Squat: weight in heels. Shoulders rolled back. Chest out. Knees out. Below parallel if flexibility allows. Sit-up: All the way down, all the way up. Push-up: Chest to ground. Modify as needed: on knees, halfway down, or standing against wall. 10 minutes of these movements and you'll be cashed. No gym needed. Try this workout. 10 squats. 10 sit-ups. 10 push-ups. 9 squats. 9 psit-ups. 9 push-ups. 8 squats. 8 sit-ups. 8 push-ups. 7 6 ....etc.