Nervous System Adaptations

Your body is filled with intricate spiderwebs of nerves that connect every part of your body to the primary nerve center, the spinal cord, and the brain. Every nerve has a different job to do. The nerves that control muscles are called motor nerves. The smallest part of the motor nerve is a single cell called a motor neuron. The neuron has many nerve fibers that branch out to provide nerve impulses to individual muscle fibers. The area of innervation is called the neuromuscular junction (the place where the nerve and muscle join). Although each muscle fiber only has one neuromuscular junction, the motor neuron can innervate hundreds of fibers. The motor neuron and the fibers it innervates are collectively called a motor unit . When the motor neuron is stimulated, all of that motor unit's muscle fibers will contract.

The trick to strength training effectively is to get the most motor units working at one time. The more motor units that are working, the more muscle fibers are contracting, the more force you can produce, and the more training benefits you see in terms of performance and aesthetics. During most daily activities, every motor unit in the muscle doesn't need to be recruited. It takes less muscular force to sit at a computer or drive in a car than it does to lift heavy weight or move a piece of furniture. If these lazy motor units aren't called on for duty very often, then it's a case of use it or lose it. When you introduce weight training, you are calling into action motor units that have never been taxed before. Now the muscle activates fully and becomes more efficient at doing everyday chores as well.

Most of the significant strength gains that you see when you first embark on a weight-training program are due to neural factors. Your nervous system is very good at adaptation. It listens to what you want your body to do and responds appropriately. When you begin training with weights or try any new sport or movement, your nervous system steps up to the plate and does everything in its power to allow you to accomplish the task at hand. It recruits more motor neurons, which in turn recruit more muscle fibers. The increase in fiber recruitment and neural coordination leads to strength gains, without the muscles actually getting bigger (hypertrophy). Even advanced weightlifters have been shown to increase their strength and power, without increasing muscle size, when they change their exercise programs. This phenomenon can only be the result of neural adaptations and increased recruitment.