What is a vertical countermovement jump (CMJ)?

The Countermovement Jump (CMJ) is a vertical jump test that involves a downward movement (countermovement) before an upward leap. This differentiates it from a squat jump, where the athlete starts from a stationary squat position. The CMJ harnesses the stretch-shortening cycle (SSC) for maximal force, unlike a squat jump's static start.

The CMJ involves starting upright, quickly lowering the center of mass by flexing hips, knees, and ankles (the eccentric phase), then immediately extending to jump vertically (the concentric phase). This sequence utilizes the SSC, where muscles and tendons store elastic energy during the downward movement and release it during the upward phase. It is a simple, practical, valid, and very reliable measure of lower-body power, and a foundational test utilised to assess an athlete's explosive power.

What is a vertical countermovement jump (CMJ)?

A vertical countermovement jump (CMJ) is a vertical jump that involves a downward movement (countermovement) before an upward leap. Moreover, the countermovement jump (CMJ) offers valuable insights into an athlete's explosive strength, neuromuscular efficiency and overall functional capacity. In addition, the countermovement jump (CMJ) is a very reliable measure of lower-body power, and it has become one of the most frequently used tests by coaches and researchers.

The countermovement jump (CMJ) is a vertical jump that involves a downward movement before an upward leap. The countermovement jump is a vertical jump test performed by having an athlete quickly squat to a self-selected depth and then jump as high as possible. So, you have a simple, practical, valid, and very reliable measure of lower-body power.

The CMJ is primarily used to measure an athlete's explosive lower-body power, and the CMJ has become one of the most frequently used tests by coaches and researchers to indirectly measure power in the lower limbs. As a consequence, it is no surprise this has become a cornerstone test for many strength and conditioning coaches and sports scientists, and arguably the most popular neuromuscular and physical performance test in the world.

What is the difference between a vertical jump and a CMJ?

The differences between a vertical jump and a CMJ are given in the table below.

aspect	vertical jump	CMJ
type	jump	jump
movement	arms free	arms fixed
start	stand	squat
countermovement	yes	yes
arm swing	yes	no
height	higher	lower
height difference	7 cm (2.76 inches)	7 cm (2.76 inches)
arm boost	18.9% to 38%	0%
tool	wall	plate
measure	reach	force
cost	low	high
use	field	lab
check	power	strength
check	explosiveness	spring
check	fitness	fatigue
check	sport position	coordination
reliability	medium	high
overestimation	5.5 inches (13.97 centimeters)	no

A vertical jump and a CMJ are vertical jump tests. The standing vertical jump lets moving your arms. The CMJ protocol limits arms swinging by needing hands on hips. So, the CMJ removes arm movement, which is why it checks leg strength and leg muscle capability without arm swing. The vertical jump test matches with maximum power and how fast you can run. The CMJ assesses leap height and checks how hard you push.

The CMJ has a countermovement before the jump. That's when you do a squat and then jump upward. This countermovement uses the stretch-shortening cycle, thanks to potentiation of parts that squeeze and pull. Because of this, a countermovement jump results in taller compared to a non-countermovement jump. However, swinging your arms makes you jump higher. Arm swing boosts peak force and raises center of speed. So, a standing vertical jump with moving your arms gives a higher jump height than a CMJ without moving your arms. In fact, jump height with swinging arms is roughly 50 centimeters (19.7 inches), while CMJ height without moving your arms is about 42 and a half centimeters (16.7 inches).

For measuring, the standing vertical jump uses apparatus for height, like a wall with chalk on fingers, or a vertical apparatus with fins. You measure the difference between standing reach and jumping reach. The CMJ protocol finds height from ground force measurements. It uses a force plate or pressure pad, which records vertical impulse and figures out hop height. That's why the CMJ needs costly tools and specialized practice, but it has accuracy for monitoring. The vertical jump test is hardwareonly and is not impractical for on-site checks.