Nervous System Adaptations

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Nervous System Adaptations

Your body is filled with intricate spider webs of nerves that connect every part of your body to the primary nerve centre, 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 fibres that branch out to provide nerve impulses to individual muscle fibres.

The area of innervation is called the neuromuscular junction (the place where the nerve and muscle join). Although each muscle fibre only has one neuromuscular junction, the motor neuron can innervate hundreds of fibres as in the case of the quadriceps or only a few fibres, in the case of the eye. More intricate movements that require a high level of control (as in the eye) will have a lower ratio of fibre: motor neuron. The motor neuron and the fibres it innervates are collectively called a motor unit. When the motor neuron is stimulated, all of that motor unit's muscle fibres will contract.

Effective strength and power training will be characterised by getting the vast majority of motor units firing at one time. The more motor units that are working, the more muscle fibres 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 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 fibres. The increase in fibre 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 and the inhibition of the Proprioceptors found in the muscles and surrounding tissues such as the Golgi Tendon organ.

The GTO’s are located in tendons near the myotendinous junction and are activated when a muscle is stretched. During heavy lifts, increased tension from the stretch results in increases discharge of the GTOs and its sensory neuron activates the inhibitory neuron of the spinal chord resulting in a decrease of muscle tension (hopefully no injury!).