Achilles & Patellar Tendinopathy Rehab: Exercise Prescription Based on Tendon Strain
Spoiler alert: tendons aren’t passive ropes waiting to snap. They’re living tissues that respond (sometimes dramatically) to how you load them. Load too little and they weaken. Load too much and they break down. Get it just right—welcome to the Goldilocks zone of tendon rehab.
How Tendons Respond to Exercise (Mechanobiology Made Simple)
Tendons are more than connective tissue cables—they’re biologically active, constantly remodeling to match the demands you put on them. Inside, tenocytes monitor every stretch, compressive force, and shear stress. Through mechanotransduction (yes, that science-y word again), these cells turn physical forces into chemical signals that control collagen production and breakdown (Wang, 2006; Wang et al., 2015).
If you under-load the tendon, it gets the message “we’re not needed here” and starts reducing collagen synthesis. This leads to a weaker, more compliant tendon. Overload it, and the cells release enzymes that degrade collagen, causing microdamage, inflammation, and pain. But, when you apply the right level of strain, tenocytes increase collagen type I production, strengthen the extracellular matrix, and improve tendon stiffness and resilience (Bohm et al., 2015).
Early rehab strategy: This is why isometrics are often step one in rehab. Holding isometric calf contractions (straight knee or bent knee) or wall sits for the quads delivers safe, consistent loading that wakes up the tendon without pushing it into overload. These also help calm pain pathways, which is especially useful in the early flare-up stage of Achilles or patellar tendinopathy (Pollock et al., 2021).
The Goldilocks Zone: Strain Sweet Spot for Tendon Rehab
Research shows tendons thrive in a sweet spot: 4.5–6.5% strain. This is where adaptation occurs—stiffness increases, material properties improve, and tendons become better at handling everyday loads (Arampatzis et al., 2007; Bohm et al., 2023).
Why does this matter? Because once you creep into the ≥9% strain range, risk skyrockets. At this point, collagen fibrils start to fail at a microscopic level. Prospective studies on athletes have shown those with higher maximum strains had over 2x the risk of developing symptomatic tendinopathy compared to peers with lower strains (Mersmann et al., 2023).
Exercises to target the anabolic zone:
Standing and seated calf raises with heavy load (to hit ~5% strain).
Decline squats or leg press for patellar tendon loading.
Step-ups or weighted stair climbs as functional progressions.
In practice, this means working near 85–95% of your maximum voluntary contraction (MVC)—not “light toning” work, but controlled, heavy, tendon-specific loading.
Why Slow Loading Beats Bouncing
Not all load is created equal. Tendons adapt best when you load them slowly and deliberately. Tenocytes need sustained deformation to trigger anabolic responses—fast, bouncy movements like plyometrics don’t keep the tissue under strain long enough (Arampatzis et al., 2010).
This doesn’t mean plyos are useless (they’re great for muscle power), but if your goal is tendon rehab, slow and heavy wins the day. Studies comparing heavy slow resistance (HSR) training with fast contractions consistently show HSR improves tendon stiffness, while fast training often leaves tendons unchanged (Bohm et al., 2015).
Best exercises here:
Slow calf raises: 3s up, 3s down.
Slow single-leg squats or step-ups with controlled lowering.
Long-duration isometric holds (30s per rep) for both quads and calves.
This approach also helps reduce pain during loading—important for keeping people consistent and confident with their rehab.
Older Adults & Tendon Rehab in Canberra: Special Considerations
Ageing tendons are not doomed—but they do need a different game plan. By the time we hit our 60s, tendons have accumulated cross-links, become less hydrated, and adapt more slowly (Reeves et al., 2003). They’re also more compliant, meaning the same muscle contraction can create higher strain than in younger athletes.
This is where calibration matters. For older adults, jumping straight into “heavy” may overshoot into the danger zone. But go too light, and the tendon won’t adapt at all.
Evidence-based approach:
Start with isometric holds (30s calf or wall sits, 3–4 sets).
Progress to heavy slow calf raises (standing + seated), gradually adding load over weeks.
Include leg press or squats for patellar tendon, focusing on controlled movement.
Heavy load resistance training (versus moderate) has been shown to significantly increase patellar tendon stiffness in older adults (Eriksen et al., 2019). Similarly, 14 weeks of cyclic loading in women aged 60–75 improved Achilles stiffness and strength by over 20% (Reeves et al., 2003). In other words—yes, older tendons can remodel, they just take their time.
Practical Exercise Prescription: A Step-by-Step Plan
Here’s a framework you can use for tendinopathy rehab:
Weeks 0–2: Isometric Phase
Calf isometric holds (straight + bent knee), 30s, 3–4 sets, 2–3×/week.
Wall sits or quadriceps isometric holds, 30s, 3 sets.
👉 Purpose: reduce pain, start loading safely.
Weeks 3–8: Heavy Slow Resistance (HSR)
Calf raises (standing + seated), 4 sets of 5–8 reps, 3s down/3s up.
Decline single-leg squats or leg press, 3–4 sets of 6–10 reps.
👉 Purpose: stimulate tendon adaptation in the anabolic window.
Weeks 8–16+: Functional Loading
Step-ups, stair climbing, walking drills.
Introduce eccentric heel drops (modified Alfredson protocol) if tolerated.
Low-level plyometrics (skipping, hopping) once tendon is strong and pain-free.
👉 Purpose: restore sport or daily-life function, prepare tendon for higher demands.
Pain monitoring is crucial: up to 4/10 discomfort is considered acceptable during exercise, provided it settles within 24 hours. This ensures the tendon is being loaded without pushing it into tissue breakdown.
Take-Home Message
Forget cookie-cutter “3x10” prescriptions. Tendons need strain-smart training. Stay in the 4.5–6.5% strain window, respect slower adaptation in older adults, and focus on loading smarter, not heavier.
Load your tendons right, and they’ll reward you with strength, stiffness (the good kind), and a much lower risk of grumpy, painful breakdowns.
👉 Looking for Achilles tendinopathy rehab in Canberra or a safe tendon loading program for older adults? Book a session at The Body Lab—we’ll help your tendons find their happy place.
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