Exercise and The Spine
Exercise and Neurological Recruitment
Skeletal muscles can be activated through voluntary effort. They are also under the influence of involuntary control. For example when one muscle contracts another may be neurologically inhibited to relax, an unconscious action by the nervous system. If all muscles contracted in unison (together) we would not be able to move. Through regular exercise and physical activity you can learn to improve the efficiency of muscle contraction. Regular exercise not only changes the pattern of muscle firing but also results in chemical and structural changes within nerves and nerve pathways which influence the muscles. Nerves carry bioelectrical signals from your brain through the spinal cord to muscles to tell them whether to contract or to relax.
You do not have the ability to voluntarily contract every single muscle fiber with a muscle or muscle group all at the same time. The term neurological recruitment (recruitment efficiency) refers to the ability to contract a percentage of a given group of muscle (given group of motor units) fibers with a muscle or group of muscles. The term neurological recruitment, however, refers to the ability to activate a greater number of individual motor units (muscle fibers) within a muscle during a period of time.
Each nerve has an association with certain muscle fibers in what is referred to as a motor unit. The muscle fibers within a muscle are arranged in groups called motor units. A motor unit is defined as a single nerve (alpha motor neuron) and all of the corresponding muscle fibers it connects with or innervates. When a motor unit is activated in the spinal cord, the nerve signal travels out to the motor unit and its entire group of muscle fibers contract. Motor units are called upon to work together to coordinate the contractions of a single muscle. The number of muscle fibers within each motor unit can vary even within a single muscle and between muscle groups. For example, a large thigh muscle may have a thousand fibers in each motor unit whereas a muscle of the eye may only have ten muscle fibers within the motor unit. The later allows for more precise control and activation of the muscle.
Motor units (muscle fibers) are neurologically recruited on an “as needed basis�. The pattern of muscle recruitment is dependant upon the demands placed upon the muscle. The more muscle fibers that can be contracted with a short period of time the more work the muscle can do. The term neurological recruitment or muscle recruitment efficiency refers to the pattern of muscle contraction per unit time. Regular and controlled exercise helps to improve neurological efficiency which enhances physical performance. The recruitment of muscle fibers also occurs in a preferential manner with the smallest motor units usually recruited first followed by the larger motor units. Strength is related to the pattern of motor unit recruitment (neurological efficiency), not just the increased cross-sectional area of muscle (hypertrophy).
For example, imagine that a muscle in the low back has 100 fibers within each motor unit and there are 5 motor units within the back muscle for a total of 500 muscle fibers. An untrained person might only be able to activate 3 of those 5 motor units with a short period of time (giving him a potential of 300 fibers working together), whereas a trained person might be able to activate all 5 motor units simultaneously allowing for all 500 muscle fibers to work together. The person capable of contracting all five motor units simultaneously has more efficient neurological recruitment of muscle fibers and can perform more work with the muscle.
You do not have the ability to voluntarily contract every single muscle fiber with a muscle or muscle group all at the same time. The term neurological recruitment (recruitment efficiency) refers to the ability to contract a percentage of a given group of muscle (given group of motor units) fibers with a muscle or group of muscles. The term neurological recruitment, however, refers to the ability to activate a greater number of individual motor units (muscle fibers) within a muscle during a period of time.
Each nerve has an association with certain muscle fibers in what is referred to as a motor unit. The muscle fibers within a muscle are arranged in groups called motor units. A motor unit is defined as a single nerve (alpha motor neuron) and all of the corresponding muscle fibers it connects with or innervates. When a motor unit is activated in the spinal cord, the nerve signal travels out to the motor unit and its entire group of muscle fibers contract. Motor units are called upon to work together to coordinate the contractions of a single muscle. The number of muscle fibers within each motor unit can vary even within a single muscle and between muscle groups. For example, a large thigh muscle may have a thousand fibers in each motor unit whereas a muscle of the eye may only have ten muscle fibers within the motor unit. The later allows for more precise control and activation of the muscle.
Motor units (muscle fibers) are neurologically recruited on an “as needed basis�. The pattern of muscle recruitment is dependant upon the demands placed upon the muscle. The more muscle fibers that can be contracted with a short period of time the more work the muscle can do. The term neurological recruitment or muscle recruitment efficiency refers to the pattern of muscle contraction per unit time. Regular and controlled exercise helps to improve neurological efficiency which enhances physical performance. The recruitment of muscle fibers also occurs in a preferential manner with the smallest motor units usually recruited first followed by the larger motor units. Strength is related to the pattern of motor unit recruitment (neurological efficiency), not just the increased cross-sectional area of muscle (hypertrophy).
For example, imagine that a muscle in the low back has 100 fibers within each motor unit and there are 5 motor units within the back muscle for a total of 500 muscle fibers. An untrained person might only be able to activate 3 of those 5 motor units with a short period of time (giving him a potential of 300 fibers working together), whereas a trained person might be able to activate all 5 motor units simultaneously allowing for all 500 muscle fibers to work together. The person capable of contracting all five motor units simultaneously has more efficient neurological recruitment of muscle fibers and can perform more work with the muscle.
Regular exercise can also influence the firing rate and pattern of nerves which go to (innervate) motor units within a muscle. With advancing age the loss of motor nerves (alpha motor neurons) leads to collateral reinnervation and remodeling of motor units. Motors units pick up stray muscle fibers resulting in larger motor unit sizes. Exercising during this process has positive impact on the outcome. Sophisticated technology (devices) has also been developed to perform this type of training.
It is important to constantly vary the type of exercises performed to stimulate greater gains and to improve neurological efficiency. This can be accomplished by changing the type of exercise, modifying the speed of application, altering the order of the exercises or simply by modifying the way a particular exercise is performed. This is also easily accomplished through unstable base training. The most common form of this is the use of the exercise ball or working out on a balance platform.
It is important to constantly vary the type of exercises performed to stimulate greater gains and to improve neurological efficiency. This can be accomplished by changing the type of exercise, modifying the speed of application, altering the order of the exercises or simply by modifying the way a particular exercise is performed. This is also easily accomplished through unstable base training. The most common form of this is the use of the exercise ball or working out on a balance platform.