The Science Behind Vertical Jump: How Your Body Generates Explosive Power

Every time you jump, your body performs an incredibly complex chain of events in a fraction of a second. Muscles contract at precise timing intervals, tendons store and release elastic energy, and your nervous system coordinates the entire sequence faster than you can consciously think about it.

Understanding the science behind vertical jumping is more than academic curiosity. When you know how your body generates explosive power, you can train smarter, target weaknesses, and make better decisions about your programming. This article breaks down the key physiological and biomechanical mechanisms that determine how high you can jump.

The Biomechanics of a Vertical Jump

A vertical jump can be divided into four distinct phases, each contributing to the final result.

Phase 1: The Countermovement

Before you go up, you go down. This downward dip is called the countermovement, and it is far more important than most athletes realize. During the countermovement, you rapidly flex your hips, knees, and ankles, lowering your center of mass.

This serves two critical purposes:

Pre-stretching the muscles. As you dip down, the muscles responsible for jumping (primarily the quadriceps, glutes, and calves) are rapidly stretched under load. This pre-stretch stores elastic energy in both the muscles and their associated tendons, which can be released during the upward phase.

Activating the stretch reflex. The rapid stretching of your muscles triggers a neural response called the myotatic stretch reflex. This reflex causes the stretched muscles to contract more forcefully than they would from a static position. It is an involuntary response that adds significant force to your jump.

Research shows that a countermovement jump is typically 10 to 20 percent higher than a squat jump (where you start from a static crouched position with no countermovement). That difference comes entirely from the elastic energy and stretch reflex generated during the countermovement.

Phase 2: Amortization (The Transition)

The amortization phase is the brief moment between the end of the countermovement (when you stop going down) and the beginning of the upward push. This phase should be as short as possible.

Why does speed matter here? Because elastic energy stored in your muscles and tendons during the countermovement dissipates as heat if the transition takes too long. Studies show that ground contact times longer than approximately 0.25 seconds result in significant loss of stored elastic energy.

This is why “sticking” at the bottom of a jump kills your height. Athletes who transition quickly from the countermovement into the push-off phase preserve more elastic energy and jump higher.

Phase 3: Concentric Push-Off

This is the phase most people think of when they picture a jump. It is the explosive upward drive. During this phase, your muscles contract concentrically (shortening) to extend your hips, knees, and ankles, propelling your body upward.

The push-off happens in a specific sequence known as the proximal-to-distal pattern:

1. Hip extension (glutes and hamstrings) initiates the movement
2. Knee extension (quadriceps) follows immediately
3. Ankle plantarflexion (calves) provides the final push-off

This sequential activation is like cracking a whip, with each joint building on the momentum generated by the previous one. Disrupting this sequence, for example by extending the knees before fully engaging the hips, reduces jump height.

The arm swing also contributes during this phase. Research consistently shows that a coordinated arm swing adds 10 to 15 percent to vertical jump height. The arms generate upward momentum that is transferred to the body through the shoulders, effectively pulling you higher.

Phase 4: Flight and Landing

Once your feet leave the ground, physics takes over. Your center of mass follows a predictable parabolic trajectory determined entirely by your takeoff velocity and angle. You cannot change your jump height once airborne, no matter what it looks like on TV.

What elite athletes do in the air is manipulate their body position to make it appear they are hanging or floating. By tucking their legs, raising their arms, or changing their body orientation, they alter the position of their center of mass relative to their limbs. But the center of mass itself follows the same arc regardless.

The Muscular System: Your Jump Engine

Fast-Twitch vs. Slow-Twitch Muscle Fibers

Your muscles contain two primary types of fibers, and the ratio between them significantly influences your jumping potential.

Type I (slow-twitch) fibers are designed for endurance. They produce less force but can sustain activity for long periods. Marathon runners tend to have a high proportion of slow-twitch fibers.

Type II (fast-twitch) fibers are designed for power. They produce significantly more force but fatigue quickly. Sprinters and jumpers tend to have a higher proportion of fast-twitch fibers. Type II fibers are further divided into:

• Type IIa: Moderately fast, with some endurance capacity
• Type IIx: The fastest and most powerful, but they fatigue very rapidly

The proportion of fast-twitch to slow-twitch fibers is largely determined by genetics. However, training can influence fiber characteristics to some degree. Explosive training (plyometrics, heavy lifting, sprinting) can shift Type IIa fibers toward more explosive characteristics and improve the contractile properties of existing fast-twitch fibers.

This is one of the reasons plyometric training is so effective for vertical jump improvement. It specifically targets and develops fast-twitch muscle fibers.

The Key Muscles Involved in Jumping

Gluteus maximus. The largest and most powerful muscle in the human body. The glutes are the primary driver of hip extension, which research identifies as the most important joint action in vertical jumping. Studies show that hip extension contributes approximately 40 percent of total jump height.

Quadriceps. The four muscles on the front of your thigh are responsible for knee extension, which contributes roughly 25 to 30 percent of jump height. The vastus lateralis and rectus femoris are particularly important.

Hamstrings. Working in conjunction with the glutes, the hamstrings assist with hip extension and also play a role in stabilizing the knee during the countermovement.

Calves (gastrocnemius and soleus). The calf muscles handle the final plantarflexion of the ankle, contributing approximately 15 to 20 percent of jump height. The gastrocnemius is more important for jumping because it crosses both the knee and ankle joints and has a higher proportion of fast-twitch fibers.

Core muscles. Your abdominals, obliques, and lower back muscles transfer force from your lower body through your trunk. A weak core leaks energy during this transfer, reducing effective jump height.

The Nervous System: Your Body’s Wiring

Muscular strength is only part of the equation. Your nervous system determines how effectively you can use the muscle you have.

Motor Unit Recruitment

A motor unit consists of a single motor neuron and all the muscle fibers it controls. When you need to produce force, your nervous system recruits motor units according to the size principle: smaller motor units (controlling slow-twitch fibers) are recruited first, followed by larger motor units (controlling fast-twitch fibers) as force demands increase.

Untrained individuals often cannot fully recruit their larger, more powerful motor units. This is why beginners can see significant vertical jump improvements without any change in muscle size. Through training, the nervous system learns to recruit more motor units and to recruit the large, powerful ones more readily.

Rate Coding

Beyond simply recruiting motor units, the nervous system controls how rapidly each motor unit fires. Increasing the firing rate of motor units increases the force each unit produces. Explosive training, particularly plyometrics, improves rate coding, allowing your muscles to produce more force in less time.

Intermuscular Coordination

Jumping requires precise coordination between multiple muscle groups firing in the correct sequence. Training improves this coordination, allowing for smoother and more efficient force production. This is one reason why practicing the actual movement pattern of jumping (as opposed to only doing isolation exercises) is so important.

Tendon Elasticity: Your Built-In Springs

Tendons are not just passive connectors between muscles and bones. They are elastic structures that store and release energy, acting like biological springs.

The Achilles tendon is particularly important for jumping. During the countermovement, the Achilles tendon is stretched and stores elastic energy. During the push-off phase, this energy is released, adding to the force produced by the calf muscles. Research suggests that tendon elasticity can contribute up to 25 percent of the total energy in a jump.

Tendons adapt to training, but much more slowly than muscles. This is one reason why plyometric training programs are typically 8 to 12 weeks or longer. It takes time for tendons to develop the stiffness and elasticity that optimize energy storage and return.

Practical Applications: Training Smarter

Understanding the science allows you to train with purpose. Here is how the key scientific principles translate to practical training decisions:

Train the stretch-shortening cycle. Depth jumps and reactive plyometrics specifically target this mechanism. These exercises should be a cornerstone of your jump training program. See our plyometric exercise guide for specific exercises.

Build maximal strength. Greater muscle strength gives you a higher force output ceiling. Squats, deadlifts, and power cleans develop the raw strength that plyometrics then teach you to express explosively. Our guide on how to increase your vertical jump covers the best strength exercises.

Minimize amortization time. Practice transitioning from eccentric to concentric movement as quickly as possible. This applies to plyometrics and to the countermovement in your actual jump.

Train the arm swing. Given that it contributes 10 to 15 percent of jump height, deliberately practicing your arm swing is one of the easiest ways to gain free inches.

Allow adequate recovery. Neurological and tendon adaptations require recovery time. Overtraining impairs neural function and prevents the adaptations you are trying to create.

Fuel the process. Your muscles and nervous system require proper nutrition to train, recover, and adapt. Check out our vertical jump nutrition guide for detailed recommendations.

Conclusion

Vertical jumping is not a simple muscle contraction. It is a precisely coordinated event involving your nervous system, muscles, tendons, and biomechanical timing. The athletes who jump the highest are those who optimize all of these systems, not just one.

By training with an understanding of these principles, you can make more informed decisions about your programming and avoid the common mistake of only training one component while neglecting others.

If you want a program that applies these scientific principles in a structured, progressive format, check out our best vertical jump programs of 2026. The top programs are built on the same sports science covered in this article.