NEW YORK – Two years ago, Ms Amy Gruenhut developed a near-fatal brain infection that put her in a coma for nearly two weeks. Since then, she has gone from learning how to eat, speak and walk again to running four marathons.

Ms Gruenhut had been a casual runner before the coma, but after she left the hospital, returning to the jogging paths of Central Park felt like a return to life itself.

Making progress required patience and willpower that seemed almost superhuman. But, like everyone, she sometimes struggled to get out of bed and lace up her sneakers. For those moments, she amassed a group of workout buddies to encourage her to get moving.

“I didn’t want to stand them up,” the 44-year-old said, adding: “They were making that commitment to me as well.”

Regardless of how inspired people are to achieve their health and fitness goals, many face barriers to putting in the time, reps or steps. But experts say the difference between quitting and not quitting often comes down to having a person, group, app or other outside force that nudges you to keep going.

Most accountability tricks are not universal: One person might find it motivating to share run times on the fitness app Strava; another might find it deeply stressful. The key is to shop around until you find a strategy that works for you.

Find a more committed buddy or one who needs an extra push

Making plans to exercise with a friend increases your chances of working out. But some experts say people benefit most from teaming up with one who is more enthusiastic about working out than they are.

A new study on gym motivation, soon to be published in the journal Management Science, found that participants who struggled to work out saw significant improvement when they buddied up with a regular gymgoer, said assist...