A woman squats with a barbell behind head in front of large windows. Squats are most effective exercise for legs and buttocks. No matter what your goals are weight loss or muscle gain. Correct technique of performing sit UPS for girls most important thing to master in gym. If you are doing this exercise correctly, your legs will get a good load and a big risk to get injured. Do not add pancakes on bar and first learn how to squat. During squats a serious burden get back muscles and press.