First of all let's define Speed Training:

Speed training is the capability to increase an athlete’s ability to perform a movement in the shortest period of time. In athletics speed is defined as the ability to perform a movement within a short period of time. Mathematically speed is defined as distance traveled, regardless of direction, over time (s = d/t).

Most all sports require speed, agility and quickness to compete at high levels. Speed training can help an athlete develop hand and/or foot speed, by training the efficiency/coordination of the neuromuscular system and increasing the cross-sectional area of the appropriate muscle fibers.

How fast can a message travel from your brain to the muscles is essential in how fast one can move and react to environmental stimuli. Subsequently, following movements are a combination of both the central and peripheral nervous systems. Sending and receiving neuromuscular information from the muscles to the brain and spinal cord and vice versa needs to be as direct as possible. Think of it as driving on a freeway, there are many off ramps and side streets one can take but there may be faster routes then others. The neuromuscular system is similar, movement will occur in an all-or-none fashion but the path the nervous impulse travels is not always the most direct route. The route may result in the desired movement. However, with proper technique training that route can become the most direct path with the least resistance resulting in faster movement.

From a hierarchical standpoint, the primary method for developing speed and agility is the execution of sound technique. The nervous system may send the impulse to generate muscular contraction, however, the frequency and recruitment of these muscle fibers is just as crucial in efficiency and max force production of the muscle. The greater the number of active motor units, the greater the force production. This being said, our muscles can be trained to fire synergistically and/or in correct sequences to generate the quickest movement or greater force production. Motor unit recruitment patterns can be trained through proper techniques and efficient movement patterns based on ideal athletic movements. Muscle length tensions, proprioception and kinetic awareness are all factors that influence the neuromuscular system.

Now read about applying the proper techniques, drills, and other methods that the pros use to develop muscle speed.

Definition of key terms:
• Motor unit recruitment
• Neuromuscular junction (NMJ)
• Acetylcholine
• Neurotransmitter

Motor unit recruitment is the progressive activation of a muscle by successive recruitment of contractile units (motor units) to accomplish increasing gradations of contractile strength. A motor unit consists of one motor neuron and all of the muscle fibres it contracts. All muscles consist of a number of motor units and the fibers belonging to a motor unit are dispersed and intermingle amongst fibers of other units. The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a weak but distributed muscle contraction. The activation of more motor neurons will result in more muscle fibers being activated, and therefore a stronger muscle contraction. Motor unit recruitment is the principle that the more motor neurons are activated, the stronger the muscle contraction will be. Motor units are generally recruited in order of smallest to largest (fewest fibres to most fibres) as contraction increases. This is known as "Henneman's Size Principle".

A neuromuscular junction (NMJ) is the synapse or junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable surface, ultimately causing region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's the muscle to contract. In vertebrates, the signal passes through the neuromuscular junction via the neurotransmitter acetylcholine.

Motor neuron (efferent) axons originating in the spinal cord enter muscle fibers, where they split into many unmyelinated branches. These terminal fibers run along the myocytes to end at the neuromuscular junction, which occupies a depression in the sarcolemma. Each motor neuron can innervate from one to over 25,000 muscle fibers, but muscle fiber receives inputs from only one motor neuron.

In the terminal bouton of the motor nerve, structures known as presynaptic active zones accumulate synaptic vesicles filled with the neurotransmitter acetylcholine.

On the muscle side of the junction, the muscle fiber is folded into grooves called prejunctional folds that mirror the postsynaptic active zones, the spaces between the folds contain the enzyme acetylcholinesterase.

Acetylcholine, often abbreviated ACh, is a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and the only neurotransmitter used in the somatic nervous system. It is also the neurotransmitter in all autonomic ganglia.

Acetylcholine (ACh) was first identified in 1914 by Henry Hallett Dale for its actions on heart tissue. It was confirmed as a neurotransmitter by Otto Loewi who initially gave it the name vagusstoff because it was released from the vagus nerve. Both received the 1936 Nobel Prize in Physiology or Medicine for their work. Acetylcholine was also the first neurotransmitter to be identified.

Acetylcholine is an ester of acetic acid and choline with chemical formula CH3COOCH2CH2N+(CH3)3. This structure is reflected in the systematic name, 2-acetoxy-N,N,N-trimethylethanaminium.
Acetylcholine has functions both in the peripheral nervous system (PNS) and in the central nervous system (CNS) as a neuromodulator.

Neurotransmitter. Some of the properties that define a chemical as a neurotransmitter are difficult to test experimentally. For example, it is easy using an electron microscope to recognize vesicles on the presynaptic side of a synapse, but it may not be easy to determine directly what chemical is packed into them. The difficulties led to many historical controversies over whether a given chemical was or was not clearly established as a transmitter. In an effort to give some structure to the arguments, neurochemists worked out a set of experimentally tractable rules. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions

Modern advances in pharmacology, genetics, and chemical neuroanatomy have greatly reduced the importance of these rules. A series of experiments that may have taken several years in the 1960s can now be done, with much better precision, in a few months. Thus, it is unusual nowadays for the identification of a chemical as a neurotransmitter to remain controversial for very long.

There are many different ways to classify neurotransmitters. Dividing them into amino acids, peptides, and monoamines is sufficient for some purposes.