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.

We analyzed the available evidence and found that after three weeks of eccentric resistance training, P1NP levels — a marker linked to bone and tendon remodeling — rise by about 10% in healthy young men [1]. We also looked at whether taking collagen peptide supplements boosts this effect, and found no additional increase when collagen was added [1]. The evidence we’ve reviewed so far includes one assertion that supports this pattern, with no studies contradicting it. This suggests that eccentric training, which involves lengthening muscles under load — like slowly lowering a weight — may stimulate biological activity related to connective tissue repair or growth in young men. However, adding collagen supplements did not appear to make that response stronger in the one case we examined. It’s important to note that this conclusion is based on a single assertion, and we don’t yet have data on how long these changes last, whether they occur in women or older adults, or if different doses or types of collagen might have different effects. We also don’t know if this 10% rise in P1NP translates to measurable changes in tendon strength or injury risk. What we’ve found so far is limited but consistent: eccentric training may raise P1NP, but collagen supplementation doesn’t seem to enhance that effect in the context of this one observation. More research is needed to understand the full picture. In everyday terms: if you’re a young man doing controlled, slow lowering movements in your workouts, your body may be responding in a way that supports tissue repair. But taking collagen pills alongside it doesn’t appear to make that response any bigger — at least not based on what we’ve seen so far.