At it’s core, acceleration is the rate at which a body changes velocity. In the body, acceleration is the rate that a muscle contraction occurs. In pitching, rapid acceleration occurs almost everywhere. The term “relaxing into rotation,” often used to describe the action of the pelvis and the back leg, should actually coined “relaxing into acceleration”.
A muscle contraction is triggered when an action potential travels along the nerves to the muscle. The impulse, also called action potential, travels through a motor neuron to a neuromuscular junction where the chemical signal is released by the motor neuron. The chemical signal binds to receptors on the muscle fiber and contraction begins.
There are several factors that inhibit acceleration: central nervous system (CNS) fatigue, the inability to decelerate, and a lack of relaxation.
CNS fatigue is the inability to maintain a given exercise intensity. This can occur during long bouts of exercise, or can even prevent optimal performance days later. Overall, the ability to maintain CNS drive to the working muscles is compromised. During CNS fatigue it takes more stimulation to produce a desirable amount of muscle contraction. There are several neurophysiological mechanisms to explain CNS fatigue: a reduction of descending impulses reaching the motor neurons, and prevention of motor neuron excitability caused by feedback from the muscle. CNS fatigue reduces the strength of impulses created by the brain, and muscle fatigue inhibits the excitability of the motor neuron therefore limiting the strength of the contraction.
The second factor that may be impacting acceleration is the body’s inability to decelerate at the desired speed. The brain’s first priority is survival, and at a primal level injury is the most likely factor that would prevent the body from surviving. Exerting more force than the body can tolerate could potentially lead to strains and tears that would limit the body from optimal functioning. One of the main mechanisms that prevents this are the golgi tendon organs (GTO). GTO measure the force being placed on the muscle and tell the body when to relax, therefore limiting the strength of the contraction. GTO can be overridden, when a mother lifts up a car to save her baby, or when the body enters such a sympathetic state and the body will do anything it can to survive even if it means injuring itself.
Relaxation is the quickest way to create acceleration within the body. For now, lets just look at two different muscles that are antagonists (muscles that perform opposite actions of each other). The triceps brachii performs elbow extension, and the biceps brachii performs elbow flexion. The main factor that can prevent the speed of elbow flexion is activation of the triceps brachii. Relaxation and activation of the correct muscular groups can be one of the easiest ways to create acceleration.
While training for increased velocity and movement efficiency on the mound, each of these factors can present itself. Overtraining in the weight room or throwing can lead to CNS fatigue that decreases velocity within the throwing session, or during several consecutive throwing sessions. Allowing for adequate rest and deloading will remedy most issues in this area. GTO training can be done with eccentric exercise, and inherently becoming stronger and training at high velocity can have the same effect. In the pitching delivery, a pitcher is not relaxed while muscling up. Relaxing until in the proper time and waiting for the buildup of tension is a much easier way to create velocity, and is much less taxing on the body and CNS. The term “relax into rotation,” is not just saying relax and then fall down the mound at the last second. It is implying that there should be relaxation of the correct muscles until the contraction needs to occur so there is not inhibition of the potential speed of rotation or contraction.
Acceleration is key. 95 or die.
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