First and foremost, some things work for some guys that don't for others. I pitched in college and now coach high school and in my opinion velocity comes from 75% genetics, 15% mechanics, 10% throwing and strength training. Basically the reason someone can throw hard is mostly because they just naturally can, obviously that can be improved upon by improving mechanics and a good throwing and strength training program. I would guess Mark really didn't buy into the 30, 60, 120 program. This sounds similar to the one I was taught in college, which I didn't like. Now that he's able to do something he's more comfortable and familiar with he's being more productive with it. I've always felt that the 30, 60, 120 program was good for developing control but to build arm strength you really need to lengthen it out and train yourself to use your whole body to throw with explosiveness but still maintain proper mechanics. Throwing 300 feet for a professional pitcher should not be a big deal. Throwing a ball on a line at 300 feet is equal to about 90 MPH which Mark easily exceeds.