I m a relatively healthy 47 year old female (though I do have a bleeding disorder called VonWillebrands but mildly, not severely). I have recently started getting sore muscles and severe muscle cramps out of nowhere and am wondering what major causes of muscle cramps are. It started with sore neck muscles while biking-but not in the back of my neck where I thought it would be from holding my head up, more on the sides. Then I get really sore muscles in my legs as if I have worked out, which I really haven t. I climb stairs at work every day, and I stand most of the day (1st year of 1st grade teacher), but I also do a lot of sitting. I haven t had time to run or bike consistently like I used to. I also get severe muscle cramps now and then that are more than Charlie horses. Like my whole inner thigh will seize up, for example, and I m wondering what are major causes of needlessly sore muscles/major muscle cramps.