I absolutely love the abs, legs, and butt apps by Runtastic! Well worth the money. Now Im just waiting for one for arms so I can buy that too!
These apps start slow - with fewer repetitions of easier exercises. Then they progress with you as you get stronger, changing up the exercises and increasing the number of repetitions. It provides recovery time in between reps and gives enough time to transition from one exercise to the next. Love it. Thanks! (And please make one for arms!!!)
Misc.09 about Runtastic Leg Trainer Workouts