There is NO EVIDENCE to suggest that you can switch fiber types from type I to type II.[/quote]
But it IS theorised isn’t it, and you must agree that a lack of evidence does not prove anything.[quote]
There is very good evidence to suggest that in SOME muscles, for example the paraspinals, the type I fibers can be bigger than type II.[/quote]
Really? that is very interesting - especially as it is the absolute opposite to popular belief.[quote]
WITH TRAINING, ANY FORM OF TRAINING, the predominant phenotypical shift is to decrease the relative percentage of type IIb fibers, and increase the relative number of type IIa fibers.[/quote]
Is this because the latter is generally more efficient? If not, why?[quote]
With strength training, this occurs with concurrent HYPERTROPHY of the muscle fiber cross sectional area (all fiber types).
Although NOT PROVEN in humans, it does seem we may have the potential to increase the total number of muscle fibers, which is HYPERPLASIA.[/quote]
Again, a lack of evidence is not the same as evidence disproving the occurance (i am not so much stating this for your benefit as you clearly have opinions of your own on the mater, more for some of those reading).[quote]
Most of the hypertrophy measured is directly due to increased fiber size, not sarcoplasmic hypertrophy.[/quote]
Measured when? In rodent soleus cross sections? Not being picky, but where (what measurements) do you mean?
Also - for my clarification only, do you mean sarcomere hypertrophy? :)[quote]
If you do extensive training in both an endurance and strength context, while you can increase the relative proportion of type IIa fibers, the impairment in protein synthesis, the so-called INTERFERENCE PHENOMENON, will mean that gains in cross sectional area will be impaired.
STEROIDS tend to increase an individuals capacity to hypertrophy their type I muscle fibers to a greater extent than individuals not using AAS (yes, helps type II hypertrophy as well, but the big area of influence seems to be on hypertrophy of type I fibers).[/quote]
What would be the reason for this?[quote]
Type II muscle fibers get bigger when they are exposed to a heavier load, type I fibers tend to hypertrophy regardless of load intensity.[/quote]
Which is direct relation to the size principle is assume?[quote]
Fiber type composition in each muscle is very individual, and, for training purposes, IS OVERRATED.[/quote]
I don’t agree personally, i find having a knowledge of such things assists my training greatly, as opposed to stabbing around in the dark.[quote]
What is more relevant is the inherent architecture, and the potential for change.
Only continue reading if you don’t mind thinking a bit about muscle structure/function. If not, STOP NOW.
A muscle with a penniform arrangement, where the fibers are aligned at an angle to the tendon/line of pull, have greater force producing capability at LOW VELOCITY. As you increase movement velocity, they lose their effectiveness. This would suggest that training a muscle group, such as the quads, at high velocity, is a waste of time. Pennated muscles also have greater potential to increase their cross sectional area as you can essentially pack more in, as well as a greater ability to change the angle of pennation to pack even more in.
A fusiform muscle is where the fibers are aligned parallel to the line of pull. They are generally smaller, as you can’t pack as much in with the way the space is utilized. These muscles tend to be more efficient at maintaining a maximal level of force generation across a range of movement velocities. This would suggest that a muscle group, such as the hamstrings or biceps for example, will probably respond quite nicely across a range of training velocities as it can generate similar high forces regardless of speed.[/quote]