Natural Management

Evidence Review

Alfredson 1998 — The Original Eccentric Protocol

The foundational study in tendinopathy rehabilitation was a prospective pilot trial by Alfredson et al. in 15 recreational athletes (mean age 44) with chronic mid-portion Achilles tendinosis who had failed conventional treatment (NSAIDs, physiotherapy, orthotics) for at least 3 months [1]. Subjects performed heavy-load eccentric calf exercises — 3 sets of 15 reps twice daily, 7 days a week for 12 weeks — on both straight-knee and bent-knee positions to target both the gastrocnemius and soleus. Subjects were instructed to add load (using a backpack with weights) as pain allowed. All 15 patients returned to their pre-injury running level after 12 weeks. A comparison group of 15 matched athletes who chose conventional treatment did not improve and ultimately required surgery. While a small pilot without blinding, the study triggered two decades of research confirming the eccentric approach and its underlying mechanisms.

Beyer 2015 — Heavy Slow Resistance vs. Eccentric

Beyer and colleagues randomized 58 patients with chronic midportion Achilles tendinopathy to either the standard Alfredson eccentric protocol or heavy slow resistance training 3 times per week for 12 weeks, with follow-up at 52 weeks [2]. HSR involved heel raises, leg press, and squat exercises at 70–90% of 1-repetition maximum. The primary outcome was the VISA-A score (validated 0–100 score of Achilles tendon function) and VAS pain. At both 12 and 52 weeks, both groups showed large, significant improvements with no statistically significant difference between protocols. VISA-A improved by approximately 28 points in both groups at 52 weeks. Patient satisfaction at 12 weeks was numerically higher in the HSR group (67% fully satisfied vs. 57% for eccentric). Tendon neovascularization on Doppler ultrasound decreased similarly in both groups. The study established HSR as a legitimate first-line alternative to eccentric-only training, particularly for patients who find the twice-daily eccentric protocol difficult to adhere to.

Shaw 2017 — Collagen Synthesis Timing

Shaw and colleagues conducted a randomized crossover trial in 8 healthy recreationally active men testing whether consuming gelatin enriched with vitamin C before exercise could increase collagen synthesis [3]. Participants consumed either placebo, 5 g, or 15 g of vitamin C-enriched gelatin 60 minutes before a 6-minute rope-skipping session, with serum amino acid levels and collagen synthesis markers (PINP — procollagen I N-terminal propeptide) measured at intervals. The 15 g dose produced a two-fold increase in PINP at 4 hours post-exercise compared to placebo (p<0.05); the 5 g dose produced an intermediate effect. Serum glycine and proline — the primary amino acids in collagen — peaked approximately 60 minutes post-ingestion, aligning with the exercise window. The rope-skipping session alone increased PINP compared to rest, demonstrating that mechanical loading is required alongside the nutritional substrate. Limitations include the small sample size and healthy (non-tendinopathic) participants; however, the mechanistic findings informed subsequent clinical trials and have been widely adopted in tendon rehabilitation practice.

Praet 2019 — Collagen Peptides in Clinical Tendinopathy

Praet and colleagues conducted a pilot randomized crossover trial in 20 patients with chronic midportion Achilles tendinopathy, comparing specific bioactive collagen peptides (TENDOFORTE, 2.5 g/day) to placebo, both combined with a standardized bi-daily calf-strengthening and progressive return-to-running program over 6 months [4]. In a crossover design, Group AB (collagen first, then placebo) saw VISA-A improve by 12.6 points at 3 months, compared to 5.3 points in Group BA (placebo first). After crossover, groups converged, with Group BA improving by a further 17.7 points upon switching to collagen. The study was a pilot with a small sample and a crossover design that limits causal interpretation, but the effect size and direction consistently favored collagen supplementation, particularly in the early phase. Tendon vascularization assessed by Doppler ultrasound also improved numerically more in the collagen phase. The authors concluded that collagen peptides may accelerate the clinical benefits of structured loading exercise.

Millar 2021 — Comprehensive Disease Primer

Millar and colleagues produced a comprehensive review of tendinopathy pathophysiology and management across all major tendon sites, published in Nature Reviews Disease Primers [5]. The review describes the histopathological hallmarks of tendinopathy: disorganized collagen fibers, tenocyte apoptosis, increased matrix metalloproteinase activity, abnormal neovascularization with associated sensory nerve ingrowth, and dysregulated inflammatory signaling. Importantly, it distinguishes between reactive tendinopathy (acute, potentially reversible), tendon disrepair (incomplete healing), and degenerative tendinopathy (significant structural disorganization). The review confirms that progressive loading exercise remains the cornerstone of management across all stages, while noting that biological and nutritional interventions are gaining evidence as adjuncts. It identifies gaps in the evidence base including lack of adequately powered RCTs for most interventions and heterogeneity in patient populations, while affirming that surgery is appropriate only after 6–12 months of failed conservative management.