Plyometrics: getting back the bounce your tendons lost
Introduction
There's a physical quality that declines before strength and long before endurance, and that hardly anyone trains past a certain age: the ability to bounce.
A healthy tendon behaves like a spring. It stretches on impact, stores elastic energy and returns it in the next push-off. That mechanism — the stretch-shortening cycle — is what makes running more efficient than a series of isolated jumps, and what lets you recover your balance when you trip.
Plyometrics is the training of that quality. It has a reputation for being dangerous and reserved for young athletes. That reputation is half deserved: what's dangerous isn't jumping, it's jumping without having prepared the tissue to land.
Muscle adapts in weeks. Tendon adapts in months. Almost every plyometric injury lives in that gap.
What the stretch-shortening cycle is
When a muscle is stretched rapidly and contracts immediately afterward, it produces more force than contracting from a standstill. Two mechanisms are involved: elastic energy stored in the tendon and connective tissue, and a reflex response from the nervous system.
The key is timing. The interval between stretch and contraction has to be short; if you linger on the ground, elastic energy dissipates as heat and the spring effect disappears.
Hence the distinction between two types of work:
- Long cycle (ground contact over 250 milliseconds): jumps from a standstill, box jumps. More force, less elasticity.
- Short cycle (brief contact): jump rope, pogo hops, bounding. This is where tendon reactivity is trained.
What it's for beyond sport
Tendon health. Fast, cyclic loading is a specific stimulus that slow strength work doesn't fully reproduce. Tendons that never receive it become less tolerant of it, which explains why a single run hurts so much in someone who only walks.
Bone density. Moderate impact is one of the most effective stimuli for bone. A caveat here: in diagnosed osteoporosis, the type and dose of impact should be set by a professional.
Fall prevention. Recovering balance after a stumble requires producing force in fractions of a second. That's reactivity.
Running economy. A stiffer tendon — in the mechanical sense — returns more energy per stride.
A four-level progression
The rule that avoids nearly every problem: master the landing before chasing height.
Level 1: landings (2-3 weeks).
- Small vertical jumps landing softly and silently.
- Drops from a low step, landing and holding the position for 2 seconds.
- Goal: land silently, knees tracking over the feet, hips back. If it's loud, you're absorbing badly.
Level 2: extensive plyometrics (3-4 weeks).
- Jump rope: 3-5 sets of 30-45 seconds.
- Low, fast pogo hops on the spot: 3 sets of 15-20.
- Skipping and lateral movement.
- Low height, many contacts, none maximal.
Level 3: intensive plyometrics (from week 6-8).
- Box jumps: 4-5 sets of 4-6.
- Broad jumps with a controlled landing.
- Single-leg jumps, once both legs are solid.
- More height, fewer contacts, maximum quality.
Level 4: drop jumps (only on a solid base).
- Step off a low box (20-30 cm) and rebound immediately on contact.
- 3-4 sets of 4-5. It's the most demanding exercise for the tendon; height goes up very slowly.
How to dose it
Contacts. That's the volume unit: each landing counts as one. For beginners, 60-100 contacts per session of low-intensity work; for intensive work, 40-60 is enough.
Frequency. Two sessions a week, at least 48 hours apart.
Placement in the session. After the warm-up and before heavy work. Never at the end when tired: fatigue degrades landing technique, which is exactly where injuries happen.
Generous rests. 1-2 minutes between sets. This isn't metabolic conditioning.
Surface. Firm ground with some give: a wooden floor, grass, a track. Not bare concrete, and not a very soft mat, which kills the rebound and destabilizes the ankle.
Common mistakes
Starting with drop jumps. The most advanced exercise has become the most popular thanks to videos. It's the last item on the list, not the first.
Jumping down from the box. In box jumps you jump up and step down. Jumping down multiplies the load with no benefit.
Chasing height over quality. A high box usually means you're tucking your legs up a lot, not that you're jumping higher.
Doing it with accumulated fatigue. At the end of a session or on wrecked legs, risk spikes.
Too many contacts from day one. The tendon needs months. Enthusiasm lasts two weeks.
Ignoring Achilles or patellar discomfort. A tendon that complains is asking for less volume, not more effort.
When it isn't advisable, or needs precautions
Check first if you have: painful Achilles or patellar tendinopathy, osteoporosis or a history of fragility fracture, joint replacements, knee or hip problems, significant excess weight — impact scales with body weight — or recent lower-limb surgery.
For many of these there's a low-impact version: jumping in a pool, a mini-trampoline, or simply staying at level 1 for much longer.
Final thought
Plyometrics isn't an exercise for young athletes: it's how you remind a tendon that it still has to behave like a spring. And its great advantage is that the entry point costs nothing. Start with two weeks of silent landings and a jump rope three times a week. Once landing quietly is automatic, you'll have the base for everything else; until then, any big jump is a check written against an account with no funds.