I work out 2hr daily, recently benn having muscle pain, people had told me that I need a supplement., which vitamin will help.?

Muscle pain. Pain is the body's way of telling us not to do something . Try hydration but overuse is a possibility too. Sometimes backing off is the right thing to do. I had the same 'problem' with my son - a very high level swimmer (olympic trial cut ) he always thought more was better. Sometimes it is not.