The Stress-Adaptation Principle
The relationship between stress and tissue health follows a well-established principle: some stress is essential for adaptation, too much causes damage, and too little leads to atrophy. This concept, often called the “Goldilocks zone” of mechanical loading, underpins most rehabilitation approaches.
When a tendon is injured, the standard protocol typically begins with rest. When rest alone proves insufficient, progressive movement is reintroduced—because movement heals. It creates controlled mechanical stress that stimulates tissue repair and remodeling. For most injuries, this approach works.
But what happens when it doesn’t?
A Stubborn Case
I’ve experimented with stress-based healing for tendinopathies before, always with success. The approach was straightforward: gradually reintroduce movement along the longitudinal axis of the muscle and tendon—the direction of natural force transmission. Eccentric loading, stretching, progressive resistance. Textbook rehabilitation.
Then I developed a chronic Achilles tendinopathy that defied everything I tried. Rest, ice, anti-inflammatories, massage guns, dry needling, stretching—the usual arsenal. I even returned to running, which had paradoxically helped in the past. Nothing worked. The condition would improve but never fully resolve. After months of this cycle, I was stuck—and unwilling to pursue more invasive interventions like corticosteroid injections or platelet-rich plasma therapy.
An Observation from Combat Sports
The insight came unexpectedly. Watching fighters at a boxing camp, I noticed how they conditioned their shins, feet, and legs through repeated impact against heavy bags. These athletes subject their tissues to enormous compressive forces daily—yet they don’t suffer from chronic tendinopathies. Their connective tissues are remarkably resilient.
But here’s the key distinction: their conditioning doesn’t come from traditional gym training. They’re not strengthening tendons through longitudinal loading—the pulling and stretching forces we typically associate with resistance exercise. They’re conditioning through impact—vertical compression, perpendicular to the tendon’s long axis.
This triggered a memory. Years ago, when I practiced martial arts, I had a certain toughness that came not from lifting weights but from being thrown, from absorbing impact, from compressive forces applied in directions my gym training never addressed. I had been “gym strong” but also “martial arts tough.” Now I was only the former—and perhaps fragile in ways I hadn’t recognized.
The Experiment
The hypothesis was simple: what if compressive impact stress—perpendicular to the tendon’s axis—could stimulate a healing response that longitudinal loading couldn’t?
With nothing to lose, I began lightly but repetitively striking my Achilles tendon. Ten minutes daily, starting gently and progressively increasing intensity.
Within two weeks, the chronic pain that had persisted for months was gone.
Encouraged by this result, I expanded the practice to other tissues—hands, elbows, shoulders, knees, shins. After six months of consistent impact conditioning, the changes were unmistakable: I feel structurally tougher, I no longer have residual aches, and my Achilles can now absorb forces (like a spinning back kick against a heavy bag) that would have been unthinkable before. Estimated load tolerance has increased perhaps 10+-fold.
A Physiological Rationale
While I haven’t found extensive literature specifically on self-administered impact conditioning for tendinopathy, the underlying principle has scientific support.
Tendons are viscoelastic structures that adapt to mechanical demands through mechanotransduction—the process by which cells convert mechanical stimuli into biochemical signals that drive tissue remodeling. Importantly, tendons respond to the specific loading patterns they experience. A tendon trained only through longitudinal stress may lack the structural adaptations needed to handle compressive or shear forces.
Interestingly, this principle already has clinical application: extracorporeal shockwave therapy (ESWT) is an established treatment for chronic tendinopathies, particularly Achilles and patellar tendinopathies that resist conventional rehabilitation. Shockwave therapy delivers high-energy acoustic waves—essentially controlled compressive impacts—to stimulate neovascularization, collagen synthesis, and tissue repair. The mechanism appears to involve inducing controlled microtrauma that triggers regenerative cascades.
What I stumbled into empirically may share this mechanism: repetitive, low-to-moderate compressive stress creates a stimulus for adaptation that longitudinal loading alone cannot provide. The tendon is challenged in a different axis, prompting structural reinforcement in planes previously neglected.
Implications and Cautions
This is an n=1 observation, not a clinical trial. The approach carries obvious risks if applied too aggressively or to acute injuries. Tissue conditioning requires progressive overload and adequate recovery—the same principles that govern any training adaptation.
That said, the experience suggests a gap in how we typically approach tendon health. We train tendons to handle tension along their length, but we rarely condition them for impact or compression. For individuals whose tendinopathies resist conventional treatment, carefully introducing compressive stress might be worth exploring—ideally with professional guidance and an understanding that tissue adaptation takes time.
The fighters at that boxing camp weren’t doing anything revolutionary. They were applying a principle as old as martial arts itself: tissues adapt to the demands placed upon them. If you want to be tough, you have to train for toughness—in every axis.
Disclaimer: This post reflects personal experience and theoretical reasoning, not medical advice. Chronic tendinopathies should be evaluated by a qualified healthcare provider. Anyone considering impact conditioning should proceed gradually and be attentive to warning signs of tissue damage.
Martin Pham Dinh 