The Countermovement Jump Test
The countermovement jump (CMJ) is an extremely well-documented test for evaluating lower-body power. Furthermore, it is widely considered as being the most reliable measure when compared to other jump tests. In the CMJ the athlete is tested in 3 key phases; braking (eccentric), propulsion (concentric) and landing, with each phase important and indicative of various sporting movements.
The Countermovement Jump Test – Step by Step
1. The Weighing Phase
The weighing phase is the period before the initiation of movement where the plates weigh the athlete. Therefore, it is essential for the athlete to remain as still as possible. The athlete should be standing upright with their hands on their hips. This phase is also referred to as the “Quiet” phase.
2. Unweighting Phase
After the signal to begin the test the athlete will start the countermovement by flexing at the knees and the hips to lower the body towards the ground. The force on the plates is reduced from the initial weighing phase. Therefore we are “unweighting”. This phase begins as soon as the athlete begins the movement; this is why it is crucial that the athlete remains still during the weighing phase.
3. Braking Phase
The braking phase is also known as the “stretching” and/or “eccentric” phase. As the athlete approaches there desired squat depth, they will begin to slow the centre of mass down by reapplying force. This ultimately acts to stop the bodies falling motion before moving into the propulsive phase. In our software, braking is defined as when an athlete’s Centre of Mass velocity is still negative but is ascending toward 0 m/s.
4. Propulsive Phase
After the athlete has stopped moving downwards, the propulsive phase begins. This phase is sometimes referred to as the “concentric” or “push-off” phase. In this phase, the athlete will rapidly extend their hips, knees and ankles to propel the body vertically which results in the Jump. By definition, this phase begins when the Centre of Mass velocity becomes positive and ends as soon as the athlete has left the plate.
5. Flight Phase
The Flight Phase begins once the athlete has entirely left the force plate, also known as the instant of take-off. This phase then ends at the instant of touchdown whereby the athlete first re-contacts the plate.
6. Landing Phase
The Landing Phase begins when the athlete re-connects to the plate from the jump. This phase requires the athlete to absorb the forces of the landing by flexing the hips, knees and ankles (not doing this will result in higher landing forces) with the goal of coming to complete stop in the shortest time possible.
Viewing and Analysing the Test Results
Who should be using this test?
Any sport that requires a measure of lower body power as it includes concentric and eccentric phases. The test can be combined with the squat test to evaluate an athletes eccentric utilisation ratio or combined with a mid-thigh pull to assess their dynamic strength index
Which metrics are recorded?
Over 40 metrics are automatically calculated. Some of the more commonly used metrics include; jump height, average forces, peak forces, the rate of force development, velocity, power, impulse, symmetry, time to stabilisation and reactive strength index.
How long does the test take?
4-6 seconds. This includes all phases from weighing to landing.
Where do I learn more?
Call us on 01344 623 883 for further information.