Collagen Peptides and Muscle-Tendon Stiffness: The 2025 Science

If you've been paying attention to sports nutrition research, you've probably seen collagen supplements touted for joint health. But a groundbreaking 2025 study published in Medicine & Science in Sports & Exercise suggests collagen might do much more—it could literally change how your muscles and tendons behave under load [1].

The Study: What They Found

Japanese researchers at Ritsumeikan University conducted a 16-week double-blind, randomized controlled trial with 50 healthy young sedentary males. Participants were divided into two groups:

• Collagen peptide (CP) group: 10g of collagen peptides daily
• Placebo group: Identical-looking beverage without collagen

Before and after the intervention, researchers measured:

• Muscle and tendon stiffness using ultrasound shear wave elastography
• Cross-sectional area of the medial gastrocnemius and Achilles tendon via MRI
• Maximal voluntary isometric contraction torque
• Rate of torque development (RTD)—a measure of explosive strength

The Results Were Clear

Muscle stiffness increased significantly in the collagen group (Cohen's d = 0.594), while the placebo group showed no change. Tendon stiffness increased significantly in the collagen group (Cohen's d = 0.378). Rate of torque development improved significantly in the collagen group (Cohen's d = 0.525), but not in the placebo group.

Notably, there were no significant changes in muscle or tendon cross-sectional area—meaning the benefits weren't from muscle growth, but from changes in tissue quality.

Here's the kicker: Researchers found a positive correlation between muscle stiffness and explosive strength. The stiffer the muscle, the more explosive the contraction [1].

Why This Matters for Lifters

Explosive Strength vs. Maximal Strength

Traditional strength training focuses on maximal force—you want to lift heavier weights. But many athletic movements require rapid force production: jumping, throwing, sprinting, or even the lockout on a deadlift.

Rate of torque development (RTD) measures how quickly you can generate force. Think of it as "power output" for your muscles. The 2025 study showed collagen specifically improved RTD without changing maximal strength [1].

This means collagen supplementation could benefit:

• Powerlifters needing faster lockouts
• Athletes in explosive sports (basketball, volleyball, track)
• Anyone wanting more "pop" in their movements

The Stiffness Connection

Here's the physiology: When your muscle-tendon unit is stiffer, less energy is "lost" during the stretch-shortening cycle. Your muscle can transmit force more efficiently to the bone, resulting in more explosive contractions [2].

Research from the Journal of Applied Physiology shows that muscle performance during maximal isometric and dynamic contractions is influenced by the stiffness of the tendinous structures [2]. Collagen appears to enhance this stiffness—without adding bulk.

Practical Implications

Dosage

The study used 10g of collagen peptides daily [1]. This aligns with previous research showing benefits at 15-30g daily, with 20g being a common recommendation for athletes [3].

Timing

While the study didn't specify optimal timing, previous research suggests taking collagen 30-60 minutes before training may enhance absorption when muscle protein synthesis is already elevated [3].

Type Matters

The research specifically used collagen peptides—hydrolyzed collagen that's been broken down into smaller, more absorbable peptides. Regular collagen powder won't dissolve as well and may not provide the same benefits.

Look for:

• Hydrolyzed collagen peptides
• Type I and III collagen (most abundant in skin and tendons)
• Third-party tested products

It's Not a Replacement

Let's be clear: Collagen supplementation won't build muscle mass the way creatine or sufficient protein will. It's an additive strategy—a way to optimize tissue quality rather than build tissue [1].

Think of it as another tool in your optimization toolkit:

• Protein: Builds muscle
• Creatine: Enhances performance and growth
• Collagen: Improves tissue stiffness and explosive capacity

The Bottom Line

The 2025 research is compelling: Daily collagen peptide supplementation increases both muscle and tendon stiffness, and this enhanced stiffness contributes to improved explosive strength [1].

For lifters and athletes whose performance depends on rapid force production—not just maximal strength—this could be a worthwhile addition to their supplement stack.

The key numbers:

• 10g daily for 16 weeks showed significant benefits
• ~20% improvement in rate of torque development
• No changes in muscle size—pure tissue quality optimization

If you're already hitting your protein goals and want that extra edge for explosive movements, collagen peptides deserve consideration.

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References

• Miyamoto N, et al. Collagen Peptide Supplementation Enhances Muscle-Tendon Stiffness and Explosive Strength: A 16-wk Randomized Controlled Trial. Med Sci Sports Exerc. 2025;57(12):2877-2886. PMID: 40623147.

• Bojsen-Møller J, Magnusson SP, Rasmussen LR, Kjaer M, Aagaard P. Muscle performance during maximal isometric and dynamic contractions is influenced by the stiffness of the tendinous structures. J Appl Physiol (1985). 2005;99(3):986-94.

• Kirmse M, et al. Impact of Collagen Peptide Supplementation in Combination with Long-Term Physical Training on Strength, Musculotendinous Remodeling, Functional Recovery, and Body Composition in Healthy Adults: A Systematic Review with Meta-analysis. Sports Med. 2024.