The Countermovement Rebound Test
The CMJ Rebound Test is a measure of an athlete’s reactive ability. This is similar to the drop jump; however, instead of dropping from an elevated surface, the athlete is falling from a previous countermovement jump. We typically incorporate this test to assess the fast stretch-shortening which is ideal for any sporting movements that occur in under 250ms. It is also excellent for speeding up the testing process as its effectively two jumps in one.
The Countermovement Rebound (CMRB) Test
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 fully 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. Rebound Braking Phase
This 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; this will slow the centre of mass down before transitioning into the propulsive phase
7. Rebound Propulsive Phase
After the rebound braking phase the athlete will begin to rapidly extend his hips, knees and ankles again to send the centre of mass upwards and into the 2nd jump (rebound jump)
8. Rebound Flight Phase
As before, this phase begins once the athlete has fully left the force plate and ends when they contact the plate again.
9. Rebound Landing Phase
The Landing Phase begins when the athlete re-connects to the plate from the rebound 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.
The Test Results
Who should do the test?
As a “2 tests in 1” movement, this is ideal for a complete evaluation of lower body power, tendon elasticity and reactivity. Any sport that requires both slow (over 250ms) and fast (under 250ms) movements should use this to help direct which type of movement their athlete needs to improve.
What metrics are recorded?
Over 30 metrics between the initial jump and the rebound jump. Some of the most popular metrics are jump heights, rebound contact time, time to stabilisation, reactive strength index, landing stiffness and peak forces through the phases.
How long does the test take?
5-7 seconds. This includes all phases from weighing through to the rebound landing.
Where do I learn more?
Please call 01344 623 883 for further information.