Dr. Andy Galpin

To give you a little bit of concept of how big that is, number one, you can see that with the naked eye.

I could pull up in my laboratory a pair of tweezers, a single muscle fiber from a human.

I could hold it up right now and on this camera, you would absolutely be able to see that both on camera as well as with your naked eye if you were within even five to 10 feet of me.

In terms of cross-sectional area, you're looking at something like 4,000 to 5,000 micrometers squared, which a little bit of context there.

One time, actually, I had a long-established power lifter as well as anabolic steroid user in my lab, and we biopsied this individual, and his muscle fibers were closer to 9,000 micrometers.

And the closest equivalent we found there was actually a rhinoceros.

So muscle fibers are not only large in terms of biology, but the ability to gain size is extraordinary.

As again, I said earlier, one of the things that makes skeletal muscle in humans especially unique is the ability to respond and adapt based on stimuli.

In fact, it seems to be quite unending.

Now we'll come back and talk about muscle fibers size and how to develop it a little bit later.

But getting back to this idea of fiber number, as I mentioned, it's thought to be fairly fixed once you reach adulthood.

However, it is extremely clear that this number will go down with aging.

unless you do something proactively to prevent that.

It's actually also very clear that this number can increase with anabolic steroid use.

Now, this concept of growing new muscle fibers is called hyperplasia and something that has been hotly contested in the exercise physiology world for many, many decades.

Now, I will give you a little bit of a behind the scenes here.

I personally am always been a big believer in hyperplasia happening.

I won't say the science is strongly in my support, but it's been one of the passion projects that I'm not going to give up on.

Now, what I'm really talking about here is there's no question whatsoever that new cells can grow.

That's not really the debate.