Learn all about the progressive assessment of jump assessment here.
In the world of athletic development, speed and jumping performance are often key qualities that determine performance. Plyometric exercises, which are based on the science of the stretch-shortening cycle, play a key role in improving athletic performance and serve as important criteria for returning to sports after injury. These exercises use the body's natural elastic properties to create explosive movements, offering a dynamic approach to training. A solid grasp of plyometrics enables professionals to design programs that significantly boost physical capabilities, leading to improved health and performance outcomes for athletes and individuals alike.
In this article, we will discuss how the use of smart force plates like AxIT Stomp-IT can be used to break down and understand the key elements of jumping.
- What assessments can be employed?
- Which metrics to scrutinize?
- Basic strategies for interventions.
Understanding the Stretch-Shortening Cycle (SSC)
The SSC is like the body's rubber band. It involves a three-step process where a musculotendinous unit is rapidly stretched, storing elastic energy as it reaches maximal length, and subsequently recoiling and shortening rapidly to generate an action such as jumping into the air.
For maximal elastic energy storage, this sequence must occur rapidly. Since only the initial and final phases involve movement, training emphasis revolves around enhancing both the eccentric and concentric components.
By breaking down these phases into appropriate Force Plate tests using Stomp-IT, practitioners can better determine where the focus is needed for the athletes they work with.
Eccentric Absorption
As described, the initial phase focuses on the eccentric component of movements, often referred to as the "force absorption" phase. This entails rapidly transitioning joints in the lower body from an extended to a flexed position. An example assessment and training exercise for eccentric absorption is the "tall-to-short" or "drop squat." This test can be created with a Custom Test variation of your standard squat assessment.
When evaluating results, metrics related to eccentric motions are key indicators. This phase sets the foundation for landing – much like learning to land before taking flight; this is an important first step.
The most important metric here is Peak Force. This is the maximum eccentric force generated throughout the movement; progression is indicated by increased peak force as the athlete becomes more adept at the action.
For athletes returning from injury, often the symmetry of the affected and unaffected limbs is most important. By establishing a target value, often around 10-15% asymmetry, clear criteria for advancement can be set.
Concentric Development
Concentric development targets the muscle-shortening facet of the jump and SSC. Immediately following the eccentric and energy storage phase of the jump, muscles rapidly contract as joints transition from flexion to extension. Concentric development is assessed using a Squat Jump test.
The Squat Jump assessment zeroes in on the concentric phase, which starts exactly where the drop squat assessment ends – at the bottom position of the squat. By pausing in this position before performing the jump action we remove the elastic effect of the SSC and allow AxIT to measure concentric force production.
Key metrics for concentric force development are:
- Jump Height: Peak vertical displacement post take-off, indicative of enhanced concentric power.
- Take Off Velocity: Maximal upward speed, improving this value indicates enhanced speed with increased power.
- RFD: Rate of force development during take-off; reflects acceleration capability and improves with targeted power-focused training.
Jump Phase
The Jump Phase combines the two movements tested above. It involves executing the eccentric and concentric components consecutively, marking the introduction of the stretch-shortening cycle. This stage, where the transition from tissue lengthening to shortening occurs during joint movement from flexion to extension, is assessed using the Countermovement Jump (CMJ).
CMJ metrics provide a comprehensive view of how athletes navigate jumping actions. Key metrics include:
- Jump Height: Reflecting improved SSC utilization and elastic properties as power increases.
- Eccentric Braking Impulse: Reflects proficiency in achieving greater momentum during eccentric phases.
- Concentric Propulsion Impulse: Modifying exercise tempo for greater momentum in the take off phase can enhance performance.
Repeat Jumps
Repeat jumps advance Jump Integration by introducing frequency. This involves consecutively performing bouts of the SSC. The 10/5 Repeat Jump/Hop Test evaluates this by observing performance changes over time, particularly as the athlete looks to optimize their efficiency in repeat jump performance.
Noteworthy metrics include:
- Reactive Strength Index (RSI): Average relationship between ground contact and Jump Height
- Ground Contact Time (GCT): Ground time between jumps, the shorter this time, typically the more elastic the jump. May help to indicate if this should be a training focus.
Drop Jump
Drop Jumps (DJ) intensify SSC stimulus by creating more eccentric load due to the drop-down height. This elevates force demand for transitioning from lengthening to shortening, rendering the plyometric action more challenging and making it a more advanced assessment of plyometric capacity and reactive strength.
Relevant metrics include:
- RSI: Ground-jump height relationship, progressing with SSC use, force production, and stiffness enhancement.
- Ground Contact Time: Time on the ground, driven by cues and the same training factors as Repeat Jump/Hop Tests.
- Jump Height: The ultimate reflection of jump performance.
Breaking down the details of plyometric exercises in the mentioned stages gives professionals a clear view of their clients' physical strengths and areas that need improvement. This understanding not only helps create personalized training plans but also sets a strong base for meeting specific criteria when working with athletes aiming for a successful comeback in sports. By using various tests, professionals can identify imbalances, find areas that need improvement, and recommend specific exercises to connect the gap between rehabilitation, a secure return to competition, and achieving top performance.