What should I be focusing on when doing a situp?
The primary thing you should focus on is contracting (tightening) your abdominals as you bring your chest to your knees.
Are there ways to reduce strain on muscle groups that should not be getting strained?
I never do the traditional sit-up anymore because it puts so much strain on other areas, and there are safer and more effective exercises to focus on. That said, here are some ways you can reduce the strain on your body during a sit-up:
- Support your head with your neck. Have your hands cupped behind your head during the exercise, gently supporting your neck so it is in alignment with the spine.
- Don't lift with your head. There is a tendency in some to use their hands to lift their head up through the movement, making the head the primary driver. Avoid this and use the form described above.
- Don't swing. It is very tempting to use body momentum when exercising to squeeze out a last rep or two, but avoid this because at best you aren't working out the muscle and at worst you are straining other muscle groups. Keep the feet firmly planted, and use steady, controlled movements.