It is simply impossible to train for 14 sets at 85% of your 1 rep max. Just physiologically impossible. Think about it... imagine a bodybuilder such as myself who can, say, squat 475 for 1 rep. But instead I do 404 lbs (85%) for 14 straight sets. How intensely am I training?? How many reps should I be doing? If I do manage to finish my fourteenth set of squats that means I had to hold back on the first sets, three all-out sets of squats within 20 minutes would probably hospitalise most of the population... fourteen sets would kill them.
Well, they recommend 14 total sets per muscle group ... actually they recommend 8 total sets per muscle groups. It doesn't have to be on one exercise. For example it could be:
Back squat 3 sets of 4-6 reps
Leg press 3 sets of 6-8 reps
Leg extension 2 sets of 6-8 reps
For a total of 9 sets.
Now, I will agree that if all of those sets are performed to the point of utmost training failure it will be somekind of challenge. However it can be done provided sufficient rest and adequate physical conditioning.
Still, even sets not conducted to absolute muscle failure can lead to strength and size increases because weight lifting can lead to strength/size gains via several factors:
1. Mechanical and metabolic factors, of which tissue micro-trauma is the main thing. ATP debt is also one of these factor. Both of these can be maximized by training to failure. However performing more sets of near-failure training can build-up to the same amount of muscle micro-trauma and ATP-depth.
2. Hormonal responses to training: hGH and testosterone levels can be modified by training. For example, lactic acid build-up has been linked to hGH release whileheavy lifting has been show to lead to a higher level of testosterone levels. Furthermore, a training program that depletes muscle glycogen has been shown to increase muscle-cell insulin sensitivity, which can increase the anabolic response to post-training feeding. Training to failiure isn't necessary to produce significant hormonal responses, and studies have found that a higher training volume (within reason) leads to a greater hormonal output (to be fair it also increases cortisol output).
3. CNS activation: improving CNS efficiency can facilitate the innervation of fast-twitch motor units by making them more excitable over time. As a result they are more easily recruited and stimulated by training. Since these fibers have a greater growth potential, being able to recruit them more easily will potentiate muscle growth in the long run. High force training methods (heavy lifting or explosive lifting, since force = mass x acceleration) have the greatest impact on the CNS. Training to failure isn't necessary to improve CNS efficiency.
So as you can see, once doesn't have to perform all sets to failure. A set that ends close to failure, but with "1 rep in the tank" will still contribute to strength and size gains despite not going to failure.
If you don't believe the above then simply attach a heavy duty electrostimulator to a bodybuilders quads while he is doing leg-extensions. The muscle can still be stimulated to contract over the rep range long after the bodybuilder has passed out from the pain/stress.
Science! It's fun for all the family!!
The Luke
Actually I do work with EMS with some of my athletes, and while its true that muscles can continue to contract even when voluntary contraction is not possible anymore, this is rarely due to a lack of motivation.
Fatigue from anaerobic work can comes from several sources (lack of motivation being one of them):
1. Acidification of the muscular milieu. When the muscle becomes more acid (due to lactate accumulation), motor-unit activation becomes harder, this is due to a decrease in the excitability of the motor neurons. Since the motor-units/muscle fibers are harder to recruit (so less fibers can come into play), those that can be recruited have to perform more work, get exhausted faster and as a result continuing the set becomes impossible. EMS can then enable the muscle to continue "working" because its impulse is stronger than the CNS nerve impulse and can thus recruit the motor-units that the CNS itself couldn't (because the EMS impulse is strong enough to compensate the decrease in MU excitability).
2. Depletion of the powerful energy substrates. We're talking about anaerobic energy systems, specifically the ATP-CP (phosphagen) and anaerobic glycolysis systems. Both of these can provide ATP (energy) at a very fast rate, but not for long. High intensity muscle work requires such a fast energy production, when these short-term energy stores are unable to produce enough ATP it becomes impossible to continue to produce the same type of muscular effort at the desired level of intensity.
3. The failure to continue a set can also come from excessive micro-trauma (what HIT proponents call "inroads"). In that case the muscle fibers are so severely injured that they simply cannot continue to do the work. This happens only in very rare cases. For example, Brian Johnson (founder of IART and one of the most science-oriented HIT proponent) tested a few subjects on several training protocols (10-10 superslow, 5-5 superslow, 4-2 nautilus protocol) all to muscle failure. He tested the subject's max strength before and after the exercise bout and in several cases (more than 50% of the time) the subjects were actually able to produce MORE force after their work to absolute failure. If failure was due to excessive inroads or micro-trauma, this would have been impossible since tissue restoration takes anywhere between 24 to 72 hours to occur.
BTW, this post is in no way a critique of your training as it seems to be working for you. However understand that many guys suddenly switch to HIT training and have great gains not necessarily because of the superiority of this method but rather:
a) because of what is called "delayed adaptation"... if someone has been training using a very high volume system and suddenly switch to a very low-volume approach, the initial gains on the new program are actually due to a tapering effect: the body finally has time to recover from the *PRECEDING* training stress. The body was bombarded for a while and was never given the chance to recover and grow, and all of a sudden there is a drastic reduction in training stress and now it has time to grow. That initial growth phase is actually the body catching up to what was imposed before changing methods. What then happens is that after 6-8 weeks on the low-volume approach, gains start to stagnate.
Note that a planned version of this approach is often used in sports. Prior to an important competition, coaches will put their athletes through a stress cycle of 1-2 weeks where volume and intensity are both drastically increased to the point that at the end of the cycle, the athletes are borderline overtrained. Then they follow the stress cycle by an unloading or tapering period of the same duration: volume and frequency are both drastically reduced while intensity is maintained. This allows athletes to surcompensate and peak to a much higher level. This is the most often used peaking strategy in swimming events.
b) because someone has stopped training and lost muscle. When he resumes training (using a HIT system or else) the muscle can be regained at a very fast pace (thanks to the plasticity of muscular adaptations). This can give the illusion of superhuman rates of progress.
