It's an unusual combination, but my 14 year old son is a pitcher and also a linebacker in football. He has a passion for both, and wants to increase bulk in order to start on the 9th grade football team next year. He's 5'8", 135lbs and is doing strength and conditioning 2x 1 hour every week that includes sprinting, lateral and backward movement, ladder drills, hops, etc. along with ab and leg work, pushups, and stretching.
He's also working out with his pitching coach 3 times per week, using medballs, weighted baseballs, tube work, and running.
My question is, what types of excercises would help him gain size without compromising his ability to throw the baseball?
Thanks in advance.