Caleb Canal posts screenshots of graphs showing his cycling, running and walking activities to Instagram, as well as photos from workouts. Sharing small victories and receiving virtual pats on the back on social networks was especially welcome when Canal first started doing training runs for a marathon in 2010 -- losing 60 pounds in the process.
"Without a social fitness-tracking website like RunKeeper, no one would usually take notice of that run," he said. "There's no gunshot start, no water stops, no cheering crowds, and no finish line, unless it's your own driveway."
Amara Poolswasdi sometimes checks encouraging messages on her phone while she's doing long-distance running, which she says keep her motivated -- "especially when things get rough."
She started running as a challenge to herself to get in shape for a 5K and, nine months later, she completed her first marathon. She tracked her running stats and posted them to her public blog as well as social media.
People using mobile apps that don't have options for messaging, like FitBit, will take screenshots of their leaderboard and share with the friends they're competing with on Twitter or over text message. In many of these cases it's for bragging rights and a bit of light smack talk.
"Support in the form of a challenge always motivates me more than a typical 'Good Job' or 'You Killed that Ride,'" said cyclist Steve Ford, who recently completed his first triathlon.
Not just about motivation
Even when they're trading insults, friends can provide valuable information on how to improve techniques and workouts. People who live in the same area can see the best biking or jogging routes suggested by other people.
Fitness tracking tools that let you connect with strangers are a good way to pair up with people who are at a similar fitness level.
"One way that people gain self-confidence is when they see other people of similar ability doing things," said Gapin. "It helps people improve adherence to exercise."
In addition to messaging and Twitter, many people on these networks are trading tips and giving each other guidance on message boards.
"Change isn't just about motivation," said Fogg. "As important is helping people learn 'how to' and increasing their ability."