava you'll know what effect this has on your daily run or ride. Your solitary plod is thrust on to a global platform and becomes part of a collective experience with a highly competitive twist. In five years, the app has created a virtual global community of cyclists and runners, growing at a rate of 100,000 new users a week. The San Francisco-based company, founded in 2009, declines to reveal its total number of users. But at the Strava Lab labs.strava.com they present a visual dataset that's growing by more than three million activities a week; it already contains 400 billion GPS data points. It is frighteningly addictive and it's changing the way we run and ride. "I fell in love with it," says Moroz, 38, a personal trainer, who started using the app just over a year ago. "Everyone's a rock star on Strava." Moroz primarily uses the app as a motivational tool, taking advantage of segments for all-out efforts during his runs. But he has also discovered the app's unique ability to connect with a niche group of running friends around the world. "I met one of the runners on my running team, Team Joint Dynamics, through Strava. He stole my course record [on a segment] and I commented on his activity, and we struck up a conversation." Cyclist Rupert Griffiths, 44, is also drawn to Strava's competitive features, and likens "segment hunting" to a sport in itself. "Strava has helped me to set targets and accurately ensure improvements in the past three years," he says. "The app's features have helped me to identify where I was losing or gaining time so I could change my strategy for pace on any particular segment. "But it's not all about being fast. Total training time and distances are another motive. Seeing how hard you are working in comparison to others helps drive you to train more." Being able to create clubs on Strava has helped Griffiths bring together Hong Kong-based cycling team Project 852. The informal association of cyclists competes in international races and, while at home, jostle to be at the top of the club's weekly leader board of 53 cyclists. "When you click the snooze button on the alarm clock and stay in bed, you know you'll check Strava later and see you missed a great ride with your training buddies," says Griffiths. Strava's monthly challenges are another motivating feature. They consist of the greatest cumulative distance, the biggest vertical gain in a month, and the fastest time over a distance. Between Christmas and New Year, Strava joined up with London-based cycling apparel company Rapha to challenge members to ride 500km anywhere in the world to win a special badge. An embroidered patch was sent to all who successfully completed the Festive 500. Strava also has popular monthly running and cycling training challenges. During November 2014, more than 150,000 members participated - three times as many as the year before, says Strava co-founder Mark Gainey. Together with college friend Michael Horvath, Gainey founded the company with the intent of creating a "virtual locker room" where they could share workouts and keep each other motivated. "The interest in pushing oneself to achieve a goal is nothing new in sports," Gainey says. "Strava has simply expanded the opportunities for challenging oneself." More than 70 per cent of Strava's members live outside the US. "We've seen people share activities from every country in the world," he says. This year, it localised its apps and website by using Japanese, Korean and traditional Chinese characters. And the possibilities of the app are attracting high-profile athletes, and providing insights into their training regimes. In July, enthusiasts could follow cyclists on the Tour de France, including eventual third place winner Thibaut Pinot. In November, mountain runner Kilian Jornet Burgada joined Strava; next year, his speed attempt of Everest will be recorded and displayed to his followers. But the hype around Strava is not all positive. Along with the motivation comes frenzied competition. At east two cyclists in the US have been involved in accidents causing death, to themselves or pedestrians, under circumstances which suggest they were chasing a king of the mountain at the time. Pursuit of KOMs and CRs is known for arousing bizarre behaviour. "Anything goes as long as you're riding your bike," says Griffiths. "Taking advantage of tailwinds and lead-outs from other cyclists is considered acceptable. Some riders will target segments shortly after a typhoon in an effort to improve their times," he says. But a moral code does exist. Strava members frown upon those who obtain records by unfair means - known as "Stravassholes" - and entire blogs are dedicated to spotting cheats, such as those that use the speed enhancing Digital EPO.com to digitally improve their Strava performance. In 2013 there was a campaign against disgraced cyclist Lance Armstrong, who "won" 150 king of the mountains. Strava has been criticised for encouraging athletes to push too hard, increasing the risk of burnout and injury. "It has the potential to be detrimental to your long-term goals and, more importantly, your health," elite trail runner Rob Krar said in a December article published in Trailrunner . "Like other things, it's important to find a balance and to use it as a tool while being careful to not allow it to become a vice," he said. Gainey encourages members to keep things in perspective. "Not every ride or run should be a race," he says. "The addition of photos in Strava was one way we encourage our members to take time to enjoy their activity and share their experience with others." All users must abide with the "Stand With Us" code, and the company has developed features such as the flagging of hazardous segments, to aid safe riding and running. When used properly, Strava is a good form of entertainment says Moroz. "Taking a friend's course record on a segment is great amusement," he says, referring to the auto-generated email telling users their record has fallen. "The fact that you don't even have to tell them fuels the fire," he chuckles. "I love it when my course records get beaten, too. It makes us all work harder to get them back." life@scmp.com