The explosion of fitness apps in recent years hasn't necessarily led to a fitter nation.

The fitness industry is trying to change that by redesigning apps. The idea is to encourage users to engage in healthy activities that they already enjoy, rather than to push them to engage in exercise that they feel like they're being guilted into.

There are already examples of apps that have succeeded at getting people active, perhaps unwillingly. The most prominent example is Pokemon Go!, which prodded millions of smartphone users to venture around their communities in search of Pokemon to catch. In addition to the fitness benefit, some people suffering from anxiety-related disorders said that the game had helped them conquer the psychological barriers that prevented them from leaving their homes and interacting with the outside world.