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1. Magnusson et al. (2010) – The Pathogenesis of Tendinopathy: Balancing the Response to Loading

1. Tendon tissue is metabolically active and adapts to both loading and unloading through collagen synthesis and degradation cycles.
2. Collagen synthesis peaks ~24 hours post-exercise and remains elevated for up to 72 hours, while collagen degradation peaks earlier—underscoring the need for recovery time.
3. Overloading can lead to pathological changes, such as disorganized collagen, increased proteoglycans, hypervascularity, and tenocyte rounding.
4. Tendinopathy does not feature classical inflammation but is marked by cellular apoptosis, increased MMPs, and altered ECM signaling.
5. Fibroblasts (tenocytes) act as mechanosensors in tendon remodeling and produce key ECM proteins in response to strain.
6. Too little or too much mechanical loading disrupts the balance of tendon remodeling and may initiate degenerative changes or fail to stimulate adaptation.

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2. Couppé et al. (2015) – Eccentric vs. Concentric Exercises in Tendinopathy

1. No strong evidence supports superiority of eccentric over concentric exercise for tendinopathy—benefits likely stem from mechanical load, not contraction type.
2. Tendon fibroblasts are strain-sensitive, with optimal collagen response observed between 3–5% strain (e.g. ~90% MVC loading).
3. Time under tension matters: slower, longer-duration loading (e.g. 6-second holds) leads to greater tendon adaptation than fast movements at equal volume.
4. Isometric loading may provide superior stiffness adaptation, potentially due to higher mechanical signal density per unit load.
5. Overloading can cause ECM microdamage, and insufficient rest between sessions may impair remodeling despite low metabolic demand.
6. Tendon hypertrophy is possible with both eccentric and concentric training if mechanical stimulus is sufficient—modality matters less than load structure.

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3. Wang et al. (2003) – Shockwave Therapy in Rabbit Tendons

1. Focused shockwave therapy stimulated neovascularization at the tendon–bone junction in rabbits, confirmed by histology and angiogenic markers.
2. Key molecules eNOS and VEGF increased at 1 week, peaked by week 4–8, and began returning to baseline by week 12.
3. PCNA (a cell proliferation marker) rose at 4 weeks and remained elevated through 12 weeks, indicating sustained regenerative activity.
4. Neovessel formation started around week 4 and was significantly greater than in controls—lasting through at least week 12.
5. Shockwaves induce biological effects in soft tissue, not only mechanical disruption—suggesting molecular healing pathways are activated.
6. Tendon regeneration is time-dependent, with the therapeutic window of biological remodeling following shockwave extending over 8–12 weeks
   

   Summary: 6 Core Principles

   1. Tendons are Slow Responders

   • Tendons have low cellular activity and blood supply.

   • Core collagen structure is laid down in adolescence and changes very little after age ~17.

   • Only a small outer layer of tendon adapts during adult loading — similar to tree rings.

   2. Loading is Essential – but Dose-Dependent

   • Moderate mechanical load increases collagen synthesis, growth factors (e.g. IGF-1, TGF-β), and enzymes like LOX (for collagen cross-linking).

   • However, there’s a sweet spot: too little = degradation; too much = microtrauma.

   • Isometric, concentric, and eccentric loads all stimulate tendon growth — intensity and time under tension matter more than contraction type.

   3. Unloading Rapidly Weakens Tendon

   • Immobilization or offloading leads to 80% decrease in collagen synthesis within 2–3 weeks.

   • Mechanical properties (stiffness, strength) decline before any visible atrophy.

   • Even adding growth hormone can only partially offset the effects of disuse.

   4. Ageing Reduces Plasticity

   • Age reduces tendon cell numbers and their ability to migrate, proliferate, or synthesize collagen.

   • But much of the decline is due to inactivity, not age per se.

   • Lifelong physical activity helps maintain tendon stiffness and reduces damaging cross-links like AGEs.

   5. Tendinopathy = Disorganized, Swollen, Stiff-but-Weak Tendon

   • Chronic tendon pain is linked to:

     • Disorganized collagen fibrils

     • Increased water, GAGs, and blood vessels

     • Rounder, more numerous fibroblasts

   • Loading-based rehab (eccentric, isometric, or heavy slow resistance) can remodel this structure — but very slowly.

   6. Healing is Incomplete and Prolonged After Injury

   • After rupture or surgery, tendons remain biologically active (e.g. high glucose uptake) for up to a year.

   • Stiffness recovers slowly over 6–12 months.

   • This prolonged activity suggests rehab must be long-term and progressive.Clinician Note — Helen’s Experience (11 Years in Shockwave)
     Over the past 11 years, Helen has used both focused and radial shockwave therapy on a wide range of tendon issues — from Achilles and patellar tendons to hamstrings and glutes. In our hands, combining targeted loading with shockwave stimulation accelerates tendon remodeling and creates a more robust recovery. While tricky tendons may take up to a year to fully regain strength, most see steady structural progress within six months when therapy is consistent and individualized.