Chronic Tendon Pain: Why Load Beats Rest, and What Shockwave Actually Does
Chronic Tendon Pain: Why Load Beats Rest, and What Shockwave Actually Does
By Dr. Rob Letizia, PT, DPT — Owner, Spectrum Therapeutics, Wayne, NJ
Every trainer has this client. Six weeks ago their Achilles started barking on the way up out of a heel raise. They backed off. It felt better. They came back, and by week two it hurt again — a little earlier, a little sharper. So they rested harder. Now it's month four, they've stopped running entirely, and the thing still hurts going down stairs.
Here's what nobody told them: the rest is why it still hurts.
That's not a slogan. It's the single most useful thing a trainer can understand about tendons, and it changes how you program for a client the moment you get it.
Tendinopathy is a capacity problem, not an inflammation problem
The old word was “tendinitis” — itis, inflammation. When researchers actually looked at chronic tendon tissue under a microscope, the classic inflammatory cells largely weren't there. What they found was a disorganized matrix: collagen fibers laid down in the wrong direction, extra ground substance, new blood vessels and nerve endings growing into tissue that should be relatively quiet. That's degeneration and failed healing, not a fire to put out. Hence the modern term, tendinopathy.
This matters for one practical reason. If the problem were inflammation, rest and ice would fix it. Since the problem is a tendon whose capacity has fallen below the demand being placed on it, there are only two levers: lower the demand, or raise the capacity.
Rest only pulls the first lever. And it pulls the second one backwards — tendon, like muscle, adapts to what you ask of it and detrains when you stop asking. So your client rests for six weeks, the pain quiets down because demand dropped to zero, and they return to a tendon that is now weaker than the one that got hurt. The pain comes back at a lower threshold than before. They interpret that as “I didn't rest long enough.”
That loop is the entire natural history of most chronic tendon pain I see in the clinic. Nobody in it is being lazy. They're following the wrong model.
The rule that replaces rest
You are not trying to avoid pain. You are trying to govern it.
The working standard — often called the pain-monitoring model — gives you three numbers:
1. Pain during the set stays at or below 5/10. Some discomfort is acceptable and does not mean damage.
2. Pain settles back to baseline within 24 hours. This is the one that matters most.
3. Pain is not worse from session to session across the week.
Hit all three and the load was appropriate, even if it hurt. Miss the 24-hour rule and the last session was too much — reduce the load by roughly 10–20% and rebuild, rather than stopping.
The reason to hand your client a rule instead of a pain threshold is that tendons are latent. They frequently feel fine during the session and complain the next morning. A client judging load by how it feels mid-set will chronically overshoot. Teach them to judge by tomorrow.
One more thing to set expectations on early: this is slow. Tendon remodels over months, not weeks. Twelve weeks of consistent loading is a normal timeline, and a client who quits at week five because it “isn't working” will conclude that loading failed when what actually failed was the dosing of their patience.
A four-stage progression you can actually run
None of the following requires special equipment, and all of it is squarely inside a trainer's scope for a client who has been cleared and has no red flags (see the referral section below). Progress a client to the next stage when they meet the criteria — not when the calendar says so.
Stage 1 — Isometrics: buy tolerance without losing load
Do this when: the tendon is highly irritable and even moderate loading blows past the 24-hour rule.
Isometrics let you put meaningful tension through the tendon without the lengthening-shortening cycle that tends to provoke it. For some clients they also take the edge off the pain for a few hours afterward, which buys you a window to train the rest of the body. That analgesic effect is real for some people and absent in others — the evidence is genuinely mixed. If two weeks of isometrics hasn't changed your client's pain, don't marry the stage. Move on.
Dose: 4–5 holds × 30–45 seconds, at roughly 70% of maximum effort, once or twice daily. Rest 1–2 minutes between holds.
· Achilles: double-leg heel-raise hold at mid-range, progressing toward single leg.
· Patellar: Spanish squat (band behind the knees, anchored in front) — knees at about 70–90°, torso upright.
· Gluteal / lateral hip: standing isometric abduction press into a wall, stance leg working.
· Lateral elbow: wrist extension hold against a fixed resistance, elbow slightly bent.
Wrist Pain: https://youtube.com/shorts/DwLRqNCTO3Q
Stage 2 — Heavy slow resistance: the actual treatment
Do this when: the client clears the 24-hour rule on isometrics.
This is the stage that changes the tendon, and it is the stage most trainers under-dose. Heavy slow resistance means genuinely heavy — you are progressing toward a 6–8 rep max by the end of the block — moved deliberately. The tempo is the point.
Dose: 3–4 sets × 6–15 reps, 3 seconds up and 3 seconds down, three times per week on non-consecutive days. Start around a 15RM and progress the load over 12 weeks toward a 6RM.
· Achilles: heel raises off a step through full available range, loaded with a barbell, dumbbells, or a weighted vest. Train straight-knee (gastroc) and bent-knee (soleus) versions. For insertional pain, start flat-footed rather than off a deficit.
· Patellar: leg press, squat, or Bulgarian split squat. Decline single-leg squat if you want more tendon load per unit of external weight.
· Gluteal / lateral hip: hip thrusts, loaded step-ups, side-lying or standing abduction. Keep the hip out of deep adduction early — crossing the legs, hanging on one hip, and sleeping with the top leg dropped forward all compress the tendon against bone and provoke it.
· Lateral elbow: heavy slow wrist extension, plus supination work with a hammer or an offset load.
The old eccentric-only protocols still work. So do concentric-eccentric heavy slow resistance and hybrid approaches. The literature keeps landing on the same conclusion: which loading protocol you choose matters far less than whether you load progressively and consistently. Pick the one your client will actually do three times a week.
Achilles Pain: https://youtube.com/shorts/yt4I3bMIy9Q
Stage 3 — Energy storage: reintroduce spring
Do this when: the client is strong and symptom-stable under heavy slow work, and their goal involves running, jumping, or cutting.
Heavy slow resistance builds a strong tendon. It does not build a tendon that tolerates rapid stretch-shorten cycles, and that's what fails when they go back to basketball. Reintroduce it deliberately: pogo hops, low-amplitude jump rope, skipping, then bounding — every other day, low volume, quality over quantity. Same 24-hour rule.
Knee Pain: https://youtube.com/shorts/u8dIEelT4U4
Stage 4 — Return to the actual demand
Rebuild toward the sport or the job, keeping two heavy slow sessions per week in the program indefinitely. Tendons detrain. If your client drops the strength work the day they feel normal, you'll see them again.
Five things I see trainers get wrong
1. Stretching the painful tendon. Compressive loading at end range provokes insertional tendinopathy specifically — Achilles at the heel, gluteal at the greater trochanter, hamstring at the sit bone. Aggressive stretching of an insertional problem often makes it worse.
2. Chasing today's pain. They deload every time a session stings, so the tendon never sees a progressive stimulus. Judge by tomorrow morning, not by the set.
3. Changing the exercise every week. Tendon adaptation needs repeated exposure to the same movement. Variety is the enemy here.
4. Deloading everything. A cranky Achilles is not a reason to stop training upper body, or the other leg, or anything else. Detraining the whole athlete to protect one tendon is a bad trade.
5. Ignoring what's upstream. Calf capacity for Achilles, glute and quad strength for patellar, hip abductor strength for gluteal tendinopathy. The tendon is often where the bill arrives, not where the debt was run up.
When to stop and refer — this part isn't optional
Progressive loading is appropriate for a client with an established, uncomplicated tendinopathy. Several things that look like tendon pain are not, and a few of them are time-sensitive. Refer out — same day for the first two — if you see:
· A sudden pop or snap with immediate loss of function. An inability to perform a single-leg heel raise is an Achilles rupture until a clinician proves otherwise.
· Numbness, tingling, radiating pain, or true weakness. That's a nerve conversation, not a tendon one.
· Pain at rest, or pain that wakes them at night, unrelated to how much they did that day.
· Redness, warmth, swelling, or fever.
· Several tendons flaring at once, or an hour-plus of morning stiffness in multiple joints — that pattern points toward a systemic or inflammatory cause.
· A recent course of fluoroquinolone antibiotics (ciprofloxacin, levofloxacin). These carry a known association with tendon injury and rupture. Ask the question; most clients won't volunteer it.
· A corticosteroid injection into the tendon in the last several weeks. Load management around that window is a clinical decision, not a training one.
· Unexplained weight loss, night sweats, or a history of cancer.
· Twelve weeks of well-executed, progressive loading with no meaningful change. Not an emergency — but it's a signal the working diagnosis deserves a second look.
In New Jersey and most states, a client can see a physical therapist directly without a physician referral, which makes “go get this looked at” a much lower-friction ask than trainers assume.
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What shockwave does — and what it doesn't
Extracorporeal shockwave therapy (ESWT) comes up constantly with tendon clients, usually via a podcast or a teammate, and it's worth knowing what it is before your client asks.
It's an in-clinic procedure: a handpiece delivers acoustic pressure waves into the tissue, a few minutes per area, no needles and no anesthetic, typically 3–5 sessions about a week apart. The proposed mechanism is mechanotransduction — a mechanical stimulus that nudges a stalled healing process back into gear.
Where the evidence is strongest: calcific rotator cuff tendinopathy and chronic plantar heel pain have the most consistent support, with reasonable evidence for insertional Achilles and greater trochanteric pain.
Where it's weaker: non-calcific tendinopathies and upper-limb cases generally, where the reviews don't show it clearly outperforming the alternatives. Study quality across the field is variable and the meta-analyses say so plainly.
Here's the part that matters for you, and the reason I'd rather your readers hear it from a PT than from an ad:
Shockwave does not build tendon capacity. Nothing does except load.
At its best it is an adjunct that reduces pain enough for a client to tolerate the loading program that is actually going to fix the problem. It is not a substitute for that program, and it is not a shortcut past it. Any clinic that offers it as a standalone treatment, without a progressive loading plan attached, is selling the wrong thing. The honest indication is a chronic case that has already failed six-plus weeks of well-executed loading — not a first-line option for a tendon that got cranky last week.
It's also not a trainer tool. It's a clinical procedure with real contraindications. What you can do is recognize the client who's a candidate — chronic, plateaued, loading properly and still stuck — and get them in front of someone who does it.
For transparency about my own bias: I offer shockwave in my clinic, so treat the above as a practitioner telling you where it fits rather than a neutral referee. Across the 23 shockwave (ESWT) patients of 2026 at my practice, a review of 17 patients who completed a course of shockwave therapy found 88% resolved or much improved (15 of 17). Not one of the 23 has required a cortisone injection or surgery. That is a small, single-clinic sample with no control group, and I'm giving you the N precisely because the N is the thing most people leave out.
The bottom line
Your client with the four-month Achilles doesn't need more rest. They need a tendon that can handle what they're asking of it, a rule for how hard to push, and about twelve weeks of patience.
Give them the 24-hour rule. Load them heavy and slow, three times a week, with the same handful of exercises. Watch for the referral signs. And if they're doing all of that properly and they're still stuck at week twelve, that's the moment a clinician earns their keep — not month one.
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Dr. Rob Letizia, PT, DPT is the owner of Spectrum Therapeutics in Wayne, New Jersey, a single-provider orthopedic clinic where every session is one-on-one with a doctor of physical therapy. He treats tendinopathy, post-surgical rehabilitation, and vestibular disorders, and offers on-site shockwave therapy for chronic tendon pain.
This article is general education for fitness professionals and is not medical advice or a substitute for individual evaluation. Trainers should work within their scope of practice and refer to a licensed clinician when the signs above are present.