17 Game-Changing Health Start-ups

GAIN Fitness
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GAIN Fitness

GAIN is an iPhone and Web app that lets you quickly create custom, pro-quality workouts to do at home or the gym. The app instructs you on how to perform each exercise and how many sets and reps to do for each, depending on your goals and fitness level. The app also quantifies your performance using an in-built tracking and analytics system. The app works seamlessly with your phone's music player, and has audio coaching that will fade in and out with music to allow for optional instruction. Within the past year, the Web version has received more than 800,000 unique visitors and the iOS app has conducted more than a million mobile sessions with the majority of users accessing custom GAIN workouts using an iPhone or iPod Touch.—Christina DesMarais