The Navy SEAL Physical Fitness Guide - Uniformed Services ...

Plyometric training is very intense, highly specific,and if done improperly it may be injurious. It shouldnot be routinely incorporated in the Naval SpecialWarfare physical training programs.How Plyometrics WorkPlyometric exercises help to develop explosive strength and speed in fast twitchmuscle fibers. These exercises use the inherent stretch-recoil properties of muscle (i.e.,eccentric tension generated when the muscles are lengthened) to enhance subsequentshortening or concentric contractions. This is the dynamic action behind the rapid prestretchor “cocking” phase to “activate” these natural recoil properties. Examples of thisphase include taking the arm back into position prior to throwing a baseball or bending theknees prior to jumping. Thus athletes that rely on explosive strength and speed, such assprinters and basketball players, include plyometrics in their training programs. Aplyometric movement can be broken down into three phases:" Lengthening phase (eccentric contraction)." Amortization phase." Take-off (concentric contraction).Figure 9-1. ThreePhases ofPlyometrics:Lengthening,Amortization andTake-OffDuring the lengtheningphase, the muscle createstension like a spring beingstretched. This type ofLENGTHENINGTAKE-OFFcontraction, called an eccentriccontraction, occurs whenAMORTIZATIONperforming movements such as jumping down from an object, running downhill, orlowering a weight. During an eccentric contraction, tension is built into the muscle as it160 Plyometrics