A Guide To Plyometrics - The 'How' And 'When' Of Plyometric Training by Colm Bourke

A Guide by Colm Bourke

Introduction

Plyometric exercises come in many different shapes and forms; each coach is tasked to think critically and juggle an array of variables to make suitable prescriptions based on factors such as environment, intent, and dosage relative to the athlete’s talent, sport, training history, injury profile, season timeline etc.

The purpose of this article is to provide coaches with different methods to execute plyometric movements with context and caveats to support decision making. Moreover, the emphasis will be placed on potentiation and principles for technical proficiency to better understand the ‘WHEN’ and ‘HOW’ behind the application of jump training.

The stretch-shortening cycle (SSC) is a spring like mechanism that occurs when a muscle lengthens and shortens; this sequence occurs in our everyday movements, but the rate of which it happens is based on activity and for convenience, classifying exercises as ‘fast’ or ‘slow’ depends on the length of the Ground Contact Time (GCT). Fast SSC <250ms, Slow SSC >250ms.

“Most of your plyometric work should be done just above, at, or below where the activity you want to improve sits on the force-velocity curve” – Dr. Joseph Coyne.

The direction or stance effects the specificity of the plyometric exercise; using rotational or lateral plyometric exercise will have a greater transference than a bilateral movement for field-based athletes.

Table 1 – Science for Sport (2016) Exercises and their GCT and the SSC classification

Post-Activation Potentiation (PAP)

Another useful way to integrate plyometric exercises is to fine-tune the central nervous system for activities that will occur later in the workout or the following day. Prescribing exercises that relate to the ‘theme’ of the workout can be a useful way to improve technical competence or physical readiness.

Table 2. Plyometrics and Potentiation

For a less trained athlete who has trouble projecting their body the Staggered Stance Broad Jump might be a suitable exercise, both from a learning and intensity perspective. Using a more dynamic exercise that emphasizes a ‘switching’ like motion might be more appropriate for athletes who are struggling to generate amplitude whilst sprinting.

Max-Velocity themed days often utilize shorter ground contacts so using exercises that touch on these components both in a manner of direction and GCT could help prepare the athlete. This also aligns with the principle I previously mentioned by Dr. Joseph Coyne, who has spent a great deal of time working with world class track and field sprinters and jumpers. Plyometrics that are performed pre-session are usually done with lower volumes compared to after the main component of the practice is completed.

Table 3. Plyometric Prescription Relative to Training Theme

World-class sprints coaches have shared how they utilize plyometric exercises like the straight leg bound and skip for distance before acceleration training to create a potentiation effect. Doing so may enable the athlete to apply force more efficiently or fine-tune the rhythm of the repetitions and thus increase performance over the desired distance (Turner et.al 2015). This application of the Post-activation Potentiation (PAP) method could be useful for athletes who struggle to achieve horizontal displacement.

Technical Proficiency

Regardless of whether the exercise is low or high intensity – executing sound technique is the key to performance and health.

-    Foot Contact

-    Postural Integrity

-    Synchronization

-    Stability

A high-level of competence in these domains is necessary for performance and injury-prevention – consistency and performance often go hand in hand. Establishing these principles early is essential, however it is important that over-cueing doesn’t impact the athlete’s proprioception or the ability to distinguish between well and poorly executed reps. Devising subtle interventions in the strength and conditioning program may play a role in improving posture and stability in less developed athletes. Remedial exercises like depth drops (no concentric movement) can help organize a lot of the above at a lower risk thus serving as a useful building block prior towards more reactive movements.

Synchronization of the joints and arm movements are common errors seen in less developed athletes. For example, holding the arms behind the body before performing a depth jump can help prepare for the arm punch used to generate height in the concentric portion of the exercise. During the eccentric portion of the movement, the hip, knee, and ankle should yield in congruence.

The foot should strike with a heel to toe roll or ‘full-foot’ contact for horizontal jumping. A full foot contact can provide a healthier balance of yielding across the three major joints. Although when GCT is the focus, a slightly more forefoot – with the ankle dorsiflexed may not be the preferred way to get the outcome you’re searching for. Forefoot landings place greater load on the Patella and Achilles tendon which increases the risk of overload but can elicit greater returns on tendon stiffness; coaches often integrate these modalities at peak periods of the year in small dosages. “Stiffness is calculated as the ratio of the applied force to the change in displacement of a body” Moran et.al 2021.

Using cues like “Don’t bend your knees” during plyometric training can be dangerous to underdeveloped athletes – especially when intensity and volume is high. If you are measuring an advanced athletes Reactive Strength Index (RSI), then using cues that focus on minimizing GCT is important, but practitioners must discern language associated with athlete’s competence and session goals. “Just because the athlete is able to initially perform the techniques perfectly, the clinician should not assume they have enough endurance to continue their flawless performance” Davies, Riemann, Manske (2015).

Note: This is partially why I have listed ranges of sets above vs concrete loading schemes.

We should attempt to look at the consistency of the reps as a whole vs one-off repetitions to guide our decision making. Here, a rating scale or wearable device like the one Output could be effective for monitoring ground contacts times in conjunction with what the coach is seeing from a postural standpoint. Overall, the goal should be high levels of technical competence paired with relative performance (GCT and Height).

Adaptation

Plyometric exercises are often prescribed at the beginning of micro or meso cycles to monitor levels of fatigue or adaptation – shown through an increase/decrease in power/reactivity. Tests like the Reactive Strength Index (RSI) account for how fast the athlete can move from eccentric to concentric and the amount of force produced within that sequence. The RSI is represented in the combination of jump height and contact time (Flanagan et al 2008).

Wearable devices like those offered at Output Sports can provide meaningful insights to assess if changes in reactive strength or power align with the theme of a training cycle. Devices like this serve as useful training agents to guide program design as the season progresses.

Alternatively, Track and Field coaches prescribe exercises like a standing triple jump to monitor training adaptation. The reactive strength component will provide similar indications about the athlete’s readiness. Another consideration is the execution of a standing triple jump, this movement tends to be more challenging than a repeated vertical jump, meaning there could be more variance between repetitions. It is also worth mentioning that horizontal activities like the standing triple jump are more hip dominant compared to their vertical counterparts which are more ankle dominant.

As training cycles develop and movement patterns become stable, practitioners usually progress the exercise selection to a more specific form that will elicit adaptation. In other words, coaches may begin with slow SSC movements to focus more on the mechanics like posture, foot placement, and stability. Some examples of this are in-place jump routines, isolating the eccentric component (depth drops), or low amplitude hopping.

Exercise selection influences the number of contacts that should be performed - to generate a training stimulus and avoid injury. For many coaches, stimulus exposure combined with proficient technique (potentially some leakage) can be a method for progression but there are caveats at play.

Table 4. (Adapted from the National Academy of Sports Medicine)

Traditional methods like extensive (high volume/low intensity) and intensive (low volume/high intensity) help categorize exercises into easy schemes - the first principles help guide our understanding of why this exercise is appropriate for this athlete. We should not assume that the exercise title classifies its intensity; a squat jump with 1/4 depth and the full range of motion are not the same.

The task constraints of the exercise can influence the Ground Reaction Forces (GRF) and Ground Contact Times (GCT) – for instance choosing a grass surface versus a track will influence ground contact time. The variety of factors at play give coaches the ability to select exercises to match the level and intensity they’re intending to prescribe. Factors like ‘Height of Fall’, ‘Speed’, ‘Stiffness’, and ‘Limb Loading’ are some mentioned by Sports Performance Practitioner Mike Young. Moreover, Table 4. Is a merely a guideline. Establishing safe parameters for high intensity drop jumps can be achieved by using a smaller box than their maximum CMJ and/or optimal drop height for RSI test.

The title of the exercise often reflects its intensity. Low-intensity versions of an exercise can develop the skill component of a sport at the early stages of pre-season e.g. a triple jumper bounding with less horizontal displacement on a softer surface may be used early in the preparatory phase. A bound is often classified as ‘Intense’ exercise, but ‘Baby Bounds’ is very rudimentary and can teach synchronization, postural awareness, and foot contacts.

Table 5. Sample Considerations for Plyometric Training Progression (Adapted from Jacob Jennings 2021)

Relating back to Mike’s example of ‘Limb Loading’ and ‘Height of Fall’, a bilateral exercise (double leg) is usually less intense than a unilateral exercise (single leg) due to the distribution of the load across two legs. However, if you took a conventional (two-legged) depth jump from a 90cm platform and compare it against a single leg depth jump off a (15cm). The higher drop height will likely be more intense because of the amortization on the joints at landings points and neurological output too.

Having a wide array of variables turns decision-making into a more challenging yet stimulating puzzle. We know that exposing athletes to high volumes and intensities with poor technique isn’t sustainable; I hope the information presented across this article gives starting points and tools/insights for continuous assessment of your plyometric training.

About The Author

Colm Bourke has 11 years competing as a Long Jumper. #1 Ranked Long Jumper in 2020 and 9th All-Time. He studied as Master's in Psychology at The University of Louisiana Monroe where he was a NCAA All Academic award recipient. Colm is now a Career Coach and Assistant Track and Field Coach at The University of Louisiana Monroe and the host of the Track and Field podcast.

References

Plyometrics and jump training, part 1: working back from the sport. (2021, October 19). Sportsmith. https://www.sportsmith.co/articles/plyometrics-and-jump-training-part-1-working-back-from-the-sport/

Turner, A. P., Bellhouse, S., Kilduff, L. P., & Russell, M. (2015). Postactivation Potentiation of Sprint Acceleration Performance Using Plyometric Exercise. Journal of Strength and Conditioning Research, 29(2), 343–350. https://doi.org/10.1519/jsc.0000000000000647

Davies, G., Riemann, B. L., & Manske, R. (2015). CURRENT CONCEPTS OF PLYOMETRIC EXERCISE. International journal of sports physical therapy, 10(6), 760–786.

Moran, J., Liew, B., Ramirez-Campillo, R., Granacher, U., Negra, Y., & Chaabene, H. (2021). The effects of plyometric jump training on lower-limb stiffness in healthy individuals: A meta-analytical comparison. Journal of Sport and Health Science. https://doi.org/10.1016/j.jshs.2021.05.005

Flanagan, E. P., & Comyns, T. M. (2008). The Use of Contact Time and the Reactive Strength Index to Optimize Fast Stretch-Shortening Cycle Training. Strength & Conditioning Journal, 30(5), 32–38. https://doi.org/10.1519/ssc.0b013e318187e25b

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