Yes, sit-ups will help. Twist while you do them. The key is to do them often and lots of reps. Take the time...it pays off. It is important to have a strong core.

I was slacking off on sit-ups for the past month because I was focasing on cyling and my back started to feel sore. I realized I was neglecting my upper body. So, I started back to the gym for some boxing and weights. I feel better already.