For those interested in the engineering behind it, there&#x27;s a few elements of this app that might be of interest.<p>1. Workout builder: there&#x27;s no stored workouts. Given a bunch of inputs: # of minutes, muscles to target, goals, the builder generates a workout for the user. The goal is to constantly get new workouts.<p>2. Workout calibrator: workout builder gives a workout that consists of exercises, sets, and reps. Workout calibrator assigns weight to all the sets, based on the user&#x27;s past performance for that exercise and other strongly correlated exercises. If it isn&#x27;t confident enough (not sufficiently high correlation coefficient for any past exercises) it leaves it blank for the user to fill in.<p>3. Set calibrator: the set calibrator is for calibrating a single set while in a workout. If it tells the user do 100lbs x 8 reps, and the user does 12 reps, it will adjust all subsequent exercises of that type to a more appropriate weight for 8 reps. There&#x27;s no ML here, it&#x27;s just a formula (8 rep weight = .6 * 12 rep weight, for example), but it works pretty well. This has the nice effect that if you don&#x27;t know how much weight you can lift for x reps, just grab any weight, do what you can, tell the app how much you did, and it&#x27;ll be accurately calibrated in 2-3 sets.