What I struggle with is understanding the actual physiological effects of rep ranges in all this, and whether this needs purposeful addressing in a cycle (which admittedly, HST still does, albeit not as a primary focus as such). Some programs do focus solely on metabolic stress for a bit (to mimic occlusion effect), then work on mechanical tension stuff.
Yet others will do all (DUP) within the span of a week, and work on them all at the same time. (Not to mention muscle damage/loaded stretch stuff as well, Schoenfeld discussed this also as a hypertrophy mechanism...).
Just wondering where this fits in. To focus on these (via dedicated 'days' or cycles); or not, and keep progression of load as a priority...
Short answer: All of the known mechanisms by which lifting induces muscle growth are present in a routine that has both high and low reps/relative loads regularly taken to near muscle failure. There is not yet evidence to show that simple progression schemes are inferior to DUP schedules, and vice versa. This is because all the mechanisms have tremendous overlap.
Long and somewhat rambling answer:
Rep Ranges
Unlike strength, which is measured/determined in terms of reps successfully completed with a given load, the effectiveness of a set to stimulate muscle growth cannot be determined solely on the numbers of reps successfully completed with a given load.
A contracting muscle experiences a sudden and dramatic shift in its internal chemical (and genetic) environment. It also experiences significant distortion/stretch of its cytoskeleton (i.e. the protein structures that give the cell its shape and provide rigidity for contractile proteins to anchor themselves.) This shifting and distortion is a dynamic process, meaning that both are temporary and constantly changing while the muscle is performing reps. Subsequent anabolic signaling within the cell is in response to these sudden and dramatic changes.
Time under tension
This important principle is referred to in different ways, but it simply implies that there is a threshold for time under tension that must be reached for anabolic signaling to be meaningful. With respect to reps, the more reps you perform the longer the time under tension. This can mean the time of one set or the time added together from multiple sets. One important thing to know about time under tension is that there is not a set minimum amount of time that must be reached. In general, the lower the load, the longer the time required to stimulate growth. Likewise, the heavier the load the less time is required. This relationship has limits however, for example, doing singles with your 1RM has not been shown to be effective for stimulating growth. Likewise too little weight will not stimulate growth no matter how many reps you perform. So, goal is to lift enough weight for enough reps at any given point in your cycle.
For a working muscle, a set of reps with a relatively low load, and relatively few reps, will cause minimal/negligible change to the internal environment and cytoskeleton. As a result, the anabolic signaling will also be minimal/negligible. Conversely, a set of reps with a relatively heavy load, and relatively high reps, will cause maximal change to the internal environment and cytoskeleton. As a result, the anabolic signaling will also be maximal.
If that were the end of the story, we would all be using the same routine. A routine called “go big or go home”, by others it’s called, “shut up and lift”. You get the picture. All you would have to do is go to the gym, lift as heavy and as long as you can, and repeat. But it’s not the end of the story. The story includes one very important caveat; over time the same weight lifted for the same number of reps does not cause the same amount of change and anabolic response in the muscle tissue!
A moving target
The muscle will respond differently to the same combination of weight and reps over time. This change in how the muscle responds is caused by the following factors; 1) the “resulting” condition (due to previous bout) of the muscle at the time load was applied, 2) how much time has passed since the previous time the muscle was trained, 3) the ability of the tissue to respond anabolically to the current bout (due to genetics, age, nutrition, hormones, rest, stress, etc), and 4) the extent of adaptation (both metabolic and structural) since the previous bout (i.e. RBE). These variables or “unknowns” can be described in other ways, but you get the point. These variables are like electrons, you can’t know exactly where they are at any given time, but you can have a good idea of where they should be.
The strategy with HST is to increase the accuracy of our answers to the unknowns at the start of a training cycle. This means decondition the tissue before you start a cycle. This at least allows you to begin on a specific date with less than maximal loads. You then know that each subsequent workout will be slightly less anabolic than the one before, so your goal is to increase either metabolic stress or mechanical stress compared to the previous workout. The emphasis at the beginning of an HST cycle is metabolic stress. This not only acts as a stimulus for growth but also prepares you for heavier loads. The weight progresses steadily over the course of at least 6 weeks in order to stay ahead of the adaptation. Kind of like the way a surfer must stay ahead of the crest of the wave to keep moving forward. The changing rep scheme in HST is simply a reflection of the increasing load, not the other way around.
