Collagen for athletes: what the trials show for joints, tendons and muscle

Collagen has moved from the beauty aisle to the gym bag, and the claims have grown with it. Some hold up: there are decent trials in athletes and active adults on joint discomfort, tendon recovery and, with resistance training, muscle. Some don't: collagen is not a muscle-building protein on its own, and it doesn't replace whey. Here's what the trials actually found, with doses, so you can decide whether it belongs in your routine.

What collagen is, for an athlete

Collagen is the main structural protein in tendons, ligaments, cartilage and bone, and about a third of all the protein in your body. A collagen supplement is that protein hydrolysed into short peptides that absorb easily. It's high in glycine, proline and hydroxyproline, the amino acids connective tissue is built from, and low in leucine, the amino acid that switches on muscle protein synthesis. That one fact explains most of what follows.

What the trials found

Joint discomfort in athletes. The best-known trial gave 147 college athletes with activity-related joint pain 10g of collagen hydrolysate or placebo daily for 24 weeks. The collagen group reported less pain at rest, walking, standing and carrying. A later German trial in 139 active adults used 5g a day of specific collagen peptides for 12 weeks and found less knee discomfort during activity than placebo. A Dutch trial at 10g in older active adults found no difference from placebo. So: a real but modest effect in 2 of 3 trials, at 5g to 10g, over 12 to 24 weeks.

Tendons. In a 6-month trial, 20 athletes with Achilles tendinopathy did a standard eccentric-loading rehab programme with either 2.5g of specific collagen peptides or placebo. The collagen group improved faster on the standard symptom score and returned to running sooner. It's a small trial, but it's the right design.

Collagen synthesis around training. A 2017 study at the Australian Institute of Sport gave young men 15g of gelatin with vitamin C an hour before 6 minutes of skipping, and measured markers of collagen synthesis in their blood. The markers roughly doubled compared with placebo, and engineered ligaments grown in the lab from their blood were stronger. That's the origin of the "collagen plus vitamin C before training" advice. It's a mechanism study, not an injury trial, so treat it as promising rather than proven.

Muscle. A 12-week trial in 53 older men combined 15g of specific collagen peptides a day with resistance training 3 times a week. The collagen group gained more lean mass and more strength than the placebo group doing the same training. Important detail: everyone trained. Collagen on its own didn't build anything in any trial.

What it won't do

• Replace whey or a protein target. Collagen is low in leucine and contains no tryptophan, so it isn't a complete protein and doesn't drive muscle protein synthesis the way whey or a meal does. Count it toward your protein total, but don't let it crowd out complete proteins.
• Act as an anti-inflammatory. Trials that measured inflammation markers found no change. The joint benefit appears to come from supporting cartilage, not from damping inflammation. More in Does collagen reduce inflammation?
• Prevent injury. Plausible from the synthesis studies, but no trial has yet shown fewer injuries in people taking collagen.

A practical protocol

The vitamin C is cheap insurance: about 50mg, which is an orange or a small glass of juice. Your body needs it to build collagen, and the synthesis study used it.

Collagen vs whey: not either/or

Whey (or any complete protein) builds muscle. Collagen supports the connective tissue that muscle pulls on. Many athletes take both: whey after training for muscle, collagen before training for tendons and joints. If you can only afford 1 and your goal is muscle, buy the complete protein. If your goal is joints or a tendon that keeps flaring, buy the collagen.

Frequently asked questions

Can I mix collagen into my whey shake?
Yes. It's tasteless and dissolves cold. That's the easiest way to take both.

Is Type II collagen better for joints?
Different product. Undenatured Type II is taken in tiny doses (40mg) and works through the immune system; the trials above used Type I/III hydrolysed collagen at gram doses. Both have evidence; don't mix up the doses.

Will it help running knees?
Activity-related knee discomfort is exactly what the 5g and 10g trials measured, and 2 of 3 found a benefit after 12 weeks or more. It's worth a proper 12-week trial on yourself. More in Collagen for joint health.

Is it allowed in tested sport?
Collagen is a food protein, not a banned substance. As with any supplement, buy from a source that tests for contaminants.

The studies

• Clark KL et al. (2008). 24-week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. Current Medical Research and Opinion 24:1485–1496. View →
• Zdzieblik D et al. (2017). Improvement of activity-related knee joint discomfort following supplementation of specific collagen peptides. Applied Physiology, Nutrition, and Metabolism 42:588–595. View →
• Bongers CCWG et al. (2020). Effectiveness of collagen supplementation on pain scores in healthy individuals with self-reported knee pain. Applied Physiology, Nutrition, and Metabolism 45:793–800. View →
• Praet SFE et al. (2019). Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in Achilles tendinopathy patients. Nutrients 11:76. Read it free →
• Shaw G et al. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. American Journal of Clinical Nutrition 105:136–143. Read it free →
• Zdzieblik D et al. (2015). Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men. British Journal of Nutrition 114:1237–1245. Read it free →

This article is general information, not medical advice. If you have an injury, see a physiotherapist or doctor; a supplement is not a rehab programme.

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