The heel tendon and the mythological warrior Achilles are linked by two extremes - strength and weakness. This tendon is one of the strongest in the human body and at the same time one of the most frequently injured. No wonder it was named after the aforementioned hero, regarded as the bravest and immortal, yet with one place vulnerable to blows - the heel.

Heel tendon injuries are very common - especially in physically active people. So it's worth knowing how to take care of this area and safely return to training after an injury. Can collagen speed up the regeneration process? Find out how you can help yourself.

Achilles tendon - anatomy

Where is the Achilles tendon located?

The Achilles tendon (Latin tendo Achillis, tendo calcaneus) is the strongest and thickest tendon in the human body. Interestingly, paradoxically, it is also one of the more injury-prone areas. In the simplest terms, it can be depicted as a tendon that connects the heel bone to the calf muscles. It starts in the middle part of the calf - or, more precisely, at the muscle-tendon junction of the gastrocnemius and sheath muscles. The Achilles tendon is approximately 15 cm long. In terms of width and thickness, on the other hand, it is quite heterogeneous. It flattens at various points (e.g. at the junction with the gastrocnemius muscle) and widens ^{[1, 2, 3]}.

Structure and function of the Achilles tendon

The Achilles tendon is mainly composed of collagen fibres, which provide strength to the structure, but - because they have low extensibility - limit the elasticity of the tendon. They are made up of 90% type I collagen, while elastin accounts for 2% of the dry weight of the tendon (it has a significant effect on the mechanical properties of the tendon) ^{[4, 5]}.

The Achilles tendon enables us to jump, run and other dynamic movements - including walking. Its main function is to participate in the soleus flexion of the foot and to be responsible for the proper function of the lower limb. The vascular territories can be divided into three: with the middle section supplied by the fibular artery and the proximal and distal sections supplied by the posterior tibial artery. The middle section of the tendon is a poorly vascularised area - and it is in this section that most problems occur. The poor blood supply and low innervation of the tendon makes for a relatively long recovery period if an injury is sustained [2].

Overloads and injuries - ruptured Achilles tendon, pulled Achilles tendon and other injuries

Causes of Achilles tendon injuries

Injuries to the Achilles tendon are very common - among the most common of all tendon structures in the human body ^{[2, 6]}. It is the tendon most frequently ruptured and one of the two (next to the patellar tendon) most commonly affected by overload ^[7]. Injuries to this structure usually occur through mechanical loading of the tendon during physical activity. Observations have shown that rupture of the Achilles tendon most commonly affects people who lead sedentary lifestyles and perform sporadic strenuous physical activity. It is also not uncommon for strains in this area to be associated with changes in physical activity - the injury can then occur, for example, when training intensity or duration is increased ^{[7, 8]}. One study found that Achilles tendon problems were most common among runners^[9]. It is noteworthy that during running, the load on the Achilles tendon reaches 9 KN, which corresponds to up to 12.5 times body weight ^[2].

The number and incidence of Achilles tendon injuries has increased in industrialised countries in recent decades. This has been linked to the widespread increase in sporting activities ^[1].
It has also been shown that the Achilles tendon does not have the properties to adapt to high stresses by developing sufficiently high material properties. This exposes the tendon to an increased risk of injury, which may help explain the high incidence of Achilles tendon injuries ^[7].

What are the main problems occurring in this area?

The most common injuries to the heel tendon include:

• Inflammation of the Achilles tendon - this occurs through microtrauma caused by overloading the structure with excessive or sudden stretching ^[10],
• Achilles tendon rupture - partial rupture of the tendon fibres,
• Achilles tendon rupture - a complete rupture of the tendon fibres, which manifests itself with a characteristic and sudden 'snap' in the heel area and complaints of pain and difficulty with movement ^[4].

The most common clinical diagnosis of overload injuries to the Achilles tendon is tendinopathy - a general term for a pathological condition of the structure. It is characterised by a combination of pain and swelling of the Achilles tendon, accompanied by an impaired ability to perform strenuous activities ^[1]. Tendinopathy can result in inflammation of the tendon.

Predisposing factors for Achilles tendonitis include:

• inadequate stretching,
• training errors,
• lower limb misalignment,
• stiff training surfaces,
• systemic diseases [8].

Approximately 75 per cent of all and most partial tendon ruptures are related to sporting activities, usually involving sudden, repetitive jumping and sprinting movements. Complete rupture of the Achilles tendon usually occurs in those involved in dynamic sports requiring running, jumping and fast turns. Many tendon ruptures occur suddenly, without symptoms that could be a warning sign. Studies have also shown that degenerative changes in the tendon occur prior to injury ^[1]. Chronic Achilles tendon injuries manifest as pain, swelling and tenderness combined with impaired performance during sporting activities, and asymptomatic degeneration can occur in 4% of active adults ^[4].
It is also worth noting another type of Achilles tendon injury that is often confused with inflammation. We are referring to tendinosis, which is the degeneration of collagen in response to chronic overuse of the tendon. It occurs when the tendon is not given adequate time to rest and recover from injury by overloading it by repeatedly performing the same movements ^[10].

How to treat the Achilles tendon?

Diagnosis and treatment options. How to regenerate the Achilles tendon?

The treatment of Achilles tendon injuries is selected by the orthopaedic surgeon after interviewing the patient and performing the necessary diagnostic procedures. Imaging studies - such as ultrasound - are often performed to diagnose the damage.
Most people with an Achilles tendon injury respond positively to conservative treatment. Surgery is usually performed on those who - despite following medical advice - do not improve as expected. It is accepted that surgery for a ruptured Achilles tendon should be carried out in young physically active athletes and in those with a relatively late diagnosis of injury or initiation of treatment ^[1]. After surgery, approximately 70-90% of athletes recover ^[11]. Conservative treatment is based on rehabilitation exercises and physical therapy (e.g. shock wave therapy, laser therapy). The rehabilitation process can be complemented by injections ^[12]. In the initial phase of the injury, the specialist may only suggest controlling the inflammation by focusing on correcting training errors, analysing postural defects in the foot and recommending rest and prescribing pain medication ^[3].
How to relieve the Achilles tendon? The key here seems to be taking care of adequate recovery after training and paying attention to correct exercise technique. There is no single treatment that guarantees the best possible outcome. In the recovery process, it is important to correctly recognise the injury and follow the recommendations of a specialist ^[6].

The role of collagen in maintaining flexibility and returning to function after tendon injury

Collagen and its functions in the body

Collagen is an essential structural protein that accounts for 1/3 of all proteins in the human body. It is found in virtually all tissues - including skin, tendons, ligaments, cartilage, muscles, bones, teeth, blood vessel walls, cornea and internal organs - and has a significant impact on the proper functioning of individual systems. It is responsible, for example, for the condition of skin and hair, wound healing processes and the state of the musculoskeletal apparatus - among other things, it ensures the flexibility of tendons and ligaments.
As the body's ability to produce collagen decreases with age, and various external factors (e.g. stress, excessive physical activity, smoking or UV radiation) affect its reduced production, supplementation appears to be a beneficial option - especially for those involved in sport.

Bioactive collagen peptides - what are their properties? How do they affect the condition of the Achilles tendon?

Bioactive Collagen Peptides (BCP®) are physiologically active polypeptides obtained by specific enzymatic hydrolysis of collagen protein. They are characterised by high water solubility, bioactivity and bioavailability and have anti-caking properties.

TENDOFORTE® is a patented and clinically tested bioactive collagen peptide that helps keep tendons and ligaments strong and flexible. TENDOFORTE® has been shown to reduce the risk of injury and improve tendon and ligament flexibility ^[13].

Studies have shown that the intake of TENDOFORTE® collagen peptides by people with chronic Achilles tendon symptoms accelerated the return to running:

This study involved both women and men (runners) between the ages of 32 and 54 suffering from Achilles tendon inflammation. Benefits were noted when taking 5 grams of collagen peptides daily. All participants additionally followed a rehabilitation programme ^[14].

The benefits of TENDOFORTE® supplementation have also been indicated in people with long-term symptoms of chronic Achilles tendinopathy unable to train and unresponsive to any traditional treatments. Taking 5 grams of specific collagen peptides daily in combination with a highly specialised exercise programme allowed the majority of the study group to return to running after just three months. This effect was also proven to be long-lasting ^[13].

Furthermore, certain collagen peptides may be beneficial in both the prevention and rehabilitation of tendon injuries. Taking them at a dose of 5 grams per day in combination with resistance training leads to a better adaptation of the structural properties of the Achilles tendon - an increase in the cross-sectional area of the tendon and an increase in muscle thickness have been indicated. These effects may play a role in reducing tendon stress during daily activities ^[15].

Interestingly, the use of TENDOFORTE® has also been shown to have a positive effect on ankle joint function. Studies have shown that taking 5 grams of bioactive collagen peptides daily for 6 months resulted in improvements in ankle joint stability and reduced the risk of ankle sprains in people with chronic ankle instability. In turn, continued supplementation significantly reduced the possibility of ankle re-injury ^[16].

TENDOFORTE® supplementation thus appears to be a promising support for return to function after Achilles tendon and ankle joint injuries.

OSAVI tendon and ligament collagen - target-oriented supplementation

Collagen Tendons and Ligaments is a food supplement in powder form containing the clinically tested, bioactive collagen peptides TENDOFORTE®. The product is designed for physically active people who need comprehensive support for tendons and ligaments. The product is particularly recommended for women and men aged 25 and over who actively train (e.g. running, climbing, swimming or tennis). The supplement has been enriched with copper and manganese - ingredients that help in the proper formation of connective tissues and their maintenance.

The pack contains 150 grams of odourless, tasteless and easily dissolvable powder - these properties make it ideal as an addition to yoghurts, smoothies or other drinks and meals. The daily serving - 5 grams - is easy to measure thanks to the measuring cup inside.


[1] Järvinen TA. et. al. (2001). Achilles tendon injuries. Curr Opin Rheumatol.; 13(2):150-5. doi: 10.1097/00002281-200103000-00009. PMID: 11224740.
[2] Doral M.N. et al. (2010). Functional anatomy of the Achilles tendon. Knee Surg Sports Traumatol Arthrosc 18, 638–643. https://doi.org/10.1007/s00167-010-1083-7.
[3] Paavola M. (2001). Achilles tendon overuse injuries. Diagnosis and treatment. Tampere University Press.
[4] Freedman BR. et. al. (2014). The Achilles tendon: fundamental properties and mechanisms governing healing. Muscles Ligaments Tendons J. 14;4(2):245-55. PMID: 25332943; PMCID: PMC4187594.
[5] O'Brien M. (2005). The anatomy of the Achilles tendon. Foot and ankle clinics, 10(2), 225-238. https://doi.org/10.1016/j.fcl.2005.01.011.
[6] Szubstarski M. et.al. (2016). Skuteczność leczenia uszkodzeń ścięgna Achillesa. Chir. Narzadow Ruchu Ortop. Pol, 81(4), 133-136.
[7] Wren T. A. et. al. (2001).. Mechanical properties of the human achilles tendon. Clin Biomech (Bristol, Avon), 16, 245-251.
[8] Galloway MT, Jokl P. et. al. (1992). Achilles tendon overuse injuries. Clinics in Sports Medicine; 11(4):771-782. PMID: 1423697.
[9] Kvist M. (1991). Achilles tendon injuries in athletes. Ann Chir Gynaecol.;80(2):188-201. PMID: 1897886.
[10] Bass E. Tendinopathy: why the difference between tendinitis and tendinosis matters. (2012). Int J Ther Massage Bodywork; 5(1):14-7. doi: 10.3822/ijtmb.v5i1.153. Epub 2012 Mar 31. PMID: 22553479; PMCID: PMC3312643.
[11] Kvist M. (1994). Achilles Tendon Injuries in Athletes. Sports Medicine 18, 173–201. https://doi.org/10.2165/00007256-199418030-00004.
[12] Gołos A., Treliński J. (2014). Clinical applications of platelet-rich plasma. Hematology in Clinical Practice; 5(3):252-259.
[13] TENDOFORTE®. STRENGTHEN LIGAMENTS AND TENDONS. Gelita. Improving quality of life. Pobrano 19.05.2023 z https://www.gelita.com/en/products/collagen-peptides/tendoforte.
[14] Praetet S. F. E. al. (2019). Oral Supplementation of Specific Collagen Peptides Combined with Calf-Strengthening Exercises Enhances Function and Reduces Pain in Achilles Tendinopathy Patients, Nutrients, 2;11(1):76.
[15] Jerger S. et. al. (2022). Effects of specific collagen peptide supplementation combined with resistance training on Achilles tendon properties. Scandinavian Journal of Medicine & Science in Sports, 32(7), 1131-1141. https://doi.org/10.1111/sms.14164.
[16] P. Dressler et. al. (2018). Improvement of Functional Ankle Properties Following Supplementation with Specific Collagen Peptides in Athletes with Chronic Ankle Instability, Journal of Sports Science and Medicine; 17, 298-304.