I noticed about four days ago that my calf muscles felt weak when I stood up. What could be the cause? I haven't changed any diet habits. I haven't started taking any vitamins either. It just start a few days ago when I was rocking in a rocking chair for a few minutes and when I got up, my calves felt really strange and weak for several minutes. Please help if you think this may be a symptom of something. Thank You, Karen.