specifically the shock method, is considered a form of specialized strength development. Before undertaking plyometric training, it is necessary to distinguish jumps that are commonly called plyometric and true plyometric jumps as exemplified in the depth jump which is illustrative of the shock method. Since its inception in the former Soviet Union as the shock method, there have been other forms of the plyometric exercises created by Yessis that do not involve jump exercises. For details and illustrations of these exercises see "Explosive Running" and "Explosive Plyometrics". These exercises involve the stretch-shorten concept that underlies the shock method. Exercises Squat jump (jumping squat, jump squat): combination of jump (not to be confused with tuck jump) and squat. Squat down then jump off the ground as high as possible, with extended and vertical legs. Tuck jump (tucked jump, tucked knee jump): with feet shoulder width apart, jump, tuck the legs in, extend them, and land. Tuck squat jump: combination of tuck jump and squat jump. Squat down, jump, bring knees up before landing again. Lateral jump: from a standing position, jump side to side. Power skipping: on each skip, lift the upper leg as high as possible. Alternate leg bounding: run with long strides, placing emphasis on hang time. Box jumps: jump onto and off of a large box 18" or higher. Vertical depth jump: starting from the top of a box, jump down and back up as fast as possible. Plyometric push-up (plyo push-up): perform a push up, but exert enough upward force to lift the hands and body off the ground. Broad jump (long jump). Pike jump. Straddle jump (similar to split jumps used by dancers, gymnasts and figure skaters). Lunge jump Method In the depth jump, the athlete experiences a shock on landing in which the hip, knee, and ankle extensor muscles undergo a powerful eccentric contraction. For the muscles to respond explosively, the eccentric contraction is then quickly switched to the isometric (when the downward movement stops) and then the concentric contraction, in a minimum amount of time. This allows the athlete to jump upward as high as possible. In the eccentric contraction, the muscles are involuntarily lengthened, while in the concentric contraction, the muscles are shortened after being tensed. Most of the stretching and shortening takes place in the tendons that attach to the muscles involved rather than in the muscles. To execute the depth jump,