Eccentric heel-drop protocol remodels degenerated Achilles collagen over 12 weeks.
Chronic overload leaves the Achilles tendon painful and structurally disorganized.
Chronic tendinopathy shows little inflammation, mostly collagen breakdown.
Repeated microtrauma outpaces the tendon's repair capacity.
Overuse degeneration replaces normal type I collagen with disorganized type III fibers.
Healthy collagen fibers align in tight parallel bundles.
Degenerated tendon fibers appear wavy, crimped, and scattered.
Morning stiffness and start-up pain mark early tendinopathy.
Pain often eases with activity, then returns afterward.
The Alfredson protocol prescribes eccentric heel drops twice daily.
Alfredson (1998) pioneered eccentric loading for chronic Achilles pain.
Patients lower slowly off a step, straight-legged and bent-knee.
Eccentric loading outperformed concentric exercise and surgery in early trials.
Lengthening contractions generate higher tendon force than shortening ones.
This mechanical stimulus drives adaptive collagen remodeling.
Some exercise pain is expected and considered acceptable.
Sharp or worsening pain signals the load is excessive.
Controlled microtrauma triggers tenocytes to synthesize fresh collagen.
Tendon cells sense mechanical strain through surface receptors.
Strain signals switch on collagen-producing gene expression.
Repeated eccentric strain converts tenocytes into active collagen-synthesizing cells.
New collagen deposition gradually favors organized type I fibers.
Type III collagen proportion falls as remodeling progresses.
Painful tendons often show abnormal neovascularization and nerve ingrowth.
Effective loading is linked to vessel regression and less pain.
Added external weight raises the tendon loading stimulus further.
Once pain allows, added weight increases loading demand.
Gradual overload keeps stimulating adaptation without re-injury.
Backpacks or weighted vests are added incrementally as symptoms allow.
Mechanical stiffness rises as collagen cross-links mature.
A stiffer tendon stores and returns energy more efficiently.
Pain should stay mild and settle within a day.
Persistent next-day pain signals load progressed too quickly.
By week twelve, organized collagen restores strength and function.
Collagen fibers now run in tight parallel alignment.
Tendon thickness and stiffness approach healthy baseline values.
Alfredson's original cohort returned to pre-injury activity within twelve weeks.
The VISA-A questionnaire scores pain, function, and activity level.
Higher scores reflect meaningful clinical improvement over the protocol.
Occasional maintenance loading helps preserve remodeled tendon structure.
Relapse risk rises if loading stops abruptly after recovery.