Is sit ups good exercise?

Sit ups are fine.: To tighten ab's: crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side bridge & “bicycling” exercise on back. Engage in regular aerobic exercise (i.e. running, swimming, Nordic track, bicycling, kickboxing, walking, cross country skiing, hiking, etc.). Doing more than one abdominal exercise is better. Take care.

One of many: Sit-ups serve a purpose to help strengthen your core muscle, just beware that sometimes they will put increased stress on your neck. Planks and crunches are also other good core exercises.