Training a muscle every 48 hours really IS optimal for growth...

[HST_Rihad]

Come on, guys, the recommendation to train each MG *at least* three times a week is all throughout the HST FAQ, Brian has mentioned it several times.

T: What's the advantage of whole-body workouts? Those are really out of style these days, so to
speak.
BH: The advantage doesn't lie in the fact that you're training your whole body all at once. The
important thing is to be able to train each muscle group every 48 hours. This generally means
three evenly spaced sessions per week. Training each muscle group every 48 hours necessitates
training more muscle groups at a time, or going back to the gym more often. Either way works.

Now, considering that training only elevates protein synthesis for about 36 hours, and muscle is
able to be trained again within 48 hours without negatively effecting recovery, training a
muscle every 48 hours becomes a viable and desirable method to maximize the rate of muscle
growth.

HST uses this evidence and calls for repeated loading (training) every 48 hours or so to keep
the anabolic activity of the muscle high, while trying to stay slightly ahead of the structural
recovery curve by constantly increasing the load each workout. Staying ahead of the structural
recovery curve is really key in eliciting growth in a person who's lifted for quite some time.

In summary, to apply the principles of hypertrophy just explained, you're going to:
• Train each body part every 48 hours, or basically three times per week.
• Increase the weight each and every workout.
• Decrease the reps every two weeks.
• Decondition the muscle before you do it all over again.

(are these the four principles Totentanz talked about?)

[CDB]

Come on, guys, the recommendation to train each MG *at least* three times a week is all throughout the HST FAQ, Brian has mentioned it several times.

He said it's 'advisable' and desirable. Not necessary at the cost of the universe and all possible muscle gains. And as I mentioned before, if the 48 hour rule is inviolable then why exercise three times a week when you would have to exercise four times one week, three the next, four the next, etc. to respect the all powerful 48 hour rule? So if he's already recommending a practical compromise in three times a week (leaving a 72 hour period where, gasp!, you don't workout...), then I guess it wasn't that hard of a 'rule' to begin with, was it?

[T-man]

More guideline than rule for the sake of consistency, IMO.

[Totentanz]

HST PRINCIPLES

1) Mechanical Load
Mechanical Load is necessary to induce muscle hypertrophy. This mechanism involves but isn't limited to, MAPk/ERK, satellite cells, growth factors, calcium, and number of other fairly understood factors. It is incorrect to say "we don't know how muscle grows in response to training". The whole point of the HST book is not to discuss HST, but to present the body of research explaining how hypertrophy occurs. Then HST becomes a relatively obvious conclusion if your goal is hypertrophy.

2) Acute vs. Chronic Stimuli
In order for the loading to result in significant hypertrophy, the stimulus must be applied with sufficient frequency to create a new "environment", as opposed to seemingly random and acute assaults on the mechanical integrity of the tissue. The downside of taking a week of rest every time you load a muscle is that many of the acute responses to training like increased protein synthesis, prostaglandins, IGF-1 levels, and mRNA levels all return to normal in about 36 hours. So, you spend 2 days growing and half a week in a semi-anticatabolic state returning to normal (some people call this recovery), when research shows us that recovery can take place unabated even if a the muscle is loaded again in 48 hours. So true anabolism from loading only lasts 2 days at best once the load is removed. The rest of the time you are simply balancing nitrogen retention without adding to it.

3) Progressive Load
Over time, the tissue adapts and becomes resistant to the damaging effects of mechanical load. This adaptation (resistance to the stimulus) can happen in as little as 48 hours (Repeated Bout Effect or Rapid Training Effect). As this happens, hypertrophy will stop, though neural and metabolic adaptations can and may continue. As opposed to hypertrophy, the foundation for the development of strength is neuromuscular in nature. Increases in strength from resistance exercise have been attributed to several neural adaptations including altered recruitment patterns, rate coding, motor unit synchronization, reflex potentiation, prime mover antagonist activity, and prime mover agonist activity. So, aside from incremental changes in the number of contractile filaments (hypertrophy), voluntary force production (i.e. strength) is largely a matter of "activating" motor units.

4) Strategic Deconditioning
At this point, it is necessary to either increase the load (Progressive load), or decrease the degree of conditioning to the load (Strategic Deconditioning). The muscle is sensitive not only to the absolute load, but also to the change in load (up or down). Therefore, you can get a hypertrophic effect from increasing the load from a previous load, even if the absolute load is not maximum, assuming conditioning (resistance to exercise induced micro-damage) is not to extensive. There is a limit to the number of increments you can add to increase the load. You simply reach your maximum voluntary strength eventually. This is why Strategic Deconditioning is required for continued growth once growth has stopped (all things remaining equal).

These are the four principles. Notice in #2 how he states that taking a week break for a muscle group is suboptimal. Stated as thus "So, you spend 2 days growing and half a week in a semi-anticatabolic state returning to normal (some people call this recovery), when research shows us that recovery can take place unabated even if a the muscle is loaded again in 48 hours" So he doesn't say "must train every 48 hours" but says that a muscle that has already been worked can be loaded again in 48 hours. And in the example HST setup, he has you working out Monday, Weds and Friday - as CDB pointed out, this would not have you lifting every 48 hours. That would require four days one week, three the next and that is not how Bryan set up the example HST routine. If it were a hard and fast rule, don't you think he would have stuck by the rule? Notice how in the quote that you posted, Rihad, Bryan even states the following - emphasis is mine:

HST uses this evidence and calls for repeated loading (training) every 48 hours or so to keep
the anabolic activity of the muscle high, while trying to stay slightly ahead of the structural
recovery curve by constantly increasing the load each workout. Staying ahead of the structural
recovery curve is really key in eliciting growth in a person who's lifted for quite some time.

Every 48 hours or so. Or so.
The whole point of Bryan's words in the FAQs and the articles was to illustrate that higher frequency than the standard bodypart split is better. In the standard bodypart split, you lift 4-5 times a week and only hit one muscle group each workout, so you are only hitting muscle groups once a week. That means that any routine that has you hitting a muscle group twice or more a week would satisfy the "acute vs chronic stimuli" principle.

[AlexAustralia]

Somewhat begs the qn about why do ppl force themselves into a M-W-F (for example) split rather than just accepting 'every 48hrs'; think in terms of actual frequency and not frequency using 'per week' as the unit.

[T-man]

Convenience, work, family obligations, wanting a balanced life, etc.

[CDB]

Since I may have over stepped on the troll thing, it boils down to this: any program that produces muscle growth is technically 'an HST' workout, or at least in adherence to the guidelines because they are broad enough to encompass damn near anything that isn't completely retarded. And for good reason, because any workout that isn't completely retarded will generally produce results. The point of HST is to pull apart the fundamentals of why these programs work, and what might be compromised in them, and give people a framework to optimize according to their needs.

Think of it in terms of an iPhone or Android app. The top portion of the screen is the output, where the workout program comes out. The bottom part has sliders and what not to adjust to alter the outputted program. HST principles would be the four major controls that you slide up and down from 1 to 10 to adjust their relative importance to you and the context in which you are currently working. The point really is now we know what it is we're adjusting instead of just randomly jumbling things around with reps and volume and sets and load.

[Totentanz]

Well said.

I think it is also worth noting that when Bryan came up with the standard HST routine (which is meant to be just an example...) in the HST articles, that really was meant to just be a one-size-fits-all type of thing that would work for the majority of people. Of course there are other things you could do that would still work just as well. As CDB pointed out, HST is about the fundamentals. We are talking about the science of muscle growth. Any routine that causes growth is going to be meeting at least some of the criteria, because the rules of what causes growth are going to be the same for everyone. Some variables will change from person to person but not radically so.
This is why you will see people doing routines that include a lot of different things but still calling it HST. Or why you will see people saying that a certain routine (such as DC, or 5x5, or some others) are variations of HST - because if a certain system or routine is a good one and actually works, then it pretty much has to be following the principles of HST. Remember, these principles are based on actual scientific research.

[AlexAustralia]

Convenience, work, family obligations, wanting a balanced life, etc.

Oh for sure. I'm not suggesting anyone detail their lives around their workouts.

The conundrum, I think, is that people start confusing 'optimal' rest periods between work-outs with organising their workouts into the (v.strange) 7-day week structure the world uses. The body doesn't 'think' in terms of M-T-W-T-F-S-S.

[CDB]

Oh for sure. I'm not suggesting anyone detail their lives around their workouts.

The conundrum, I think, is that people start confusing 'optimal' rest periods between work-outs with organising their workouts into the (v.strange) 7-day week structure the world uses. The body doesn't 'think' in terms of M-T-W-T-F-S-S.

People do indeed do that. People also do a lot of other stupid stuff. It's missng the forest for one pine needle. The most important principle of them all is chronic vs accute stimulus. It trumps everything, because even if your workout is ridiculous, if you stick with it for the long term you'll probably see some sort of gains. The research behind HST and other workouts like Max Stim actually belies their purpose: simplicity. They're trying to get down to the fundamentals so people like us can see things more clearly thanks to their work. And while the biomechanics of muscle growth are complex as hell, the practical application to achieve it is as simple as can be: lift progressively heavier stuff over time, do it as frequently as you can manage, and eat.