Counter-movement Jump (CMJ)

The Counter-movement Jump (CMJ) is a vertical jump performed with a preparatory downward movement prior to take-off (the "counter-movement"). It begins with a quick eccentric/pre-stretch phase (rapid squat-like descent and arm backswing), followed by a brief amortization phase (transition), and ends with a forceful concentric phase (upward jump). This jump pattern utilizes the stretch-shortening cycle (SSC) to enhance power output by optimizing elastic energy storage, stretch reflex activation, and neuromuscular coordination.

The CMJ is widely used in sports performance testing to assess lower-body power and rate of force development (RFD) . It is often contrasted with the squat jump (which begins from a static position) to evaluate an athlete’s ability to use the SSC effectively.

• Related Topics: Power , Plyometric Exercise , Stretch-shortening Cycle , Force-velocity Curve , Amortization Phase , Rate of Force Development , Counter-movement Jump (CMJ)

Related Courses:

• Power (High-velocity) Training: Introduction
• Lower Body Power Exercises
• Upper Body Power Exercises and Total Body Power Exercises

Frequently Asked Questions (FAQ):

What is the purpose of the counter-movement in a CMJ?

• The counter-movement enhances jump height by using the stretch-shortening cycle. The pre-stretch results in stored elastic energy in tendons and muscles, and activates the stretch reflex, both of which contribute to a more powerful concentric contraction.

How is the CMJ different from a squat jump?

• A squat jump begins from a static position without a prior descent, eliminating the stretch-shortening cycle. The CMJ includes a dynamic pre-load (eccentric phase), which typically results in higher jump heights and greater peak power output.

What does the CMJ test measure?

• The CMJ is primarily used to assess explosive lower-body power and, indirectly, neuromuscular readiness, fatigue, or asymmetries. It is a common performance metric in strength and conditioning, rehabilitation, and sports science.

What are the phases of the counter-movement jump?

1. Eccentric Phase: Rapid descent and arm backswing
2. Amortization Phase: Shortest possible pause at the botto
3. Concentric Phase: Explosive upward jump

Can CMJ performance be improved with training

• Yes. CMJ height and power can be improved with technique refinement, plyometric drills, and heavy strength training that focuses on overcoming the amortization phase and maximum velocity concentrics.

Why is the CMJ used in athlete monitoring?

• The CMJ is sensitive to fatigue and changes in neuromuscular performance. Tracking jump height, peak force, or ground contact time over time can help coaches assess training effectiveness, recovery status, or risk of injury.