Contractile Mechanisms
The contractile mechanisms within the SSC are thought to enhance performance by directly contributing to the amount of force generated, which stretches the elastic components of the muscle. They seem to play a greater role in longer-duration plyometric actions.
The active stretch phase of a plyometric action acts as a potentiator for the MTU. The stretch-tension applied to the muscle removes unwanted slack from passive tissues; helping to creating a stiffer “active” system which is favourable for powerful performance.
Increased coupling time is thought to play an important role in longer-duration SSC actions due to the time taken to achieve peak force (0.7 seconds). The extended time under tension allows for cross-bridge interaction to take place.
An interesting quality of the of these cross bridges is their ability to act as a catch-like mechanism within the muscle; slowing down the speed of contractions, allowing high force to develop within the muscle and tendons to stretch during eccentric and isometric phases. This means the explosive concentric phase begins with a larger amount of force. This momentary pause allows the central nervous system (CNS) to send electrical signals which release; or fire; as many motor units as possible within the muscle. Although this may result in a slightly longer activation time, or shortening velocity, the resulting impulse will be greater and performance will be improved.
The active stretch phase of a plyometric action acts as a potentiator for the MTU. The stretch-tension applied to the muscle removes unwanted slack from passive tissues; helping to creating a stiffer “active” system which is favourable for powerful performance.
Increased coupling time is thought to play an important role in longer-duration SSC actions due to the time taken to achieve peak force (0.7 seconds). The extended time under tension allows for cross-bridge interaction to take place.
An interesting quality of the of these cross bridges is their ability to act as a catch-like mechanism within the muscle; slowing down the speed of contractions, allowing high force to develop within the muscle and tendons to stretch during eccentric and isometric phases. This means the explosive concentric phase begins with a larger amount of force. This momentary pause allows the central nervous system (CNS) to send electrical signals which release; or fire; as many motor units as possible within the muscle. Although this may result in a slightly longer activation time, or shortening velocity, the resulting impulse will be greater and performance will be improved.
Neural Mechanisms
This is probably the most complicated area of the science behind Plyometric training, so don't worry if you get a bit lost here!
Sensory receptors act as a defence mechanism for muscles, picking up information and feeding back to the CNS via afferent neurons. The CNS then responds with an efferent output. Within the SSC it is the short-latency monosynaptic reflex which is activated when muscle fibres are stretched. When stretched, the muscle spindles respond by discharging action potentials towards the spinal cord. The protective response of the CNS is to innervate alpha motor neurons which contract extrafusal muscle fibres and shorten the muscle.
Golgi tendon organs (GTOs), situated at the musculotendinous junction send out 1b afferent responses to the CNS which can inhibit force potentiation signals (autogenic inhibition). Plyometric training has been shown to reduce these inhibitory effects, enabling athletes to sustain increased landing forces without a decrease in force production.
Sensory receptors act as a defence mechanism for muscles, picking up information and feeding back to the CNS via afferent neurons. The CNS then responds with an efferent output. Within the SSC it is the short-latency monosynaptic reflex which is activated when muscle fibres are stretched. When stretched, the muscle spindles respond by discharging action potentials towards the spinal cord. The protective response of the CNS is to innervate alpha motor neurons which contract extrafusal muscle fibres and shorten the muscle.
Golgi tendon organs (GTOs), situated at the musculotendinous junction send out 1b afferent responses to the CNS which can inhibit force potentiation signals (autogenic inhibition). Plyometric training has been shown to reduce these inhibitory effects, enabling athletes to sustain increased landing forces without a decrease in force production.
Plyometric training = Reduced inhibitory effect of GTOs = Increased potentiation of muscle spindles