Let’s use a simple example of a fighter with 60% type 1, 40% type 2.
When we train with a slow speed we stimulate the Type 1’s to grow and be slow. Effectively making them even slower!
But, when we train fast we stimulate the Type 2’s to get bigger and faster!
Now the ratios (remember that 60/40 example above) of fibres has been shown to remain the same across time. Thats the way you’re built.
However, the cross-sectional area of each type will change and grow depending on the training stimulus, effectively taking up more space in the muscle.
So, you will still have 60% of those type 1 fibre types, but when training with velocity they now take up only 40% of the room!
Guess what, that leaves the fast ones, still being 40% in numbers, now taking up 60% of space in the room!
With VBT type 2’s are now a more dominant fibre in the muscle unit.
That is selective hypertrophy.
With the correct stimulus, we can select the specific fibre type we want to train and build within the athlete!