Tendons serve many important roles in the human body’s ability to move. As dense, fibrous bands of connective tissue that attach muscles to bones, tendons transmit muscular forces to bone, absorb load, and allow the body to execute the many explosive movements that athletic bodies demand when participating in running and any form of hybrid training. Collagen supplementation has emerged as a promising adjunct to mechanical loading (resistance training) for promoting tendon remodeling. In this article, we examine how supplemental collagen can enhance recovery from tendon-related injuries.
The Link Between Tendons and Collagen
In addition to the mobility-related advantages mentioned above, tendons also provide a matrix for joint stability and serve as sources of elastic energy storage during dynamic tasks. Predominantly composed of Type I collagen, tendons adapt structurally and functionally to mechanical loading through increases in cross-sectional area as well as extracellular matrix organization. Collectively, these attributes enhance force transmission efficiency and injury resilience.
Tendons, however, do not function the same as muscles. In fact, for all of their abilities and accolades, tendons regularly work against some very basic disadvantages from a biological viewpoint:
- Poor blood supply: slows the delivery of nutrients and oxygen to tendon tissue
- Slow rate of cellular turnover: tendon cells regenerate far more slowly than muscle cells
- High collagen dependency: collagen comprises roughly 65 to 80% of tendons’ dry weight, making its quality and availability critical
- Limited healing capacity: once injured, tendons often form inferior scar tissue rather than achieving true regeneration
When tendon pathology occurs, whether it presents itself as a partial tear, patellar tendinopathy or Achilles tendinopathy, the origin almost always defaults to a disruption to the collagen matrix. The tendon tissue gets “disorganized,” so to speak; the collagen cross-links degrade, and the structure loses stiffness/mechanical integrity. Armed with this knowledge, scientists have asked whether collagen supplementation can provide the raw material needed to support rebuilding that matrix during rehabilitation.
Collagen and Strength Training
Although collagen supplementation has undergone extensive investigation for its effects on joint pain and cartilage health, research has now moved toward exploring its potential role in enhancing tendon and muscle adaptation when combined with resistance training. Studies consistently demonstrate that collagen ingestion, when timed around mechanical loading, can stimulate collagen synthesis and may improve tissue mechanical properties. However, findings from trials remain mixed: while some report improvements in tendon cross-sectional area and stiffness, others show minimal effects on muscle strength, hypertrophy, or performance. This inconsistency highlights the lack of clearly defined evidence-based guidelines regarding optimal collagen supplementation protocols, in both clinical rehabilitation and athletic performance settings.
A systematic review conducted in 2025 found strong evidence against collagen supplementation having any meaningful effect on muscle strength. The reason for this lies within its structural. Muscle hypertrophy and force production come about largely as a result of myofibrillar protein synthesis, defined as the rebuilding of actin and myosin filaments within the muscle fibers. This process requires essential amino acids, particularly leucine, to trigger the anabolic signaling cascade (specifically, mTOR activation). Collagen lacks leucine and contains no tryptophan, rendering it a low-quality protein by most muscle-building standards.
Collagen provides ample quantities of glycine, proline, and hydroxyproline, precisely the building blocks of the extracellular matrix and connective tissue. For these reasons, it appears to support tendon adaptation without meaningfully contributing to muscle adaptation. The two tissues have fundamentally different substrate requirements, and collagen addresses only one, not the other.
Fitting Collagen Supplementation into the Exercise Arena
Collagen peptide supplementation, in conjunction with weight-bearing exercise, can play a key role in managing degenerative bone and joint disorders. This largely results from the combination exerting stimulatory effects on the extracellular matrix of connective tissues, improving structure and load-bearing capacity.
Collagen supplementation seems particularly relevant in populations exposed to high levels of tendon loading, such as athletes participating in running, jumping, and field-based sports. In these sports, repetitive mechanical strain imposes substantial demands on tendon structure, function, and load-transfer capacity.
Mechanical load (think of resistance/strength training in this light) functions as the primary driver of tendon adaptation/rehabilitation, particularly at a load equal to or greater than 70% of an athlete’s 1-rep max. Armed with this knowledge, personal trainers might remind their clients that collagen supplements can only serve as an adjunct to support tendon morphology; collagen ingestion in the absence of a significant mechanical load will not lead to any appreciable tendon adaptation. For patients in tendon rehabilitation, this reinforces the point that collagen supplementation’s role as a connective tissue adjunct must not replace total daily protein from complete protein sources.
As mentioned above, in terms of protein composition, collagen has a unique profile, supplying the amino acids glycine, proline, and hydroxyproline. These serve as the building blocks of the collagen helix and, interestingly, do not occur in significant quantities in most sources of dietary protein. Therefore, when athletes supplement with collagen, they provide their bodies with a key substrate that other protein sources cannot adequately supply.
Countless studies have shown that collagen supplements can sustain tendon health, increase tendon synthesis, and foster a speedier recovery following an injury or surgical procedure. Collagen increases tendon strength, thickness, and cross-sectional area, a key aspect of tendons’ ability to bear a load. Other studies have shown that collagen supplementation may ameliorate or even halt bone collagen breakdown, which typically increases pain for individuals living with degenerative joint conditions.
The Vulnerability of Knees and Achilles Tendons
When the architecture of a tendon degrades and cannot keep pace with the demands placed on it, whether through sports or continual mechanical loading from strength training, pain and dysfunction follow.
How can an individual tell if a tendon injury fails to properly heal? Below, we list several of the telltale signs that a tendon has learned to compensate rather than fully heal:
- Pain that returns following activity, even after a rest day
- Morning stiffness in the Achilles or surrounding the knee
- Pain that improves during a run but worsens significantly afterward
- Persistent tightness that stretching fails to resolve
- Recurrent flare-ups that an athlete has merely “managed” but never fully resolved
The distinction between compensating and healing truly does matter; compensating tendons need a fundamentally different therapeutic approach than acutely sore ones.
Specifically for patellar tendinopathy, a 2023 study demonstrated that collagen peptides significantly increased patellar tendon cross-sectional area adaptation following 14 weeks of high-load resistance training compared with a placebo. When considering Achilles tendinopathy, a 2019 study found that collagen supplementation combined with calf-strengthening exercises improved function and reduced pain compared to exercise alone. However, once again, for challenged tendons in these two areas, a physical therapist would be the best diagnostician.
Commonality Among Injury Locations
Patellar tendinopathy and Achilles tendinopathy rank as the most common sports-related tendon injuries. These two obviously have differences due to their locations; however, some key points remain consistent ~
- As high-load structures, both tend to respond well to collagen supplementation in combination with strength training
- Both respond best when an athlete pairs collagen ingestion with eccentric loading, since passive stretching alone will not drive tendon remodeling
- Chronic cases of pain/dysfunction lasting in excess of six months typically require a longer rehabilitation period before meaningful improvement is felt
The Vital Vitamin C Component
Yet again, vitamin C shines as a key player in human body processes. Scurvy, the classic vitamin C deficiency disease, represents a collagen synthesis failure: joints deteriorate, tendons weaken, and connective tissue breaks down. In active athletes, even a slight subclinical vitamin C insufficiency can significantly impair tendon recovery.
When collagen is ingested with a source of vitamin C, an essential cofactor required for proline and lysine hydroxylation and subsequent collagen crosslinking, these amino acids reach peak serum concentrations after about 1 hour. This practically guarantees their availability during the period of enhanced collagen synthesis stimulated by mechanical loading. This suggests how athletes can maximize the potential of exercise-driven remodeling through strategic nutrient timing.
Some athletes choose to supplement with collagen only on strength-training days, since the body requires mechanical loads for collagen to be incorporated into target tissues. The pairing of at least 50 mg of vitamin C with collagen seems to best facilitate extracellular cross-linking of collagen fibrils. Future studies might consider looking into the dose–response relationship across varied training loads, a minimal effective dose, and long-term adaptations in different populations, including aging adults and athletes undergoing high tendon stress.
Collagen Cannot Solve All Problems
A common occurrence among individuals who find themselves inextricably drawn to supplements is the misguided notion that “if a little works well, more might work better.” When clients ask personal trainers about the advantages of consuming collagen supplements to augment their strength training, we ought to have an honest response, one that reflects the truths about the limits of such supplementation. Below we list a few common facts regarding what collagen cannot do:
- Collagen cannot directly “repair” an existing tendon tear without accompanying rehabilitation
- Collagen must not serve as a substitute for progressive loading and hands-on care
- Collagen may not benefit every tendon equally; most scientific evidence only points to Achilles and patellar tendons
- Collagen cannot serve as a stand-alone fix — it works best as one layer of a comprehensive approach that includes progressive loading, adequate recovery, and appropriate training load management.
Emerging Technology Holds Promise
Tendon healing, a notoriously slow and complicated process, sometimes results in inferior structural and/or functional properties, especially when compared to healthy tissue. New technology suggests that, in the near future, products may exist that can improve tendon healing outcomes. Such devices would enable the enhancement of biological repair through the development of tissue-engineered medical products (TEMPs).
Although many tendons heal with satisfactory outcomes, others do not, leading to discomfort, interruptions in athletes’ lives, and additional cost. Current repair methods seem to lack either native tissue structure or composition, either of which will limit their potential effectiveness. As an example, when attempting to heal an injured tendon, medical technicians strive to restore native organized and dense collagen composition; however, most TEMPs, such as lyophilized collagen or electro-spun pure collagen fibers, remain mechanically weak and unstable. To optimize stability and biocompatibility, scientists now consider the possibility of combining collagen with a high-performance co-biopolymer, such as poly D, L-lactide (PDLLA).
This chemical, a biodegradable polyester synthesized by ring-opening polymerization of D,L-lactide, has an intriguing structure. The amorphous nature of PDLLA arises from the racemic mixture of D and L isomers, making it suitable for applications requiring controlled degradation rates. PDLLA degrades into lactic acid, a naturally occurring metabolite, making it biocompatible and eco-friendly.
PDLLA’s extensive history and well-researched profile enable it to be used in, among other things, “tissue engineering,” which involves scaffolds that promote cell adhesion and tissue regeneration, since it excels at holding tissues together during early recovery and safely breaks down inside the body over time. The future looks promising for its use in tendon repair via reconstructing the complex collagen matrix.
As with any other well-related supplement on the market today, the use of supplemental collagen remains controversial. The points outlined in this article illustrate why personal trainers must take great care in recommending its use to their more serious strength-training clients. Overall, when used properly, collagen seems capable of making a real difference in the healing process of a variety of common tendon injuries.
References:
movephysiotherapy.com.au/blog/collagen-supplementation-tendon-injuries
polysciences.com/products/poly-d-l-lactic-acid-iv-0-4-dl-g
nlphysio.com/collagen-for-tendon-pain-runners-over-30/
canprev.ca/blog/collagen-for-tendon-ligament-injury/
pmc.ncbi.nlm.nih.gov/articles/PMC8521576/
pmc.ncbi.nlm.nih.gov/articles/PMC8792549/
pubmed.ncbi.nlm.nih.gov/30609761/
fitforlifephysicaltherapy.com/collagen-101
pmc.ncbi.nlm.nih.gov/articles/PMC9147671/
nfpt.com/collagen/?srsltid=AfmBOoqENDnRgvbkXEDUsMVx9A1L4v8G5gQphUDGJ4HYQ3u2WoD6Xvhz
