I've seen the effects of your more frequent, short duration, strength training and I attempt to incorporate the great things I see on your website into our PT program (ie. Tire pull, HMMWV push). However, your website states that your training can increase muscle recruitment and myofibril density. I've scoured the physiology journals and cannot understand what you are doing to cause this. Can you please explain this to ensure I'm doing the right thing in my platoon's PT?
Thanks for your time.
First of all the Gym Jones "program" (for lack of a better term) is not fixed and one size does not fit all. Second, the definitions.
As a broad descriptive term Muscle Recruitment may refer to a couple of things: Sequential firing, what motor units must fire in what order to complete the movement. The more functional the movement (in the gym) the more "specific" the recruitment pattern achieved in the artificial training environment. E.G. a squat is more functional than a leg press on the machine due to the three-dimensional stabilization (balance, etc) required by the squat vs. only pressing on single plane and likely being seated when doing the work on the machine.
Next, Muscle Recruitment may also describe the quantity of fibers being stimulated to engage in the effort. The normal person can recruit 30% of existing muscle fibers to move a load, the trained athlete recruits up to and sometimes a bit more than 50%. When hit by lightning 100% may be recruited. The key to increasing recruitment (in quantity), which increases the weight/volume efficiency of the muscle is to make well-rested muscles move 1RM to 2RM loads. This doesn't necessarily happen in a circuit it occurs on specific recruitment (power) training days. That said, plyometric and ballistic loading also increase recruitment by loading an already contracted muscle. Recruitment demanded by great loads is essentially neuro-muscular training (CNS), heating up the neural pathways so that communication between brain and muscles is as efficient as possible. And CNS inhibition is reduced by training with maximal loads.
This leads to the next concept that may be described by Muscle Recruitment, which is timing, and in this case I use it to explain what must occur at the bottom of a depth jump, the reversal of a KB or DB swing (at the bottom), absorbing the impact of the incoming medicine ball, etc. The best example might be the "snap" at the moment of reversal during the KB swing, when all muscle in the body must fire at the same time to absorb the force of the descending KB and turn it directly around and into upward motion. Another thing to consider is that muscle fibers have different recruitment thresholds in different movements: motor units that are difficult to recruit in one movement pattern may be more easily recruited by a different movement pattern. This is the specificity of training effect. But if you want to fully develop the muscle rather than simply training it to do a sport-specific pattern then you must work it in all possible ranges of motion, and full ROM at that.
I would rather build athletes with the greatest power-to-weight ratios possible. Most have to carry whatever muscle they have for sport or work so we do work that makes the existing muscle as efficient as possible rather than manipulating work/diet to build more muscle. The goal might be to build an athlete weighing 155 who can do pull-ups with +100# hanging from him, can deadlift more than 2x bodyweight, and can also go non-stop for 24 hours. One cannot develop such high power-to-weight ratios without lifting big loads. However, one can increase the efficiency of the neural communication pathways by training the movements at low loads. Some very big deadlifts have been put up on a diet of 3x 20 DLs @ 25-30% of 1RM 3-4 times per week and lifting heavy (1RM) one time every three weeks. Circuits that include functional movements reinforce muscle memory for the movement (and also have the benefit of improving metabolic capacity) then 1RM lifts using those same movements stimulate increases in recruitment (volume, synchronicity, timing), and reduce CNS inhibition.
Another result of the 1RM or Max Effort training is the increase in myofibril density. This requires training with heavy loads (heavy for the individual not whatever the consensus definition of "heavy" might be). Again, rested muscles are prerequisite and training to failure, especially eccentric failure strictly forbidden.