So from what I've read, for all muscle fibers, you never gain anymore but you can cause more hypertrophy in the certain slow and fast-twitch based on your training.
Whatever you're genetically determined for fast and slow-twitch fibers remain the same. However with certain training, let's say if you train doing heavy anaerobic training with fast-twitch fibers, the fast-twitch fibers will be trained more and cause more hypertrophy in those fast-twitch fibers. You'll have the same amount of fast and slow-twitch fibers, but the fast ones will have more hypertrophy.
BTW, from what I've read humans only have type I slow-twitch and type IIa and IIx fast-twitch. IIx is white anaerobic. Type IIb is in other animals like rodents for their jaw muscles which are the strongest type of muscle fibers.
|