👉 Are tendons elastic? The truth about elasticity, performance and training

Yes, tendons are elastic, but not the way a rubber band is. They behave like biomechanical springs: under load they deform slightly, store energy and give it back into the drive. In the jump this mechanism is called the stretch-shortening cycle, and it's trainable.

If you train to improve your vertical jump, sooner or later you've asked this question. And the answer changes quite a lot about how you set your training up.

Here's how they actually work, why they matter in explosive movements, and the three concrete methods to train them.

What tendons are and what role they play in the jump

Tendons connect muscles to bones. They're tough structures, made mostly of collagen, designed to transmit the force the muscle produces.

In the jump, though, they don't just act as a transmission cable. They become an active part of the mechanism: they lengthen on the way down and shorten on the drive, giving back part of the energy. This behaviour is called viscoelastic, and it's why a well-trained movement comes out more explosive and less tiring for the same amount of muscular strength.

Are tendons elastic? Yes, but not like muscles

The key difference: muscles contract, tendons don't. Tendons deform under load and return to their original shape, releasing energy.

What happens during a jump

• Descent phase (pre-load). You bend the knees, the ankle flexes, the Achilles tendon and the patellar tendon stretch and store elastic energy.
• Transition. This is the critical moment: stay down too long and the stored energy dissipates as heat and you lose it.
• Takeoff phase. The tendon shortens and returns the energy, adding it to the muscular contraction.

The technical name for this sequence is the stretch-shortening cycle (SSC). It's why you jump higher with a countermovement than from a static squat position.

The detail almost nobody trains

The speed of the transition. You can have reactive tendons and waste them with a slow descent and a pause at the bottom. That's why serious training measures ground contact time, not just height.

Why tendon elasticity is crucial for the vertical jump

If you train to jump higher, you have to accept one thing: it isn't only a matter of muscular strength. An athlete can be very strong in the squat and jump poorly, because they can't express that strength in the extremely short window the jump allows.

• A more reactive tendon returns more energy.
• A stiffer tendon transfers force in less time, with less leakage.
• A well-trained tendon lets you jump the same or better at a lower metabolic cost, which counts in the third set.

In countermovement jumps a meaningful share of the mechanical work comes from the elastic energy stored in the tendons, and the Achilles tendon is one of the main players. I'm not giving you a percentage because in the literature it varies a lot depending on the measurement protocol, and a precise number wouldn't help you much.

What is clear is the concept: people who jump well have learned to use that spring. People who only do slow, heavy work often never trained it.

Can you train tendon elasticity? Yes

Tendons respond to training, but with different timelines and stimuli than muscle. They adapt more slowly, have less blood supply and ask for fast, controlled stimuli repeated over time more than enormous loads.

1. Plyometrics

Reactive jumps, drop jumps, bounces, skips. The goal isn't to jump as high as possible: it's to spend as little time on the ground as possible. Low volumes, high quality, full rests.

2. Controlled eccentric and isometric work

Slow descents under load, isometric holds at different angles, nordic curls, eccentric calf raises. This kind of work is what appears to influence the structural properties of the tendon most, and it's also the basis of tendinopathy rehab.

3. Ballistic and contrast training

Explosive movements with light load (jump squats, throws), or the pairing of a heavy load followed by an explosive movement, which is the principle of contrast training.

An honest note

The tendon adapts more slowly than the muscle. That gap is exactly what generates tendinitis: the muscle gets strong, the athlete loads more, and the tendon hasn't finished adapting yet. If you feel discomfort in the patellar tendon, don't add jumps: cut back and work on the structure first.

Before training the spring, measure where you are

All of this only makes sense if you have a reference. Otherwise, two months from now you won't be able to say whether the reactive work produced centimeters or just fatigue.

With the JHP jump test you upload a 2-second video and get the height in centimeters calculated from flight time. It's free and the video never leaves your device. The principle is always the same: measure first, then train, then measure again.

The JHP programs for reactivity and explosiveness

• JHP Contrast Method — contrast training, heavy load paired with an explosive movement. €90.
• Jumping Monster — 14 days of intensive plyometrics, 116 exercises. €40.
• JHP Vertical Upgrade — 36 sessions across 12 weeks. €67.
• Knee Power — knees and jumper's knee, the program to do before you raise your jump volumes. €40.

They're all included in the JHP subscription: 13 programs, WhatsApp support, €99 a year with free cancellation.

Frequently asked questions

Do tendons lengthen like muscles?

No. They deform slightly under load and return to their original shape. They don't contract and they don't gain length from stretching the way muscle tissue does.

How long does it take to see adaptations in tendons?

Longer than for muscle. It's months of work, not weeks, and it's the reason serious jump programs run 10-16 weeks and not 10 days.

Is plyometrics bad for your knees?

It's bad if volume grows too fast or if you start with an existing complaint. Done with progression and full rests, it's one of the best stimuli for making tendons more resilient.

In short

Tendons are elastic, but in the sense of biomechanical springs: you can make them stiffer, more reactive, more efficient. You can have strong legs, but if the spring isn't working your drive stays incomplete. Train strength, train reactivity, and measure the results in centimeters.

You might also like: How to increase your vertical jump with the French Contrast Method · Want to jump higher? Start here: 3 bodyweight exercises