My husband and I are trying to get our 13-year-old daughter into an exercise routine, and we are in disagreement over the correct way of doing sit-ups.

Answer:

You are correct. The proper and most safe way to perform abdominal curls is with your knees bent and your feet flat on the floor.

This position reduces the amount of stress on the low back area and minimizes the involvement of muscles called the hip flexors while targeting the abdominal muscles.

There is really no benefit to performing the curls with your legs straight; in fact, I do not recommend it at all.