Single Leg Jump for RSI

An objective way to measure reactive strength and movement quality on each leg, independently of the other.

Table of Contents

• What is a Single Leg Jump for RSI Test?
• Test Instructions and Demonstration
• What do the Metrics Mean?

What is a single leg jump for RSI test?

Single Leg Jumps (SLJ) are a type of plyometric exercise involving consecutive jumps to measure the reactive strength index (RSI).

Plyometrics are exercises that enable a group of muscles to reach maximal strength as quickly as possible. They bridge the gap between speed and strength training  and provide an objective measure of power and movement quality. Additionally, SLJ testing can help to quantify lower-limb asymmetries as they assess each leg independently of the other.

In short, this test can be used to evaluate side-to-side differences in stretch-shortening cycle capacity in an individual's leg muscles. <- maybe define SSC before this

A practitioner can perform the SLJ RSI test to evaluate functional movement performance in:

1. Muscle strength and power reserves
2. Propulsive and absorptive strategies with foot-ground interactions
3. Degree of inter-limb asymmetry for all of the above components of movement performance

SLJ RSI test instructions:

Tip: Instruct the test subject that they should try to jump as high as they can and spend as little time on the ground as possible, like they're "hopping on a hot stove."

Start the Test

1. In plantiga.io, go to Record (left sidebar)
   1. From the Activity Type drop-down, select Single Leg Jump RSI
   2. From the Select People drop-down, select the athlete profile(s) being tested

Check for Warnings

2. It's important to resolve all warnings before starting, or data may not be recorded.
3. Click Start

Calibration

3. Instruct the athlete to stand still for 3 seconds at the start of the assessment

The Test

4. Once ready, cue the athlete to perform 5 consecutive jumps on each leg
   1. The athlete can choose which leg to start on

End the Test

5. Click Stop when finished
   1. (Optional) Add contextual notes
6. Choose one of the following:
   1. Done – finish and save
   2. Next – start another assessment
   3. Reset – discard the assessment

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What do the metrics mean?

Reactive Strength Index (RSI) asymmetry: a comparison of left vs. right stretch-shortening cycle capabilities during a SLJ RSI test.

Jump height asymmetry: a comparison of left vs. right max jump heights to indicate thigh muscle strength and power performance capabilities.

• When combined with single leg jump for height and distance testing, muscle asymmetry scores can identify trainable muscle deficits between the hip (glutes & hamstrings) vs. knee (quadriceps) to help improve overall movement symmetry and efficiency.

Push-off asymmetry: a comparison of the left vs. right side capacity to accelerate off the ground.

• High push-off asymmetry occurs when the opposite limb's quadriceps musculature and surrounding tissues are fatigued, weak or unable to produce the required strength/power/force to get off the ground for some reason. <- rework this

Impact asymmetry: a comparison of the ability of the left vs. right to absorb load when the foot lands between successive jumps.

• High impact asymmetry occurs when landing stiffer or more abruptly <- not the word I want to use here on one limb than the other.