which lower body exercise is considered a compound lift?

Find a Comfortable Place for Your Hands Some people need to keep their hands locked behind their head in order to maintain the proper neck position ; this also results in more resistance and a more effective sit-up.25 Eki 2016

This exercise is also commonly known as the sit up.

Your hands should keep your head still and in place only . Using your hands for leverage will put some strain on your neck vertebrae and all the way along the spine. Relying on your hands will not engage your abdominal which just defeats the purpose of a sit-up.