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How to do abdominal crunches with angled heels
Lie down facing the ceiling with your knees bent and your shoulders, hips, and feet aligned.
Flatten your back and clench your abs, clasping your hands together behind your head.
Raise your toes up so that your heels press into the ground.
This should work your upper thigh muscles; if you do not feel the effort there, try pressing a little harder. Bring your head and shoulders up towards your hips in a typical crunch motion.