Originally posted by Bryan Haycock to the HST forums
Here's my opinion for what its worth.
Mechanical tension on the protein structures of the muscle cells is the primary stimulus for hypertrophy. This tension can elicit anabolic processes with or without damaged to the cell membrane. However, some damage to the cell membrane seems to be critical for the action of autocrine and paracrine growth factors (FGF, IGF-1, etc). Without the activity of these growth factors there will be no increase in myonuclei, and thus no significant increase the the volume and/or number of the cells.
Some improvements in muscle cell function do occur even if the number of myonuclei remains the same. These won't lead to significant hypertrophy though. These improvements in muscle cell functional capacity involve ERK1/2. This is the pathway activated most when you get an intense burn and/or train to failure.
Muscle "activity" such as the typical repetition, and the metabolic byproducts and change in the internal millieu of the cell also "contribute" to hypertrophy, but only indirectly. Reps, and fatigue activate signaling proteins and transcription factors that increase protein synthesis. This increase in protein synthesis allows an increase in crucial enzymes, receptors (yes even androgen receptors), membrane and structural proteins. Remember that protein breakdown is also accelerated so the net effect is most often merely a maintenance of muscle protein levels. This is what goes on after each workout when plateauing after years of training.
Keep in mind, that without the activity of IGF-1 and FGF outside of the cell, satellite cells will not contribute significantly to hypertrophy. The process is dependant on microtrauma at some degree. Review the material on mechanotransduction for more info.
Studies have shown too much microtrauma is a bad thing. The rapid infiltration of immune factors (the primary cause of DOMS) actually causes significant breakdown of muscle proteins and the death of some cells.
Now, the ability of mechanical tension to cause microtrauma to the cell membrane is dependant on the condition of the extracellular matrix. If it is robust as a result of chronic strain, is will take an unaccustomed load to induce any trauma. Your ability to apply this load is dependant on your voluntary strength. Your body is able to protect your muscle cells from microtrauma even when using max loads. It isn't always able to protect tendons.
HST incorporates ever increasing loads in order to stay ahead of the adaptive curve. This curve is set by the tissues level of conditioning at the time the load is applied. This is as much an art as a science. Because we can't do a biopsy of the muscles everytime we train, we ahve to guess how much, how hard, and how often, based on the avialable research an the "feeling" of the tissue at the time.
Once you have maxed out your voluntary strength levels, growth will stop. It may take several weeks for it to stall. Once this happens, HST incorporates Strategic Deconditioning in order to lower the level of conditioning of the muscle tissue. This is necessary in order to use "submax" weights. Why use submax weights? Because using max weights eventually stops working, and simply increases the risk of injury.
Is the purpose of SD to cure overtraining? No. Research has shown a week is not long enough to reverse the symptoms of overtraining. If you have been properly managing your training volume, you wont be overtrained anyway. If you are, you should adjust your training levels. [Note] Overtraining is not necessary for hypertrophy. Methods such as "over reaching" are used to increase performance, not hypertrophy.
Are the 15s of HST designed to stimulate hypertrophy? No. The 15s are designed to condition your tendons for the upcoming heavy loads.
Is there something magical about using 5-10 pound weight increments each workout? No. The idea is that the weight must steadily increase over time, or no further growth will occur. Go ahead and use the same weight twice, its no big deal. If your starting weights are too small, use fewer increments and start with more weight.
Is training every 48hours magical? No. But its pretty close! At times I have found that adding an extra day of rest during the 3rd & 4th weeks of 5s/negatives helps me feel better while I'm dieting, or extra stressed out from life issues.
Is knowing and understanding the science of muscle cell physiology necessary to perfect Hypertrophy-Specific Training? Yes.
Is understanding the science necessary to get the benefits from HST? No. But you will have a harder time making "on the fly" decisions about adjustments to your training.
Will people still ask questions about this stuff after they claim to have read the material already written? Yes. But that's not a bad thing. It gives people a chance to help eachother and have a good time talking about stuff they love to do.
Finally, please remember my motives for sharing HST over the last few years. I want to help people who want to grow. I am a bodybuilder myself. I am always trying to add muscle. The more the better. Because of unique circumstances in my life, I have collected a great deal of information about how muscles grow in response to training, food, and drugs. It has helped me tremendously. And, you reap what you sow, so, I thought I would sow and let the universe workout the rest.
Sorry for the spelling errors.