Sometimes after exercise or hard work I have back pain due to which I feel pain while bending or straightening. It feel like a muscle is stretching under the back bone. Similarly if I do sit-up r jump or or lifting weights in bending I feel a lot of pain like a muscles is stretching and it makes me unable to sit-up. These problems automatically get reduces if I don't do any kind of work or exercise. Please suggest me what will I do? Or am I suffering from any disease?