[Warning, long post. Old and Grey, if you want you can skip to the last paragraph. Everything in the middle is just scientific rambling. ]
Old and Grey,
First off, great question. Surely there must be something there for hypertrophy-specific lifters otherwise these guys wouldn’t be trying to come up with new methods that basically achieve the same thing. I believe that what they are trying to achieve is two fold, 1) maximum recruitment of motor units, and 2) high metabolic stress.
I won’t get into the first issue right now. I’ve addressed it before with little avail. In short, maximum recruitment of motor units does not seem to require maximum fatigue or maximum loads. Other wise, we would only see hypertrophy in studies using 100% 1RM weight loads, and this is clearly not the case. The overwhelming majority achieve the highest rates of hypertrophy in the 60-75% range with pre-conditioned or untrained lifters. Some studies have produced results with less and others have produced results with more, but the ball park is clearly 60-85% to cover even veteran lifters.
As for the second point, metabolic stress, this issue has come to the forefront in research circles because of all the “occlusion” studies. Occlusion studies set up a lifting condition in which the blood flow is blocked or severely reduced to the working muscle, usually by using a tourniquet. These studies often incorporate as little as 20% 1RM for the load yet still produce respectable increases in strength and on occasion hypertrophy. Once again, these studies use pre-conditioned subjects as a general rule.
There was published in 2005 an influential study by Goto in Med Sci Sports Exerc. (Goto K, et al. The impact of metabolic stress on hormonal responses and muscular adaptations. Med Sci Sports Exerc. 2005 Jun;37(6):955-63.) This study compared two methods of completing a fix number of reps (10) with a fixed weight load (75%1RM). One group did all 10 reps all the way through till the last rep, then rested as you normally would for 1 minute before the next set. This is the traditional way we lift as well. The second group, used the same relative weight loads, but half way through each set, they would stop and rest for 30 seconds before finishing the set. This was done in an attempt to reduce the metabolic demand of the set.
So basically you have one group doing 3 sets of 10 reps with their 10RM. You are comparing their results with another group doing 3 sets of 5 with their 10RM.
Their results showed a ~13% increase in muscle cross sectional area in the no-rest group and a ~4% increase in the rest-midway group.
This study, along with the vascular occlusion studies as driven academics back to the “it’s the burn” the causes hypertrophy mindset. (They seem to have forgotten the years of research showing superior hypertrophy produced by eccentric contractions that produce little metabolic stress compared to concentric contractions.)
I personally believe that metabolic disturbances within the muscle facilitate muscle hypertrophy in untrained subjects but are not sufficient to cause hypertrophy in well trained lifters. It’s like saying ketchup is really what defines a burger, as a burger, not the beef patty and bun. Sure, the ketchup makes a burger easier to enjoy, but it isn’t really what defines it as a burger. And focusing on different condiments is what Old and Grey perceives is going on with all the different lifting styles he mentioned.
Before I finish this overly long post let me say there has been plenty of consensus and corroboration since Goldberg (Goldberg, 1975) first postulated that load itself could induced muscle hypertrophy. Not only that but much work has been done to elucidate the phenomena further.
In muscle cells, the ability to perceive and respond to mechanical load is called “mechanoperception”. This process of converting the mechanical signals of lifting a weight into the biochemical signals that lead to hypertrophy is called mechanotransduction (Hornberger, 2004). Muscle cells, in turn, are called “mechanocytes”. This simply means that muscle cells have the ability to sense mechanical load and convert it into biochemical signals that regulate protein synthesis. Terms such as “mechanotransduction” and “mechanocyte” are now common in research about all kinds of cells that respond to being pulled and stretched. Everything from skin to blood vessels use mechanotransduction.
The process of mechanotransduction in skeletal muscle is pretty straight forward. Let’s say for example that you are doing bicep curls. As you lift the weight, the load of the dumbbell is transferred from your hand to the insertion of the biceps on up through the length of the muscle. It’s this stretch, or strain, that initiates the signaling cascade that ends in muscle hypertrophy (Zanchi, 2008). One thing to mention here is that this process does not necessarily require significant fatigue, although fatigue can change the distribution of the strain. And metabolic disturbances within the muscle certainly improve the anabolic stimulus in a number of ways, some of which may involve adapting to maintain higher cellular energy reserves to fuel high rates of protein synthesis.
Ok, that plenty of typing just to say, I agree with you Old and Grey.
It is the HST principle that the metabolic disturbance created towards the end of a set with a sufficient number of contractions facilitates muscle hypertrophy and any good hypertrophy-specific approach should allow for any of a number of methods to produce those metabolic disturbances be it drop sets, rest pause, burn-out set, short rest sets, etc, etc.
-bryan
References:
Goldberg AL, et al. Mechanism of work-induced hypertrophy of skeletal muscle.
Med Sci Sports. 1975 Fall;7(3):185-98.
Hornberger TA, et al. Mechanotransduction and the regulation of protein synthesis in skeletal muscle.
Proc Nutr Soc. 2004 May;63(2):331-5
Zanchi NE, et al. Mechanical stimuli of skeletal muscle: implications on mTOR/p70s6k and protein synthesis.
Eur J Appl Physiol. 2008 Feb;102(3):253-63.
Dentons work Journal of Strength and Conditioning Research, 2006, 20(3), 528–534 looking how intra-set rest impacts the amount of work achieved it's pretty apparent that adding in brief rest during a set can change not only the amount of work performed but also the force per rep.