What's the behaviour you're seeing? On my S0, I find that the Workouts app seems quite prone to crashing when it has been used recently (but maybe not within the past 48 hours or so). On launching it looks as if the app has resumed, i.e. there's no app loading spinner shown, but the app is completely unresponsive.
For me, forcing the app to quit by holding the side button until the shutdown prompt comes up, then holding down the digital crown until the app exits out seems to sort things out - though its not an ideal situation given how long the workouts app takes to load from scratch on a S0.