Collagen for tendon recovery: the dose, the timing, and the vitamin C detail
Tendons are the tissue most endurance athletes only think about once they're already sore. Achilles, patellar, the anterior tibialis that starts complaining somewhere in a long training block. Muscle adapts in days. Tendon adapts in months, because it has poor blood supply and a slow collagen turnover rate.
Collagen for tendon recovery has a narrower evidence base than creatine, and a more interesting one, because the mechanism depends almost entirely on when you take it and what you take it with.
Why tendons are the slow tissue
Tendon is roughly 65 to 80 percent type I collagen by dry weight. It transmits force from muscle to bone, and it stiffens or weakens in response to loading over a timescale of weeks to months.
Blood supply is the constraint. Tendon is poorly vascularised compared with muscle, so delivering amino acids to the tissue is harder and repair is slower. This is why a strained hamstring settles in a fortnight while an angry Achilles hangs around for a season.
For a Hyrox athlete this shows up in specific places. The running volume loads the Achilles and the plantar fascia. The sled push loads the calf complex hard through a compressed range. Wall balls hammer the patellar tendon at depth, 100 times.
What the research actually shows
The study that changed the conversation came from Keith Baar's lab at UC Davis. Shaw and colleagues (2017) gave subjects gelatin enriched with vitamin C, then had them do 6 minutes of skipping an hour later. Blood markers of collagen synthesis roughly doubled in the group taking 15g compared with placebo.
Two details from that study matter more than the headline.
First, the collagen was taken before the loading, not after. The window was roughly 30 to 60 minutes ahead of the session, so amino acid availability peaked in the blood while the tendon was being loaded.
Second, vitamin C was in the mix. Vitamin C is a required cofactor for the enzymes that hydroxylate proline and lysine during collagen synthesis. Without it, the raw material sits there and the build stalls.
A 2021 systematic review in Amino Acids pooled the collagen peptide literature and found reasonable support for joint pain reduction and connective tissue outcomes, with the caveats you'd expect from a young field: small samples, varied protocols, mixed quality.
So the honest position is that the mechanism is sound, the acute synthesis data is good, and the long-term injury prevention data is still thin.
The protocol
Three things to get right.
Dose. 15g of collagen peptides or gelatin. Lower doses have been studied and 15g is where the acute synthesis response has been most consistently shown.
Timing. 30 to 60 minutes before loading the tendon. That means before your run, before your lifting session, before rehab work. Taking collagen at bedtime is a fine protein snack and a wasted opportunity for the tendon.
Vitamin C. 50mg or more alongside it. A piece of fruit covers this. So does most orange juice. If your collagen product doesn't include vitamin C, add it yourself rather than assume it doesn't matter.
Then load the tissue. Collagen supplies substrate. Mechanical loading is the signal that tells the tendon to build. Without the loading stimulus, you've had an expensive protein shake.
Where collagen sits against whey
They do different jobs, and the amino acid profile is the reason.
Whey is rich in leucine, which triggers muscle protein synthesis. Collagen is low in leucine and high in glycine, proline and hydroxyproline, which are the building blocks of connective tissue. Collagen is a poor choice for muscle building and whey is a poor choice for tendon substrate.
Most athletes running high volume need both. If you're only going to take one, take whey and treat collagen as the targeted addition when connective tissue is the limiter. Our protein timing guide covers the daily total.
Bovine, marine, and what's on the label
Bovine collagen is the most studied form and the most cost-effective. Marine collagen has smaller peptides and slightly faster absorption in some studies, and costs considerably more. Both deliver the same amino acids.
Look for hydrolysed collagen peptides rather than raw gelatin if you want something that dissolves in cold water. Gelatin works but needs warm liquid and sets as it cools.
Check the grams per serving. A product with a 5g scoop needs three scoops to reach the studied dose, which changes the price per serving substantially.
Interval's Bovine Collagen is 300g of unflavoured hydrolysed bovine collagen at £18.99. Unflavoured means it goes into a smoothie, coffee or juice without argument, and taking it with juice handles the vitamin C requirement at the same time.
Managing expectations
Tendon remodelling runs on a scale of months. A 2 week trial tells you nothing. If you're using collagen to address a grumbling Achilles, give it a full training block alongside progressive loading and expect gradual change.
Collagen won't fix a load management problem. If your mileage jumped 40 percent in a fortnight and your tendon is protesting, the answer is in your training log. Supplements support adaptation. They don't replace patience.
And it won't help acute inflammation in the first few days after an injury. That's a rest, load-modification and physiotherapy conversation.
The honest summary
15g of collagen peptides, with vitamin C, 30 to 60 minutes before you load the tendon. Then do the loading.
The acute synthesis evidence is genuinely good. The long-term injury data is still building. For an athlete putting 40km a week through the same Achilles while also doing wall balls, it's a reasonable low-risk addition to a recovery plan that already includes sleep and sensible load progression.
Those two are free, and they matter more.
Sources
- Shaw G, Lee-Barthel A, Ross ML, Wang B, Baar K. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr. 2017;105(1):136-143.
- Khatri M et al. The effects of collagen peptide supplementation on body composition, collagen synthesis, and recovery from joint injury and exercise: a systematic review. Amino Acids. 2021;53(10):1493-1506.