Quick anatomy lesson that will change how you think about injuries.
When you tear a muscle fiber, blood rushes in. The area gets inflamed, satellite cells activate, and within a few weeks you’ve got new functional muscle tissue. Muscles are highly vascularized — they have a rich blood supply — which is why they heal relatively fast.
Tendons and ligaments are a different story entirely.
Connective tissue is hypovascular — it has very little blood flow compared to muscle. A 2015 review in the Journal of Musculoskeletal and Neuronal Interactions found that tendon blood supply decreases further with age, which is why rotator cuff tears, Achilles tendinopathy, and elbow tendinitis become more common past 35.
Less blood flow means:
Fewer nutrients and growth factors reaching the damaged area
Slower clearance of inflammatory waste products
Longer inflammatory phases (the “stuck” loop from Monday’s email)
Higher likelihood of scar tissue instead of functional tissue
This is why “just rest it” doesn’t work well for tendon injuries. Rest reduces the already-limited blood flow even further. The tendon doesn’t get what it needs to remodel.
What does work:
Progressive loading. Specifically, eccentric exercises — where the muscle lengthens under load — have the most evidence for stimulating tendon remodeling. The Alfredson protocol for Achilles tendinopathy is the classic example: heavy eccentric heel drops, done daily, for 12 weeks. It works because the mechanical stimulus tells the tenocytes (tendon cells) to lay down organized collagen.
This is also why peptides like BPC-157 are particularly interesting for tendon injuries. Remember from Tuesday — BPC-157 upregulates VEGF and promotes angiogenesis. It’s essentially addressing the core problem with tendon healing: not enough blood supply. You’re creating new blood vessels in an area that doesn’t have enough.
Combine eccentric loading (mechanical stimulus) with BPC-157 (angiogenesis + inflammation resolution) and collagen + vitamin C pre-rehab (raw materials), and you’re hitting the tendon repair problem from three angles simultaneously.
That’s not bro-science. That’s just matching the intervention to the biology.
Tomorrow I’m closing out the week with a roundup of real recovery protocols from people in our community — what they ran, how long, and what happened. Actual case studies, not theory.