My son was instructed by a pro coach that there are two parts of long toss, both of which should be of equal duration - the spreading out period in which you "air it out" (long motion, high arc, crow hop at farthest point), this is the stretching out of the entire arm as well as the upper body - then the closing part in which you'd throw on a line (the strengthening part). The "air balls" go strictly against the grain of a cool teenager, but my son has had great benefits from this technique, and he throws a lot with no injuries , soreness or arm fatigue.