Partly Substituting Whey for Collagen Peptide Supplementation Improves Neither Indices of Muscle Damage Nor Recovery of Functional Capacity During Eccentric Exercise Training in Fit Males.

One session of eccentric knee-extension exercise temporarily reduces knee strength by about 10% and increases a blood marker of muscle damage by 100% in healthy young men, but these changes return to normal after three weeks of continued training.

After three weeks of eccentric resistance training, levels of a specific bone and tendon marker called P1NP rise by about 10% in healthy young men. Taking collagen peptide supplements does not make this increase any larger.

Taking collagen peptides after intense exercise does not lead to greater muscle repair or higher levels of a specific collagen marker compared to taking whey protein alone in young men.

When fit young men do a specific type of leg exercise for three weeks, getting 45 grams of whey protein daily improves muscle strength, power, and recovery just as much as getting 25 grams of whey plus 20 grams of collagen peptides. This suggests that adding collagen peptides does not improve outcomes beyond what whey protein alone provides, as long as the total protein amount is the same.

In fit young men, performing eccentric resistance training for three weeks leads to an 8% increase in vertical jump height and a 10% increase in knee extension strength, whether or not their protein supplement contains collagen peptides.

Taking collagen supplements does not help muscles grow larger if you are already consuming enough total protein and vitamin C, because collagen does not contain the right amino acids or biological mechanism to directly stimulate muscle growth.