Power into Plyometrics: A Basic Introduction

(originally posted on November 6th 2013 on former page The Strength Student Blog)
plyometrics phases

Plyometrics are an extremely popular part of many peoples training programs but too often people are performing them without focus or reason. This blog will look at the basic types of plyometrics, why they should be performed and what they improve. While plyometrics are a fantastic way to develop power in any athlete, a good plyometric program will see jumps steadily progressed and done with correct form.

WHAT DO PLYOMETRICS DO?

Plyometrics work on a muscle function known as the stretch shortening cycle (SSC). Effectively “the stretch shortening cycle is a type of muscle function in which the muscle is stretched immediately before being contracted” (Comyns and Flanagan 2008). Movements that utilise the SSC (going from eccentric to concentric) have shown to have greater power output than those of just concentric movement or movements going from an isometric to concentric movement. The SSC can be seen in movements such as the sidestep of a rugby player, the jump for a high ball in GAA, rapid change of direction in tennis, the powerful jump of a hurdler or the quick footwork of a fighter. There are two types of SSC, slow and fast.

The Stretch Shortening Cycle
The Stretch Shortening Cycle

“A slow stretch SSC is one that shows a large displacement at the hips, knees and ankles and takes longer than 250ms, while a fast SSC will display minimal displacement at the hip, knees and ankle joints and take less than 250ms” (Schmidtbleicher, 1992).  To make that easier it can be divided like so:

SLOW SSC

  • Longer than 250ms ground contact time
  • Large movement at the joints
  • g. Box Jumps, Counter Movement Jumps, Vertical Jumps, Standing Long Jumps
  • g. (in sport) jumping for a high ball

FAST SSC

  • Less than 250ms ground contact time
  • Small movement at the joints
  • g. Ankle Hops, Hurdle Hops, Drop Jumps
  • g. (in Sport) side-step, reactive jump

Determining whether an athlete can utilise their slow and fast SSC can be done using some simple tests with the use of an electronic jump mat. Slow SSC is calculated using the following formula:

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The counter movement jump (CMJ) is performed with the hands placed (and kept) on the hips throughout. The following video gives more detail on the jump: http://www.youtube.com/watch?v=u_AyVPdUVAU

The technical points for the CMJ are as follows:

  • Stand with feet shoulder width apart
  • Hands are placed on the hip and remain there throughout
  • The athlete quickly and explosively squats down and jumps up as high as possible
  • There is no pause between eccentric and concentric movements
  • Hands remain ‘glued’ to the hips at all times
  • Legs are straight without kicking out to the back or front
  • The athlete lands initially with stiff legs and then flexes at the hips, knees and ankle to avoid injury

The squat jump (SJ) is a similar jump however performed without the counter movement.

The technical points for the SJ are as follows:

  • Stand with feet shoulder width apart
  • Hands placed on the hips and remain there throughout the jump
  • Squat down to parallel and hold
  • Without any eccentric movement the athlete explosively jumps as high as possible
  • The athlete lands initially with stiff legs and then flexes to avoid injury

Using the above formula the score should be >1, showing that the athlete can use their slow SSC.

The fast SSC is measured using the following formula:

Untitled.png2

The drop jump (DJ) is performed by the stepping off a box and immediately jumping straight up on contacting the ground. It can be seen in the following video: http://www.youtube.com/watch?v=MfwJEahLn9k

The technical points for the DJ are as follows:

  • The athlete stands tall on top of the box
  • The athlete steps off of the box without jumping
  • The legs are like ‘stiff springs’
  • On contacting the ground with both feet, the athlete jumps upwards as high as possible
  • Legs are like ‘stiff springs’ to ensure minimal displacement at the joints
  • “Jump high, jump fast”

Again the formula should result in a score >1, showing that the athlete can effectively utilise the fast SSC.

The Fast SSC exercises can also help to develop Reactive Strength Index (RSI), which Young (1995) describes as “an individuals ability to change from an eccentric to a concentric contraction and can be considered a quantitative measure of explosiveness”. The RSI is used to determine an athlete’s optimal height to step from during a drop jump. To do this an athlete must perform a number of drop jumps from varying heights on to a jump mat. The height at which the athlete achieves the best result is the optimal height for performing the exercise.

Untitled.png3

 

PUTTING IT ALL TOGETHER

Putting together a plyometric program should rely on developing a solid base, good technique and see steady progressions.

  • Begin with landing mechanics of the slow SSC movements, perfecting a strong quiet landing, in a flexed position with knees aligned over the toes and an upright torso.

    erin_sterns_elite_body_-day-2_plyometrics-and-legs_graphics_depth-jump
    Landing Mechanics
  • Progress easily from countermovement jumps, on to box jumps and standing long jumps, including double, alternate and single leg jumps
  • When a solid foundation has been built and the athlete can effectively and correctly utilise the slow SSC then process onto the fast SSC movements.

A good base to follow for this is the Comyns and Flanagan (2008) program:

6-9086215858

  • Begin with landing mechanics
  • In the ankle hops focus on the teaching points “legs like stiff springs” so as to prevent too much flexion at the joints and “the ground is a hot surface” so as to encourage the athlete to get off the ground as quickly as possible
  • Use cones and low hurdles before introducing higher obstacles to jump over. Ensure a quick ground contact time.

Of course not everyone has access to a jump mat so using your eye to gauge the jump performance can rely on the two coaching points mentioned above (legs like “stiff springs” and “the ground is a hot surface”). Encouraging the athlete to get off the ground as quickly as possible will help develop an improved ground contact time.

 

RECOMMENDATIONS

There are a number of recommendations available for people performing plyometrics varying from first being able to squat 1.5 x bodyweight even up to 1.8 x bodyweight before starting. While a good strength foundation is recommended, for the less experienced athlete simple jumps such as the countermovement jump or box jump may be included at a lower intensity focusing on technique and particularly landing mechanics to serve as an introduction. The following table shows an idea of the number of jumps/contacts a session should include

Table-1.-Contacts-per-session
(optimumh.co.uk)

The intensity of the jumps must also be considered, a drop jump can be considered high intensity while activities like a jump and hold is considered low intensity. For rest periods allow 5-10 seconds between reps and 2-3 minutes between sets. Baechle and Earle (2008) write, “The time between sets is determined by a proper work-to-rest ratio (i.e., 1:5 to 1:10) and is specific to the volume and type of drill being performed.” As plyometrics require a max power output and tax the central nervous system, fatigue must be accounted for so the same type of drills shouldn’t be done two days in a row. Allowing two days between sessions will help maintain a high standard of performance. 

WHEN TO DO IT

While elite athletes may have time to include sessions based solely around plyometrics in their program, most people do possess that luxury. An easy method of including plyometric work into a session is to include it in a weights training session after a suitable warm up and before heavy strength work. An example of a one-hour session may follow this pattern:

  • 15 minutes warm up and plyometrics
  • 45 minutes strength work

Complex training (a plyometric exercise preceded by a heavy strength exercise) to achieve a post activation potentiation (PAP) effect may also be used but requires a rest period between exercises that is largely individualized for optimum performance and may vary from 2 and even up to 8 minutes which renders this training mode less effective for most athletes who have a time constraint for their training. For this reason placing the plyometrics at the beginning of the session will serve the athlete better and elicit a similar training response.

 SUMMARY

Plyometric training sessions are a valuable asset for all athletes to include in their training program once done in an organised, progressive plan. When deciding to include plyometrics in a training plan remember the following points:

  • Plyometrics train both the slow and fast stretch shortening cycles (SSC)
  • Movements using the SSC produce more power than those without
  • Slow SSC movement have a ground contact time of >250ms
  • Fast SSC movements have a ground contact time of <250ms
  • A jump mat can be used to determine an athletes ability to utilise their SSC ability
  • Programs should see a slow and steady progression
  • Landing mechanics and technique should be perfected before intensity is risen
  • A good strength foundation should precede any plyometric work
  • Number of ground contacts/jumps and jump type will dictate the session intensity
  • Placing plyometrics at the start of a weights session, after a suitable warm up will allow for a time efficient training session

Ed.

 

References

  • Flanagan, E., Comyns, T. (2008) The Use of Contact Time and the Reactive Strength Index to Optimize Fast Stretch-Shortening Cycle Training. National Strength and Conditioning Association
  • How to Utilise Plyometric Training to Convert Strength into Power (2013) Optimum Health. Found at http://www.optimumh.co.uk/how-to-utilise-plyometric-training-to-convert-strength-into-power/
  • Schmidtbleicher, D., (1992(. Training for Power Events. Strength and Power in Sports, P.V. Komi, Ed., 381-395, Oxford: Blackwell
  • Baechle, T., Earle, R. (2008). Essentials of Strength training and Conditioning. National Strength and Conditioning Association. Human Kinetics; Champaign IL
  • Young, W., (1995). Laboratory Strength Assessment of Athletes. New Studies in Athletics, 10(1), 88-96.

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