Collagen Peptides for Tendons: What the Evidence Shows

Collagen peptides are marketed for tendons, joints, skin, and athletic performance. The most useful question is not whether collagen is “good for connective tissue,” but which outcome changed, in whom, after what protocol, and whether the result matters to training or rehabilitation.

What the 2025 trial measured

A double-blind randomized trial assigned 50 healthy young sedentary men to 10 g of collagen peptides or placebo daily for 16 weeks. Researchers measured medial-gastrocnemius and Achilles-tendon stiffness, tissue cross-sectional area, maximal isometric plantar-flexion torque, and rate of torque development (Miyamoto et al.).

The collagen group increased muscle and tendon stiffness and normalized rate of torque development. The trial did not find significant changes in gastrocnemius or Achilles cross-sectional area, and maximal voluntary isometric torque did not improve significantly in either group. That means the result is about selected mechanical and explosive-force measures—not proof that collagen builds muscle or repairs an injured tendon.

The sample was small, young, sedentary, and male. The authors were affiliated with a collagen-product company, which does not invalidate the work but is relevant context when interpreting a single positive trial. It also means that a trained female lifter, an older adult, or somebody with tendinopathy is not represented by the study.

What broader evidence says

A 2024 systematic review and meta-analysis of 19 studies and 768 participants found statistically favourable results for several outcomes, including fat-free mass, tendon morphology, muscle architecture, maximal strength, and reactive-strength recovery. The authors rated certainty as moderate for body composition, very low for tendon morphology and mechanical properties, and low for several other outcomes (Bischof et al.).

That combination—positive pooled estimates with low or very low certainty for some connective-tissue outcomes—supports interest, not a guaranteed prescription. A separate 2024 study found that collagen peptide supplementation during one week of strenuous resistance exercise did not further increase connective-tissue protein-synthesis rates (Jäger et al.). Different measurements can therefore point in different directions.

What collagen is not

Collagen is an incomplete muscle-building protein because it is relatively low in essential amino acids and leucine. It should not displace complete dietary protein when the goal is supporting muscle protein accretion. Nor does a change in stiffness demonstrate that a tendon is “bulletproof,” that injury risk has fallen, or that a painful tendon has been treated.

Tendinopathy management generally depends on a graded loading plan, symptom monitoring, and sometimes clinical assessment. A collagen powder may be considered as an adjunct, but it cannot replace progressive rehabilitation or a diagnosis when pain, weakness, swelling, or loss of function persists.

How to interpret a product trial

The 2025 study used 10 g daily for 16 weeks, but that is a study protocol, not a universal dose. Commercial products vary in source, hydrolysis, serving size, testing, and added ingredients. There is not enough evidence to claim that 20 g, a particular collagen type, or a 30–60-minute pre-training window is the optimal routine for every lifter.

If you try it:

1. keep progressive training and adequate complete protein in place;
2. choose a product that states the actual collagen-peptide amount;
3. decide in advance which outcome you will track, such as pain/function under a clinician's plan or a repeatable explosive test;
4. change one variable at a time and stop if it causes intolerance or unnecessary expense.

Bottom line

Collagen peptides may influence selected connective-tissue, stiffness, recovery, or strength outcomes, but the certainty is mixed and the best direct 2025 trial did not show muscle or tendon enlargement. Treat collagen as an optional adjunct—not a muscle-building replacement, injury guarantee, or stand-alone tendon treatment.

Related reading

• Tendon training and the weak-link problem
• Training around injuries
• Protein and muscle growth

Limits of the evidence

Collagen studies differ in peptide product, dose, vitamin C co-ingestion, exercise, participant health, measurement method, and follow-up. Most do not establish return-to-sport, re-injury, or long-term clinical outcomes. Pain or loss of function deserves appropriate medical or physiotherapy assessment.

Sources

• Collagen peptide supplementation and muscle-tendon stiffness. 16-week randomized trial in 50 young sedentary men.
• Collagen peptides with long-term physical training. 2024 systematic review and meta-analysis; certainty varied by outcome.
• Collagen peptide supplementation during training and connective-tissue protein synthesis. 2024 controlled training study.
• The JUMPFOOD collagen and vitamin C tendinopathy protocol. Trial protocol; not evidence of clinical efficacy.