This is an excerpt from Strength Training Anatomy Workout, The by Frederic Delavier & Michael Gundill.
How a Muscle Gains Strength
The bigger a muscle is, the stronger it will be. However, you probably know of someone who is very strong but does not have large muscles. How can this paradox be explained? Muscle size is only one of the factors that determine muscle strength. The power of a muscle's contraction depends on the following five things:
1. Number of Motor Neurons Used
A strong person is someone who has the ability to use the maximum amount of his muscle fibers at a given moment. The use of these muscle fibers is carried out by the central nervous system.
Everything starts at the cerebral level: The command given to contract muscles goes through the nerves in the spinal cord. Motor neurons then carry the command to the muscle fibers. Each motor neuron controls the contraction of a specific group of fibers. The more motor neurons that are activated, the greater the quantity of muscle fibers that will contract. This is why training should be done with heavy weights. The heavier the weight you lift, the more motor nerves you will be able to use simultaneously.
2. Strength of the Impulse Sent by Each Motor Neuron
Motor neurons can send electrical impulses to muscles with varying frequency. If the frequency is low, the muscle contracts sluggishly. However, motor neurons can send a flurry of intense impulses that act powerfully on muscle fibers. The intensity of your training develops your capacity to do the most repetitions possible with a heavy weight. Doing plyometrics also plays an important part in increasing the power of nerve impulses.
3. Size of the Muscle
There is a strict correlation between the size of muscle fibers and the strength they are capable of developing. The stronger a section of muscle fibers that is linked to a motor neuron, the more force will be generated by a nerve impulse. You can develop muscle mass by performing weight training exercises with a weight that is around 80 percent of your maximum strength.
4. Intramuscular Coordination
In a sedentary person, when motor neurons discharge their electrical impulses, they do so in a disorderly fashion. The muscle fibers contract in a random, and therefore inefficient, way. Through training, these discharges become synchronized. The fibers begin contracting in a coordinated manner. Muscles become more efficient. You can achieve this by doing weight training exercises with a weight that is close to your repetition maximum.
5. Intermuscular Coordination
It is rare that you have to contract only one muscle at a time. Generally, a whole group of muscles is activated to produce a movement. When resistance becomes greater, the muscles of inexperienced athletes have a hard time working together in an efficient manner. You can see this when such athletes do pull-ups. They lean to one side more than the other. They cannot pull themselves up in a linear fashion and without jerky movements. The body shifts from front to back.
Through training, the quality of movement improves, simply because the arms will have learned to work together with the back muscles, and the muscles on the right side will be in synch with the muscles on the left side.
This gain in efficiency translates to an increase in strength. It is the same in all areas of fitness when you have to learn a new move. It is the volume of work, and therefore the repetition of a movement or an exercise, that improves intermuscular coordination.
Through regular weight training, an athlete's muscles become accustomed to working together. This advanced work means that an athlete can learn new movements more quickly if he has already been weight training for months.
In summary, among the elements we have described, the size of a muscle is just one of five factors of strength. To increase power and strength, your weight training program must also improve the four factors that are part of the central nervous system.
You should glean several practical consequences from these physiological facts:
1. Rapid gains in strength that occur when you start weight training are not because of enlargement of the fibers. They are best explained by improvements in inter- and intramuscular coordination.
2. Therefore, just because you gain strength, at least in the beginning, it does not mean that your weight training program is well structured and that it will continue to help you progress quickly. Someone who is training well can gain strength if only because he is learning to execute movements better.
3. A beginner's gain in strength can be misleading. However, it is still better to gain strength than to lose it. If that happened, it would mean everything was going wrong.
4. You will notice that you are stronger on certain days. The size of your muscles has not changed, so the efficiency of the central nervous system is the explanation for these fluctuations in muscle power. When the central nervous system is well rested, it will demonstrate its efficiency and you will be strong. If the central nervous system has not fully recovered and is tired, then any weight you lift will seem heavier than it actually is.
5. These fluctuations in the central nervous system can create surprises, both good and bad. Before starting a certain training session, you might feel ready to tackle anything, when in fact you are not going to break any of your records. However, there will be days when you feel tired but will be surprised by your own strength because your central nervous system is well rested.
6. A well-rested central nervous system and well-rested muscles do not always coincide. The fact that recovery differs for each makes the task of planning your training that much more difficult.
Read more from The Strength Training Anatomy Workout by Frederic Delavier and Michael Gundill.