I am 44yrs. Old and 5'10", 240 lbs. I am physically very strong. However, I have been walking 1-2 hrs. a day, 3-6 miles, and my upper front part of my ankles or lower shins just burn. I have tried stretching beforehand by pulling my toes backward under myself, and this feels better but the muscle pain still persists. Is this normal? And what am I doing wrong? I have tried Sports Creams, and this does help, but why is this happening to me?