Leg Extension : With this exercise the buttocks are worked and what is important is to extend each leg to the maximum, doing 15 seconds of repetitions with one leg and immediately doing the remaining 15 seconds with the other leg. Cross-leg push-ups: Do 15 seconds of push-ups and alternate both legs. Abs : Do the most repetitions in 15 seconds. End the session with some stretching exercises to avoid suffering any type of injury after training.