As an app, Superhuman is not a bad choice. It offers some good exercises that help to improve different parts of your body and has been shown to increase stamina and strength fairly well. The only problem with it as a pre workout is that the workouts are short lived. A better option would be if you could create your own routines in the app so as long as they were short enough for you then this wouldnt be such a big deal but otherwise I dont recommend it for use before working out or any other intense physical activity