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Home , Plyometrics, Strength training

Introduction to Plyometrics: Converting Strength to Power Ed McNeely, MS

ower, the combination of speed The Stretch Shortening Mechanisms and strength, is crucial for suc- Cycle (SSC) Behind the SSC cess in many sporting events. Muscles are capable of three types of Th e stretch shortening cycle results in PTh e purpose of plyometric work is the more powerful concentric contractions. contraction. same as that of , to How does this happen? Th ere are two develop greater physical power. Many 1. Isometric contraction in which mechanisms that help to contribute athletes spend all their time in the the length of the muscle does not to the explosive concentric contraction weight room trying to increase power change these are the elastic potential of the with and dumbbell . muscle and the muscle spindles. Th e 2. Concentric contraction in which While these exercises have their place, the muscle is shortened muscles contain elastic fi bers made up they are not the most effi cient means of a called elastin. Th ese fi bers 3. Eccentric contraction in which the of developing power. Traditional weight are easily stretched and return to their muscle is lengthened room exercises do not allow the athlete original length. Th ey function similar to to move at the speed, or use the move- a rubber band and when stretched can ments needed, to develop sport specifi c In normal activity, these contractions add to the power of a movement. Since power. seldom occur alone. Due to the infl u- much of the original research into the ence of gravity, compression and impact SSC was done on isolated muscles fi bers While strength training can create the forces, from and jumping that had been removed from a frog, the muscular and nervous system adap- activities, there is usually an eccentric elastic response was thought to be the tations necessary for power develop- contraction followed by a concentric main cause of the greater power output. ment, plyometrics focuses on the speed contraction. Th is combination of eccen- However, the muscle spindle also plays a component of power and transforms tric-concentric contractions is known as role when living muscles are activated. the physiological changes into athletic the stretch shortening cycle. Th e addi- ability. It does this through the use of tion of an eccentric contraction prior to Muscle spindles are located within a the elastic properties of muscle and the a concentric contraction has been found muscle near the point that it joins the stretch shortening cycle. to increase the force, speed, and power . A spindle consists of a modi- output of the concentric contraction. fi ed fi ber with a sensory nerve wrapped around one end of it. Th e muscle spindle senses changes in the amount of stretch in a muscle. A

NSCA’s Performance Training Journal | www.nsca-lift.org/perform Vol. 6 No. 5 | Page 19 Introduction to Plyometrics: Plyometrics Converting Strength to Power signal is sent through the sensory nerve Th e amortization phase, the time on the to the spinal cord where motor nerves ground, is the most important part of are stimulated and the muscle that was a plyometric . It represents the stretched contracts. Th is is called the turn around time from landing to take myotatic or stretch refl ex. Th e most off and is crucial for power development. common example of this is the knee tap If the amortization phase is too long, examination that doctors perform dur- the stretch refl ex is lost and there is no ing an annual check-up. When tapping plyometric eff ect. the knee, the patellar tendon and quad- riceps muscle group is rapidly stretched. Th e take off is the concentric contrac- Th e quadriceps muscle group will react tion that follows the landing. During to this by contracting. An impulse is this phase the stored elastic energy is also sent to the antagonist muscle group used to increase jump height and explo- inhibiting its contraction. During jump- sive power. ing activities the rapid of the muscles on landing causes the spindles Getting Ready for Figure 1. Landing to be activated and thereby add to the Plyometrics Landing Surface power output. Th e spindles are sensitive Plyometrics are a very high intensity Plyometrics can be performed indoors to the rate of stretch, the more rapid the form of training, placing substantial or outdoors. Th e landing surface should stretch the greater the activation level of on the , , and con- be able to absorb some of the shock of the spindle. Since most natural move- nective tissue. While plyometrics can landing. Gymnastic or mats ments will involve the activation of both enhance an athlete’s speed, power, and are good indoor surfaces as are the the muscle spindle and the elastic com- performance, it also places them at a sprung wood fl oors found in many ponents of the muscle, they both play greater risk of injury than less intense studios. Outdoors, plyometrics a role in the increase in power output training methods. Prior to starting a are done on the grass or sand. Jumping following SSC movements. program there are several variables to on concrete or asphalt can lead to knee, consider so the training sessions are per- ankle, and problems, as such these Plyometric Sequence formed in a safe and eff ective manner. surfaces should be avoided. Plyometric exercises always follow the same specifi c sequence: Landing Strength • A landing phase As a general rule an athlete should not Having a good strength base is essen- • An amortization phase be jumping if they do not know how to tial for performing plyometrics safely • Take off land. A good landing involves the knees and eff ectively. Without good lower remaining aligned over the toes, the body and core strength, the amortiza- Th e landing phase starts as soon as the trunk inclined forward slightly, the head tion phase becomes too long and much muscles start to experience an eccentric up, and the back fl at (fi gure 1). When of the benefi t of the plyometric is lost. contraction. Th e rapid eccentric con- an athlete is learning to do plyometrics Over the years, the need to one traction serves to stretch the elastic com- for the fi rst time they should spend to two times body weight has been sug- ponent of the muscle and activate the the fi rst two to three weeks focused on gested as a requirement for plyometrics. stretch refl ex. A high level of eccentric landing and being able to move out of While this is a good guideline for some strength is needed during the landing a landing before moving on to more of the higher intensity drills, simple phase. Inadequate strength will result in intense drills. jumps in place and hops over very low a slow rate of stretch and less activation barriers can be used with most athletes of the stretch refl ex. as long as they have demonstrated the ability to land properly.

NSCA’s Performance Training Journal | www.nsca-lift.org/perform Vol. 6 No. 5 | Page 20 Introduction to Plyometrics: Plyometrics Converting Strength to Power

Injury History until you are comfortable and confi dent About the Author Th ose athletes with a history of lower with the technique of the exercise. Ed McNeely is a founding partner in body injury must be full rehabilitated StrengthPro Inc. A Las Vegas based sport and have medical clearance prior to Plyometrics should not be performed science and nutrition business. He has been starting a plyometric program. Th e pro- more than two to three times per week a consultant to 17 Canadian National gram should start with basic running unless you are alternating days of upper and professional sports teams. Ed is the and change of direction drills including and lower body plyometric drills. If you author of fi ve books; Th e Resistance Band cuts, corners, and rotations before mov- are just starting to incorporate them Workout Book, Power Plyometrics, One ing on to higher intensity hops, throws, into your current conditioning program, Hundred Strength Exercises, Training for and jumps. two sessions per week is adequate. , and Skillful Rowing, and has published over 100 articles on training Designing a Plyometrics Rest Between Sets and athlete conditioning covering top- Rest and recovery are crucial variables in Program Intensity ics such as strength training, plyometrics, a plyometric program. Rest refers to the making weight, assessing fi tness, speed and Intensity is a measure of how hard you time that is taken between each exercise power development, planning and peri- work, often compared to the maximum or set. Recovery refers to the amount of odization, and aerobic fi tness. amount that you can do. Intensity is a time that is needed before the workout ▲ factor in determining the overall stress can be repeated. a training sessions creates. As a technique, the speed of move- Th e amount of rest that is taken depends ment and power produced in each repe- upon the duration of work and the type tition of plyometric training determines of drill or exercise used varying from whether or not you will get a training zero to seven minutes between sets adaptation. All repetitions in a plyomet- or exercises. Table 2 summarizes the ric exercise are performed at maximum duration of work and rest periods for speed and power, anything less deceases a variety of work periods. In this table the stretch shortening response and ply- the work period refers to the period of ometric eff ect of the movement. continuous work and may not represent the total time for each set. In the case of Contacts Per Session single response drills, it is common to Plyometrics are recorded by the number take fi ve to ten seconds between repeti- of single foot contacts with the ground. tions to reset your body position, this For example 80 contacts would be four can make the total time for the set quite sets of 10 repetitions with a two-legged long even though the continuous work type movement or a total of 80 steps time is very short, usually less than one with lunges. Th e volumes listed second. in table 1 represent the total number of contacts per training session, not the number of contacts per exercise. Th is Sample Beginner Program table assumes that each movement is at Table 3 contains a sample lower body 100% eff ort. Plyometrics performed at program that is suitable for someone anything less than 100% do not get the starting plyometrics. It is assumed that benefi t associated with rapid elastic force landing technique and body control are production. However, new plyometrics both good and that a dynamic warm up drill should be performed at 70% – 80% is done prior to the workout.

NSCA’s Performance Training Journal | www.nsca-lift.org/perform Vol. 6 No. 5 | Page 21 Introduction to Plyometrics: Plyometrics Converting Strength to Power

Table 1. Foot or Hand Contacts per Session Level Low Intensity Med. Intensity High Intensity Beginner 80 60 40 Intermediate 100 80 60 Advanced 140 120 100

Table 2. Work and Rest Periods Work Time Rest between reps Rest between sets Rest between exercises < 1s 5 – 10 s 1 – 2 minutes None 1 – 3 seconds None 2 – 3 minutes None 4 – 15 seconds None 2 – 4 minutes None 15 – 30 seconds None 3 – 5 minutes 5 – 10 minutes

Table 3. Sample Beginner Lower Body Plyometrics Program Exercise Sets Reps Total Rest Between Rest Between Sets Contacts Jumps Single response vertical jumps 3 5 30 5s 3 minutes Hurdle Hops 3 4 24 No rest 3 minutes Box jumps onto box 3 4 24 5s 3 minutes Totals 9 78

NSCA’s Performance Training Journal | www.nsca-lift.org/perform Vol. 6 No. 5 | Page 22