skinny chicken arms

today6212

hey everyone, im having a problem with my arms and back. My lower body is really toned through jogging, walking and mountain biking. my arms and back are so weak and skinny! i lift 8 lb weights 3-4 days a week, i do as many push-ups(3 is my sad high lol) and i can half do a single pull up. Im 5'0 i threw my scale out so i dont know my exact weight, but id estimate 115-120lbs. My thighs are 18in, my waist is 26in but my chicken arms are only 8.5 inches. I go over my protein everyday. I dont really like carbs tho, i maybe get 50% what im supposed to everyday. Could this be the problem, or am I destined to have chicken arms forever?