The CMJ (counter movement jump) is one of the most widely used explosive-power tests in strength and conditioning: quick to set up, reliable, and low-cost. This article, part of the athlete tracking guide for sports coaches, details the full protocol and how to interpret the results.

What is the CMJ

The CMJ measures the height of a vertical jump performed after a quick knee bend (counter-movement), with no pause between the descent and the takeoff. This movement engages the muscle's stretch-shortening cycle, making it a reliable indicator of lower-body explosive force production (study).

The protocol

Equipment needed

A contact mat, a force platform, or a video-based timing app are all enough; a force platform remains the reference, but a contact mat gives a reliable measure for everyday gym use.

How the test goes

Hands on the hips (to isolate leg work), the athlete quickly bends their knees then immediately follows with a maximal vertical takeoff, with no pause at the bottom of the movement. Three attempts spaced a minute apart is usually enough; keep the best result.

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Interpreting the results

A single result has limited value : it's the comparison with the same athlete's previous results, under similar conditions, that tells you about real progress. There's no reliable universal norm across every sport and level: it's better to build your own benchmarks from tracking your athletes than to compare against a generic norm. See Which Physical Tests to Pick, by Sport to place the CMJ within a broader test battery, and Planning a Typical Training Week for folding these testing sessions into your planning.

Best practices

Running the test under comparable conditions each time (same warm-up, a rested athlete, same surface) makes the comparison more reliable. Testing after a tiring session throws off the result with no relation to a real loss of explosive quality. The same principle applies on the endurance side : see The Half-Cooper Test for an equivalent field test on the aerobic side.

Key takeaways

  • The CMJ measures vertical jump height through a counter-movement, with no pause at the bottom.
  • A contact mat or an app is enough for everyday use.
  • Comparing to the same athlete's previous results matters more than a generic norm.
  • Three attempts with recovery, under comparable conditions each time.
  • Avoid testing after a tiring session.

Frequently asked questions

Does the CMJ require expensive equipment?

No, a contact mat or a smartphone timing app is enough for everyday use; a force platform remains the lab reference.

How many attempts should you run?

Three attempts with a minute of recovery between each is usually enough, keeping the best result.

Are there reference norms?

No reliable universal norm across every sport: it's better to build your own benchmarks from tracking each athlete over time.

Does the CMJ suit every sport?

It's relevant wherever lower-body explosive power matters, which covers most sports, though it's less central for purely endurance-based qualities.

Can you test right after a session?

Not recommended : accumulated fatigue throws off the result, which no longer reflects the athlete's real explosive quality.