Effects of Plyometrics on Human Physiology

Plyometrics are an essential training component for any anaerobic athlete; professional or amateur, that wants to excel. This is because plyometrics greatly increase power, helps nervous fitness and response, and benefits non-specific general fitness. The definition of plyometrics is an exercise in which muscles are completely and rapidly stretched followed by an immediate muscle contraction.

The first reason that plyometrics are such a significant area of training is because they increase the power of your muscles. The two main ways that plyometrics increase power are by increasing muscle strength, and by increasing the speed of contractions. Plyometrics contribute to muscle strength the same way than many other exercises increase muscle strength (VanDyke, n.d.). During exercise muscle is strained and 'ripped', which causes the body to adapt and compensate by building more muscle tissue than previously present. Not only do plyometric exercises contribute to this hypertrophy; they also tone muscle and maintain good muscle composition (VanDyke, n.d.). This is due to the high number of repetitions causing fat to burn, which in turn creates an increase in the ratio of muscle to fat. Although plyometrics increase muscle strength, they are an exercise specifically designed to increase the velocity at which actions may be performed thereby increasing power. By engaging in plyometrics the athlete is entering a brief phase of rapid eccentric contraction before exploding through a concentric contraction (Wilson, 1996). Plyometrics teach the body to enter a 'loaded' state, where the body converts a maximum eccentric contraction into elastic energy, which can instantly be deployed as additional velocity in the following concentric contraction (Chimera, 2004). By training plyometrics muscles adapt for a quicker reloading state (Rimmer, 2000). After a six-week plyometric training program increases in the average height of one-foot take-off and two-foot take-off jumps were demonstrated (Milic, 2008). By combining the training of muscle strength and the speed of contractions, plyometrics create a mechanism where muscle power is increased.

The second reason that programs involving plyometrics are essential to anaerobic athletes that would like to excel is because of the positive effects they have on the nervous fitness of the athletes. Plyometric exercises affect the sensory response of Golgi Tendon Organs (GTO's) and muscle spindles. GTO's are special sensory tendons that are able to sense tension in the muscle, and muscle spindles are receptors located within the muscle that sense changes in length of sarcomeres. Chronic plyometric training is shown to increase the threshold of excitation of GTO's (Brooks, 1996). By raising the threshold the GTO's are less likely to send stretch inhibition signals at higher levels of tension (Brooks, 1996). This consequently means that the muscle cans achieve more tension before a contraction reflex is initiated. By achieving a higher level of tension within the muscle, more elastic energy can be stored and used in the following concentric contraction(Brooks, 1996). This results in a more powerful contraction. Muscle spindles are involved in a different reflex called the 'stretch reflex'. The stretch reflex is activated by quick lengthening of muscle, and ultimately the observed maximum length the muscle can achieve. The stretch reflex is what then causes the next instantaneous concentric contraction. By participating in plyometric activities athletes are actually improving the efficiency of the stretch reflex and also decreasing the latency of nervous pulses(Chu, 1998). Not only are plyometrics involved in various nervous reflexes, they are also involved in general neuromuscular conditioning. Plyometric procedures condition synapses at neuromuscular junctions to fire at uniform times, which increases nervous coordination (Chu, 1998). After consistent plyometric routines for long periods of time the efficiency of signals between the brain and muscle tissue is slightly increased (VanDyke, n.d.). Plyometrics play a large part in nervous fitness by affecting Golgi Tendon Organs, muscle spindles, and nervous coordination.

The final reason that anaerobic athletes wanting to excel should engage in plyometrics is because of the non-specific fitness benefits that come with the routine. Plyometrics have been shown to increase bone density, increase metabolism, and increase agility. Recent studies of the effects of plyometrics on bone density shows that plyometric exercise (PG) increases bone mass in adolescents by 3.7% compared to regular exercise (CG), which increases bone mass by 3.6%. Some areas of significant discrepancies include the mass of the femoral neck (4.5% increase in bone mass of PG compared to 2.4% increase in CG), the