I just want to interject really quick to explain a few things, as I feel many are not fulling grasping the applied science behind KM's program. I'll try to keep it simple and easy to understand.
First, some muscle cell biology.
A muscle cell (or fiber) are the longest cells in your body. They stretch the length of your muscles. In them, are little contractile mechanisms that run the length of the muscle fiber called myofibrils. Its these proteins that when excited shorten causing your muscles to contract and thus movement to take place.
Outside of the myofibril is the sarcoplasm and intrasarcoplasmic organelles. These organelles, and the sarcoplasm around them which is almost entirely water perform every other cellular function from metabolism to protein synthesis (the creating of more and thicker myofibrils).
Outside the muscle fiber lies satellite, or stem cells.
Here's the significance. Your muscles grow not by creating new cells (hyperplasia) but by increasing the girth of the individual muscle fibers themselves (hypertrophy). This process is done in two ways.
1. By increasing the size and number of myofibrils. Myofibril hypertrophy.
2. The sattelite cells "spill" their contents into the muscle fiber, resulting in more sarcoplasm and intrasarcoplasmic organelles.
Which brings us to the reasoning behind the program.
Utilizing a load of 75-85% of ones 1rm (about 5-7 reps) and a work to rest ratio of at least 3 or 4:1 (consider an average set of 5-7 reps taking about 20-40 seconds, depending on the exercise) the resulting adaptation is larger and more numerous myofibrils. This also accounts for the greater strength gains when training in such a rep range versus that of a higher one.
Utilizing a load of 65-75% of ones 1rm, or about 8-12 reps and a work to rest ratio of 1:2 (considering an average set lasting 30-45 seconds) does not allow for full recovery between sets and results in sarcoplasmic hypertrophy, as the cell tries to increase the necessary machinery in order to "keep up" with such work.
The problem with focusing on only one for a period of time then focusing on the other is that atrophy occurs in the aspect not being trained. So if you spend 6 weeks using a rep range of 5-7 and longer rest periods, you may get bigger as your myofibrils increase, but as this is happening there is no change of even atrophy in the sarcoplasmic size.
Then, as most programs go, spending the next 6 weeks (or switching it up..as they say) utilizing a higher rep range and shorter rest period your muscles will grow due to sarcoplasmic hypertrophy, but your myofibrils will either stay the same size or atrophy. Which explains why often many well trained body builders find themselves weaker when returning to the lower rep range.
So, as KM's program is set up, he increases both at once.
Other programs, for more experienced bodybuilders who are closer to their genetic limits, may have to focus on increasing one aspect while maintaining the second. I can explain how to set up such a program at a later date.
I hope this has shed some light on the issue.
Br
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