Making muscles bigger, stronger, quicker and last longer is the objective of every weight training program. Muscle can be trained to perform at a much higher level than would it be able to if not trained. Building muscles involves overloading them with ever increasing weights and repetitions. The ultimate result is a muscle group that is now adapted to lift heavier weights and to lift it more times and to lift it faster. Adapted muscles, whether it is for a specific sport or for vanity or bodybuilding, are bigger, stronger, and more efficient. An ancillary but equally important (or even more so) effect of directly training muscles is the adaptation and development of the Central Nervous System, or CNS . The CNS is the body system that is responsible for every muscle contraction in the body, and, it too can and should be trained to optimize muscle function. Researchers from Finland performed a study investigating how individual sports background would influence leg muscle contractions during concentric and drop vertical jumps. They discovered that the CNS greatly influenced the firing and recruitment patterns of the muscle based upon the individuals’ specific sport. The participants’ muscles had been trained to contract and fire in a very precise way and pattern as an adaptation to playing and practicing a certain set of movements specific to their sport. Even though they were performing a very basic movement (vertical jumps), the CNS had created specific firing patterns to optimize their performance in a given sport and had thus altered the way they performed other basic functions. In other words, the more you do a specific movement, the better you become at that specific movement and the more natural it becomes. Another way of understanding this is looking back on the first time you attempted a dumbbell bench press in the gym. It was nearly impossible to keep the weights side-by-side and steady as you attempted the lift. You were weak and felt like a fish-out-of-water. However, as you did them more and more, this changed very quickly. Your CNS had adapted your muscles to this lift. Even if a person was completely unable to build muscle for some bizarre reason, he will be able to lift a greater amount of weight simply by training the CNS to recruit more existing muscle tissue and focus the force in the optimal direction. There are two ways to improve strength and muscularity, one is to directly build the muscle, and the other is to train the central nervous system to optimally use existing muscle. Although these two are largely intertwined and it is impossible to train muscle without training the CNS and vice-versa, you can train the CNS to recruit more muscle. The reason this is important to understand is that if you can train your CNS to fire more of its existing muscle cells, you can then use that to build a greater amount of muscle as more muscles will be recruited in all of your movements. There are a few methods that will optimize this muscle recruitment and the result is more growth, bigger and stronger muscles.
The human body is an incredibly efficient machine. This, however, can be detrimental in our efforts to grow muscle mass. In any task, the body will use the least amount of force and muscle tissue to get the job done. For instance, lift your arm out to your side and feel your deltoid, your pecs, traps and other surrounding muscles. Only a small amount of them will be contracted. Now try the same thing holding a heavy weight in your hand and feel the same muscle groups. Many more muscles are now contracted. The same is true of the difference between raising your arm slowly and raising it as quickly and explosively as possible. Even though the movement is identical, the fact that there is increased load (or speed) forces the body to recruit more muscles to perform the task. The more repetitions and the more often movements are performed that recruit a great deal of muscle, the more accustomed your CNS will become to using these muscles, and subsequently, they will be recruited and used more often, leading those muscles to adapt to the training, and grow.
So what are the ideal ways to train the CNS to recruit the most amount of muscle tissue? Research from the Soviet era Institute of Physical Culture found that training with loads in excess of 90% of your one repetition maximum is the best way to increase the number of motor units activated (the most amount of muscle tissue). Loads in excess of 90% of 1RM require that your CNS recruit all available muscles to execute a lift. Similarly, performing a lift as fast as possible has a similar effect. An ideal way to teach your CNS to use as much muscle as possible is to perform some of these lifts, 90% of 1RM and slightly lighter weight with as much explosive acceleration through the lift as possible. This is not to say that this should be the entire workout, rather, 2-4 sets at the beginning of the workout for each target muscle group is ideal. The CNS is different from muscle tissue in that this heavy weight and explosive movement is what creates overload. Your muscles will not feel fatigues at all after 2-3 sets of training like this; however, your CNS will be taxed heavily. After these sets, continue your normal workout with lighter weight, controlled movements, etc. According to science, repetitive execution of this type workout will elicit a greater muscle recruitment and subsequently greater muscle activation throughout the workout.
The other consideration in training the central nervous system is the way in which it fatigues. CNS fatigue is by far paramount to muscle fatigue when it comes to recovery time. The ability of muscle fibers to recover is not a limiting factor in overall recovery. This is primarily the reason a marathoner can run 10-20 miles every single day. You would think that thousands of repetitions of a movement would annihilate the muscles and require long recovery. However, this is not so. However, perform one set of deadlifts at 90% 1RM for 2-3 reps and you may need several days to fully recover. This is because running places very little load on the CNS, whereas the deadlifts are hugely taxing. Tudor Bompa, the father of periodization theory in training and trainer of multiple Olympic medalists recommends 48 hours of recovery in between high intensity CNS workouts. So if you are to do heavy squats one day, its best to do only a moderately CNS taxing workout the following day, like arms etc. This is the reason that you can squat heavy on Monday and come in Tuesday and be weaker on bench press. The pectorals were not used at all, however the CNS has been fatigued and that will result in ALL muscles not firing with as much emphasis until it has fully recovered. Further, Bompa recommends taking 6 minutes in between sets that are designed to optimize contribution of the CNS.
While improved muscle function, size and strength are the ultimate goal, enhancing the ability of the body to use muscles all is equally important. A few heavy (90% 1RM) sets with as much explosiveness as possible and six minutes of rest in between these sets is all that is needed to optimize CNS function and begin recruiting more muscles in your lifts and building more muscle. Any more than this and the CNS is already fatigued and returns will be severely diminished. Incorporate this CNS training into your existing routine for a few weeks and see how you improve.