Stefan Holm Never Squatted Heavy or Jumped High Off Two Feet. His Tendon Stiffness Gave Him Record Vertical Velocity

Elite jumping isn’t just about raw muscle power.

According to jump training specialist John Evans, the secret to explosive vertical leap lies in transforming tendons into highly efficient springs that store and release energy with maximum efficiency.

In a detailed training breakdown, Evans explains how athletes can systematically develop tendon stiffness and elastic properties to dramatically improve their jumping performance.

The difference between good jumpers and elite athletes often comes down to one critical factor: how well they recycle energy from their approach.

Understanding Tendon Mechanics: From Waves to Springs

At a microscopic level, tendons consist of bundles of collagen fibers arranged in a naturally wavy pattern. When force is applied, these fibers straighten segment by segment, creating spring-like properties that store mechanical energy.

Evans describes this transformation process in practical terms.

If you guys have ever done isometrics and you push into something immovable or using a kettle bell isometric, if you’re at really low loads, it feels soft. But at high force, these align in parallel and all of the springs are turned on and the tendon functions very stiff.

This stiffness is essential for explosive movements. The stiffer and more responsive tendons become, the more efficiently they convert landing forces into upward propulsion.

The Three Regions of Tendon Loading

When force is plotted against tendon stretch, researchers observe a characteristic S-shaped curve with three distinct zones.

The toe region represents initial loading where slack is removed from wavy collagen fibers. Minimal force is required during this phase.

The linear region is where athletic magic happens. During this phase, tendons typically deform 6-8% while generating substantial force relative to lengthening. This is where energy storage and release occurs most efficiently.

The failure region represents the breaking point where collagen links rupture. While this sounds negative, controlled exposure to near-failure loads can actually signal beneficial tendon remodeling and strengthening.

Cross-Links: The Secret to Elastic Performance

Between collagen fibers exist molecular structures called cross-links. The density and orientation of these cross-links directly determine how spring-like tendons behave.

Athletes with more cross-links aligned in appropriate directions can store and release dramatically more energy during jumping movements. This is what separates merely athletic individuals from truly explosive performers.

Evans points to high jumper Stefan Holm as a prime example of tendon-driven athleticism.

If you look at all of his metrics across the board, he’s not insanely strong in squatting. He’s not insanely powerful in power cleans or power snatch. And if you look at a lot of his two-foot jumping, it is unimpressive. However, when you throw him into approach, he takes all of that energy from the approach and orients it vertically, which results in some of the highest vertical velocities of all time.

The Muscle-Tendon Unit: Motor Meets Spring

Optimal jumping performance requires coordination between two distinct systems working in harmony.

Muscles function as motors, generating force through motor neuron recruitment. Tendons act as springs, capturing kinetic energy during landing and releasing it during takeoff.

During approach and landing, tendons progress through their loading curve: removing slack, building energy storage in the linear region, then rapidly reversing that stored energy during pushoff. Athletes essentially borrow energy from their approach, bank it temporarily in tendon structures, then withdraw it with interest during explosive extension.

Nature provides excellent examples of this principle. Gazelles bounce across terrain with remarkable efficiency thanks to short muscles attached to extraordinarily long, stiff tendons packed with cross-links. Tigers, conversely, rely heavily on muscular power for explosive jumps from stationary positions.

Regional Differences Within Tendons

Research from Keith Barr reveals that tendons don’t function uniformly along their length.

Near the muscle attachment, tendons exhibit greater potential for adaptation and experience significant shear forces. This region requires some compliance to accommodate muscle stretch during energy storage.

Closer to bone attachments, tendons function with much greater stiffness. Optimal performance requires fine-tuning both regions to balance compliance near muscles with rigidity near bones.

Why Most Plyometrics Miss the Mark

Many athletes perform plyometric exercises that fail to properly challenge tendon elasticity. Movements with excessively long ground contact times shift energy production toward muscular effort rather than elastic rebound.

These moderate-intensity, longer-duration plyometrics exist in an ineffective middle ground—neither pure strength work nor true elastic training.

Verkoshansky’s Shock Training Revolution

Dr. Yuri Verkoshansky, considered the father of shock training, discovered that effective tendon training requires incredibly stiff, violent landings that trigger almost unconscious neuromuscular responses.

His depth jump protocols emphasized rapid eccentric-to-isometric-to-concentric transitions with minimal ground contact time. The goal wasn’t maximum jump height but rather optimal energy recycling efficiency.

When Verkoshansky was testing out depth jumps and shock training, he found that the landings had to be incredibly stiff and violent. He wanted an almost unconscious response to your legs hitting the ground.

Verkoshansky recommended relatively modest box heights of 24-30 inches. Excessively high boxes increase ground contact time, transforming elastic exercises into muscular efforts that defeat the training purpose.

Quality Over Quantity in Tendon Training

High-quality execution is non-negotiable for effective tendon adaptation. The nervous system must pre-tension muscles, recruit maximum motor units rapidly, and prepare for ground contact to fully exploit tendon properties.

Excessive volume degrades quality as ATP-CP energy systems deplete. When fatigue sets in, training shifts from tendon elasticity to muscular endurance—a completely different stimulus.

Evans emphasizes that athletes must avoid “absorbing” force during landings. Instead, the objective is recycling energy through stiff, reactive ground contacts.

Lessons from Sprinting Mechanics

Observing elite sprinters like Usain Bolt provides insight into optimal tendon function. During maximum velocity sprinting, legs remain remarkably straight at ground contact, with contact times around 80 milliseconds.

At these speeds, muscles function almost entirely isometrically—there simply isn’t time for complete eccentric-isometric-concentric cycles. Tendons handle the vast majority of energy storage and release.

This principle applies directly to jumping, particularly for athletes using running approaches. Success requires running fast, pushing off the penultimate step, repositioning airborne, then contacting the ground already prepared for immediate takeoff.

The Six-Week Tendon Development Protocol

Evans outlines a progressive system for systematically developing spring-like tendon properties over six weeks.

Weeks 1-2: Isometric Conditioning

Foundation work begins with isometric exercises targeting either Achilles or patellar tendons. These prepare connective tissue for intense loads ahead while promoting cross-link development.

• Perform isometric holds at approximately 70% effort
• Maintain tension for 30-45 seconds per set
• Complete 3-5 sets with one-minute rest intervals
• Repeat every six hours when possible (based on Keith Barr’s research on tendon adaptation rates)

Sustained tension over extended intervals allows cross-links to slide apart and loads to distribute throughout tendon structures.

Weeks 2-4: Heavy Slow Strength Training

After initial conditioning, athletes incorporate controlled tempo squatting to develop the complete stretch-shortening cycle while continuing tendon adaptation.

• Perform 4 sets of 6 repetitions
• Use 4-second eccentric (lowering) phase
• Pause 1 second at bottom position
• Execute 4-second concentric (lifting) phase

This phase serves dual purposes: increasing muscular capacity while teaching collagen fibers to handle force across all contraction types.

Weeks 3-4: Landing Drills

Athletes begin storing elastic energy through controlled landing exercises—typically stepping off 18-24 inch boxes.

• Execute 4 sets of 6 drops
• Take extended rest between sets
• Land with tall posture, stiff torso, and minimal leg give
• Allow energy to dissipate without rebounding (yet)

These drills expose tendons to rapid force spikes and significant deformation without requiring immediate energy release. This prepares tissues for the final progression.

Weeks 5-6: Shock Training and Depth Jumps

The protocol culminates with true shock training where all previous elements combine to potentiate elastic performance.

• Perform 1-2 sessions weekly
• Step (don’t jump) off boxes of appropriate height
• Minimize ground contact time
• Rebound as explosively as possible
• Warm up with several depth drops before working sets

Box height matters less than execution quality. If ground contact times increase significantly or rebound quality degrades, the box is too high.

Proper depth jumps train the nervous system to activate muscles preemptively, stiffen tendon structures before contact, then explode off the ground using primarily stored elastic energy rather than muscular contraction.

Beyond Basic Protocols

While this six-week framework provides solid foundation, Evans notes that comprehensive jump training requires additional elements including power development, accessory work, and individualized weakness assessment.

Analyzing jump mechanics and ground contact times reveals how efficiently individual athletes store and release energy. Technical coaching for Olympic lifts, squats, and jumping technique ensures all training components work synergistically.

The transformation from average jumper to elite athlete requires systematic tendon development over extended periods. Rushing the progression or skipping foundational phases invites injury and limits adaptation.

Athletes who methodically develop cross-link density, tendon stiffness, and neuromuscular coordination unlock performance levels impossible through muscular strength alone. The key is respecting biological adaptation timelines while progressively challenging elastic properties through intelligent training design.