A systematic review published in March 2026 gives the clearest evidence yet on a question that's mattered to us since we built OOST: does collagen supplementation actually strengthen tendons, or is that more marketing than science? The review's own opening line could have come straight from our own positioning: tendons "transmit muscular forces to bone." That's not a coincidence — it's the actual biomechanics, and now there's a properly conducted systematic review putting numbers on it.
Quick Answer
A 2026 systematic review of eight randomised controlled trials found strong evidence (Grade A) that collagen supplementation increases tendon cross-sectional area and stiffness when combined with resistance training — but no additional effect on muscle strength beyond training alone. The strongest results came from higher doses (15–30g/day) with vitamin C, taken shortly before training.
What This Review Actually Did
Researchers from Stanford Health Care's Sports Medicine Rehabilitation Department searched four major databases through May 2025, screened 624 studies, and identified eight randomised controlled trials that met their criteria — all PEDro-scored as good-to-excellent quality. That's a genuinely rigorous process, not a marketing-friendly cherry-pick: the review followed PRISMA guidelines and was pre-registered before the analysis began.
What It Found — The Full Picture, Not Just the Good Parts
Strong evidence FOR tendon structural change
Three of four studies found significantly greater increases in tendon cross-sectional area in collagen-supplemented groups versus placebo. Four studies looked at tendon stiffness; the two using higher doses (15–30g/day) found significant between-group improvements, while lower-dose studies (~5g) only showed within-group change. The review rated this Grade A evidence — the strongest classification it uses.
Strong evidence AGAINST a muscle strength boost
This is the part that won't make it into most supplement marketing: across every study that measured it, resistance training improved muscle strength — but collagen supplementation added nothing on top of that. The review rated this Grade A evidence too, just in the other direction. Collagen isn't a strength supplement, and this review is honest about that.
Mixed evidence on muscle size and performance
Two studies found greater muscle hypertrophy with collagen, two found none. One study found improvements in eccentric force production during explosive movements; another found none. The review classifies this as Grade C — genuinely inconclusive, not a hidden win.
Why This Matters More for Rugby, GAA and Contact Sport Than It Sounds
It's easy to read "no effect on muscle strength" as disappointing. It isn't, if you understand what tendons actually do. Muscle generates force; tendons transmit it. A stronger, stiffer tendon doesn't make your muscles bigger — it makes the force your muscles already generate get delivered more efficiently into the tackle, the scrum, the sprint. That's a genuinely different (and for contact sport, arguably more relevant) benefit than muscle size, and it's exactly the mechanism this review found the strongest evidence for.
What the Dose and Timing Findings Mean for How You Take OOST
The review's strongest tendon results came from doses of 15–30g of collagen per day with vitamin C, and timing intake so amino acids are available in the bloodstream as training begins.
One sachet of OOST ReGen & Recover provides 8g of collagen — our standard daily protocol. If you're training at a higher volume, two sachets a day brings that to 16g, inside the range this review's strongest findings are based on, with no safety concern across the rest of the formula's ingredients at that level.
On timing: we've recommended 30–40 minutes before training since we built OOST, based on the foundational research (Shaw et al., 2017) showing collagen-building amino acids peak in the bloodstream in that window. This new review points to a similar window — refining the picture rather than changing it.
The Honest Limitations
This is early-stage evidence, and the review says so plainly: eight trials, 257 participants total, mostly young men aged 18–52, over relatively short interventions (3–15 weeks). It's a real, rigorously conducted systematic review — not a definitive final answer. More research on longer timeframes, older adults and women specifically is still needed, and the review's authors say so directly.
Frequently Asked Questions
Does this mean collagen doesn't help with muscle at all?
It means collagen doesn't add to muscle strength gains beyond what resistance training already produces. Its evidenced benefit is specifically in tendon structure and stiffness — a different, complementary mechanism to muscle-building.
Should I take two sachets of OOST instead of one?
One sachet remains the standard daily protocol. Two sachets (16g of collagen) is worth considering if you're training at a higher volume and want to be within the dose range this review's strongest tendon findings are based on.
Is 30–40 minutes still the right timing?
Yes — it sits within the window this and earlier foundational research both point to for amino acid availability ahead of mechanical loading.
Where can I read the actual study?
Buchalski A, Jeanfavre M, Altorelli C, Leff G. "Collagen Supplementation on Tendon-Related Structural and Performance Outcomes: A Systematic Review." Journal of Functional Morphology and Kinesiology, 2026;11(1):130 — published open access.
The Bottom Line
This is the clearest evidence to date that collagen supplementation genuinely changes tendon structure — not muscle size, tendon structure specifically — when paired with real training. For anyone whose sport depends on transmitting force through tendons and ligaments rather than just generating it, that's the mechanism that actually matters. See the full picture in our complete guide to collagen, or explore OOST ReGen & Recover.
Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. If you have any pre-existing medical conditions, are taking medication, or are pregnant or breastfeeding, consult your doctor before use.
