I do a lot of running maybe between 50-60 miles per week, and the other day I think I might have strained my hamstring , So after that I took a easy for about a week 15min runs and swimming.That seemed to work, but now my front thigh about mid-way up feels numb when I rub over it, and during my runs, sometime it feels like a switch or like a tear in the mid thigh area, but I m still able to run as long as I don t do go fast. what should I do? what do you think this could be, and is this something serious?