I've read the time under tension article, and I'm wondering if I'm over thinking this..
Based upon what it says, ideally a set should be 30-60 seconds long for hypertrophy. This seems a little unrealistic when doing sets of 6 reps - each rep would have to be between 5 and 8 seconds long. So, am I letting a less-important thing (tut) distract me from a more important thing (hct-12)? Maybe tut is more of an advanced lifting thing, and if so, that's fine. I'm just wondering about it.
"A man can no more diminish God's glory by refusing to worship Him than a lunatic can put out the sun by scribbling the word, 'darkness' on the walls of his cell." ~ C.S. Lewis
Quoting the author -
A sufficient amount of muscular tension is necessary to elicit a physiological adaptation to weight training.Weight training is essentially training the brain (nervous system) how to recruit motor units. Without losing too many people, a motor unit is a motor neuron and all the muscle fibers it innervates (5). There are 2 primary classes of muscle fibers: Type I, and type II. The type I fibers are referred to as slow-twitch. These fibers contract slowly and are harder to fatigue (6). These are the fibers primarily used when lifting light loads. The type II fibers are referred to as fast-twitch. They contract very rapidly and fatigue very quickly. Fast-twitch fibers can be broken down into types IIa and IIb. Type IIa fibers fatigue moderately and have properties of both type I and IIb fibers. Type IIb fibers fatigue easily and are used for short, high-force production tasks such as lifting heavy weights, sprinting, or jumping (6).
The fast-twitch fibers are primarily affected by lower rep sets. A decreased TUT will be used to stimulate these explosive muscle fibers, without causing too much fatigue to the nervous system. With this type of training, the brain is learning to synchronously recruit motor units in an attempt to perform the exercise.
This is why the speed of movement is very crucial. If you were to attempt to perform a set of 10 reps on the bench press, performing the concentric (positive) portion of the lift as fast as possible regardless of load, it would be impossible to replicate the same velocity on each rep. Consequently, fatigue results, and the quality of work is compromised. If the number of reps were limited to 2 or 3, the quality of work would be much higher.
Conversely, if you are training for hypertrophy (where an increase in muscle size is the main goal), then a greater time must be spent under tension to elicit a GH response, fatigue motor units, and produce contractile breakdown of muscle tissue. This will help to provide the body with a stimulus for muscle growth.
Another important issue to mention at this time is a concept referred to as Compensatory Acceleration Training (CAT). CAT assists in creating a greater amount of muscular tension by voluntarily attempting to recruit the fast-twitch motor units (10). When using this in your training, you must attempt to accelerate the weight as fast as you can during the concentric part of the lift. Donít worry if the weight is heavy or moderate, if your intent is to move the implement as fast as you can, a greater proportion of fast-twitch motor units will be recruited. This is very important to athletes that perform in sports where speed is a determining factor. This can also benefit bodybuilders. The fast-twitch muscle fibers have a greater ability to hypertrophy. What better than a way to attempt to recruit them on every single rep
Anyway the author concedes that there is a threshold tension that needs to be reached in-order to stimulate growth and that this threshold is the tension required to recruit the High Threshold Motor Units, the ones most able to grow (in fact in people worry too much about training for different fiber types depending on their particular make-up. Fact is the only fibers you will hypertrophy to any degree are those contained in the HTMU's. So it makes no sense other than to train them, irrespective of one's perceived muscle make-up).
The threshold is approx 70% 1RM . The intensity at which the HTMU's are recruited from the first rep is approx 80-85% 1RM
I'm quoting me here -
Time under tension when applied the way suggested in that article would require using less weight i.e. a reduction in tension which is a reduction in the number of HTMU's recruited and fatigued (the two primary stimuli for growth) less work done and less power output.HOW HEAVY SHOULD THE WEIGHT BE?
I detailed above that the higher the load, the greater the tension, the greater the number and size of the Motor Units recruited to lift the load and the greater the potential growth.
In the gym, that load works out to be between 70% and 90% of 1RM (Rhea et al. 2003, Peterson et al. 2004,2005 and Wernbom et al. 2007), which translates to a rep range of roughly between 15RM and 5RM. So getting stronger anywhere between 70% and 90% 1RM (15RM and 5RM) is going to effectively stimulate growth.
We can however narrow it down further by looking into the two factors responsible for strength production:
1) Muscle Fiber Recruitment - We covered this above in Motor Unit Recruitment.
2) Rate Coding - In part this was covered above. Messages sent by the Nervous System control muscle contraction. Rate Coding refers to how fast those messages are sent. The faster theyíre sent, the stronger the contraction.
Up to about 80-85% 1RM, youíll be relying on Motor Unit Recruitment. Above that, Rate Coding Kicks in (i.e. no further Motor Units will be recruited), the fibers will just be made to contract harder. So at around 80-85% 1RM youíll recruit every Motor Unit you have, which for all intents and purposes means all the muscle fibers. Below 80-85% 1RM, the largest Motor Units are activated only as the muscle fatigues (toward the end of the set). Given the largest MUs have the greatest potential for growth; it makes sense to recruit them from the first rep. So that narrows our rep range even further to between 5RM-8RM.
Not sure if that answers the question to your satisfaction. And to be clear, my points and the science behind my article support all effective programs not just HCT-12, so there's no agenda there, so feel free to ask me to elaborate further.
Last edited by Daniel Roberts; 10-19-2010 at 08:55 AM. Reason: Issues with quoting and highlighting!