I am also agree with boss, Squat is really affective. I did it myself and got training on it. i can guide you how it can be. Stand with the Squat handles at mid chest, arms are tight to your sides and elbows are bent. Keep your feet approximately shoulder width apart. Abridge your abs and keep them tight as you bend the knees and slowly squat. Then try to sit back and down and perform the gesture resembling like you're sitting into an imaginary chair, in the due course keep your back straight and knees channelized in the same direction and in line with your toes. Go down until your thighs are parallel to the floor and your knees are over your ankles. Keep your body tight and push through your heels to bring yourself back to the starting position. Crunch is also affective. Thanks.