Single Leg Jump Test: Protocol and Limb Symmetry

Almost all "default" jump tests are bilateral: both legs work together, which can hide significant imbalances between the dominant and non-dominant side. The Single Leg Jump Test solves this in a simple way: it's the unilateral version of a horizontal jump, allowing you to directly compare both legs.

What does this test measure?

It assesses power and jumping ability of a single leg, allowing you to calculate the Limb Symmetry Index (LSI). It's one of the most commonly used tests as a "first filter" in return-to-sport assessments after knee and ankle injuries, and also as a tool for detecting asymmetries in uninjured athletes.

Equipment needed

• Flat, non-slip surface
• Tape measure
• Marked starting line

Execution protocol

1. The subject stands on one leg behind the starting line, with the free leg bent and not touching the ground
2. Instruct them to perform a single forward jump for maximum distance, taking off and landing on the same leg
3. The landing must be controlled and stable (without the free leg touching the ground or losing balance) for at least 2 seconds
4. Measure the distance from the starting line to the point of heel contact on landing
5. Repeat with the other leg
6. Perform 2-3 valid attempts per leg and record the best result for each side

Common mistakes

• Counting an unstable landing or one supported by the opposite leg as valid
• Not alternating the order of legs, causing accumulated fatigue that affects the second leg tested
• Not calculating the symmetry index, only recording the absolute distance for each leg separately
• Jumping with excessive trunk swing to compensate for lack of power in the supporting leg

How to interpret the result

The key data point is the Limb Symmetry Index (LSI):

$$LSI (\%) = \frac{\text{Distance affected/non-dominant leg}}{\text{Distance healthy/dominant leg}} \times 100$$

LSI	Interpretation
≥ 90%	Adequate symmetry
80-90%	Moderate deficit, work on specific unilateral power
< 80%	Significant deficit, prioritize unilateral strength and power work before progressing

As a reference for absolute distance, in active uninjured adults the single leg jump typically reaches between 65% and 75% of the distance of a bilateral horizontal jump.

Relationship to other tests

The Single Leg Jump is the entry point of the unilateral jump test battery. It makes sense to progress toward:

• Triple Hop test — a three-consecutive-jump version, more demanding
• Single leg explosive strength test (Single Leg CMJ) — adds a vertical and countermovement component

Record and track progress

Asymmetries between legs aren't always obvious at first glance, and can change with training or after an injury. With Movalytics you can record the distance for each leg separately at every assessment, and the app automatically calculates the symmetry index, letting you see at a glance whether the asymmetry is decreasing, staying the same, or worsening over time.

Frequently asked questions

What's the difference between this test and the bilateral horizontal jump? The bilateral horizontal jump uses both legs at once, which can mask an asymmetry without it being noticeable. The single leg jump forces each leg to work independently, revealing differences that would otherwise go unnoticed. Is it necessary to do this test if there's no previous injury? It's not mandatory, but it's highly recommended as part of an initial assessment: many significant asymmetries appear in athletes with no injury history, simply due to repeated loading patterns. What should I do if I detect a significant asymmetry? Before progressing to more demanding tests (triple hop, unilateral vertical jumps), it's worth including specific unilateral strength and power work to reduce the difference between legs.