Dr. Squat - Dr. Fred Hatfield

First of all, I wouldn't just assume muscle fiber type only by knowing ones ability to have endurance or extreme strength in a given movement. The first reason being is that I highly doubt that different people have much of a difference when comparing the ratios of type I muscle fibers to type II muscle fibers. Additionally, skill in a specific movement can really make a big difference in how one would do regardless of muscle fiber type. I do however believe that one can much more easily change their muscle fibers from type IIb to type IIa and the other way around, through proper training.

Anyways, to be more specific about your question, type II muscle fibers have the most potential for growth as opposed to type I fibers. Type I muscle fibers come into play mostly when doing long endurance events such as running. But when resistance is added, the type II fibers will come into play the most, because they are needed in order to produce enough force to perform the movement. Also realize that the muscle fiber types involved can't be determined solely on the amount of reps being performed. Tom wasn't squatting 50 lbs for 23 reps. He was squatting 500! And 500 lbs takes some serious strength just to do it once! Surely slow twitch muscle fibers are going to have to come into play, but they are not taking the brute of the movement.

My bet is that Tom's type IIa muscle fibers were really big and that he had more type IIa fibers than type IIb fibers. But possibly not though because he didn't train legs that often. He used to train legs once every 10-14 days. Type IIa muscle fibers turn to type IIb muscle fibers when you are resting. So it is possible that Tom did enough work to stimulate some serious growth in his type IIa muscle fibers and turn his type IIb muscle fibers to type IIa muscle fibers after a hard workout, and then perhaps a lot of the type IIa fibers turned into type IIb fibers over the week or so while he was resting. It's a crazy thought, but surely possible. Either way, Tom was stimulating some serious growth in all of his muscle fibers in order to gain the maximum size.

The other thing is that Tom didn't do his workouts like your typical guy. His workouts were extremely brutal. If hyperplasia actually was possible and likely, I wouldn't be surprised if he made that happen as well.

Kid, interesting topic man. Tom was definitely an inspiration to me when I was younger. He was amazing. If it werent for him I'm not sure I would have taken my fitness to what I did over the years. I probably would not have had big legs like I always have.

On the money, Todd!