The connectivity of injuries


Muscles, tendons, ligaments and joints are often viewed as mechanical structures and if injury occurs, it’s just unlucky. Ian Craig looks at how to nourish our injuries.

Connective tissue networks

A decade ago, unfortunately after my time as an exercise specialist, there was almost an awakening and the start of a mini revolution in the way that body workers and exercise professionals looked at musculoskeletal health in their clients. Thomas Myers had published his landmark book Anatomy Trains (1), which was a model of human anatomy, a holistic view of the human body that emphasised fascial and myofascial connections. According to Myers, there are three networks within the body which hold it together and allow it to function as synchronously as it does: the nervous system, the vascular system and the network of connective tissue. In this way, 70 trillion cells can live together harmoniously within the confines of our body.

This view of the body as not just a collection of parts mirrors that of Functional Sports Nutrition, which understands the beautiful integration of systems that occurs in order for the body to not only survive, but to thrive. The connective tissue network spreads out from the spine to create a protective net around all the cells, structures and systems. There are front lines, back lines, lateral lines, arm lines and spiral lines that make up this network: the spiral lines are shown in Figure 1. All of the three networks communicate with each other: the nerves carry sensory information in and out of the body; our blood vessels constantly circulate oxygen and nutrients; and the connective tissue system communicates mechanical information via the matrix of fascia, tendons, ligaments, cartilage and bones.


Figure 1: The spiral line of connective tissue (1)

What constitutes connective tissue?

If we focus in specifically on the connective tissue as the basis of the fascia, tendons, ligaments, cartilage and bone plus the structure that binds muscles together, and consider its dynamic role in human movement, we can see that it is potentially a major source of injury for the high achieving athlete, whether elite or recreational. If we break this tissue down further to see what it’s made of, it makes it easier for us to understand how to use nutrition to our advantage. The matrix of connective tissue is made of collagen fibres, elastin fibres, fluid, migrating immune cells, stem cells and long unbranched polysaccharides, called glycosaminoglycans (or GAGs).

If you take a look at Figure 2, we have the example of a load-bearing connective tissue in the form of the cartilage in our joints. Collagen fibrils are represented by the thick striped strands in the diagram and hyaluronic acid is represented by the thin black strands. The brush-like projections coming out of the hyaluronic acid stands are our GAGs, including chondroitin sulphate, which is obviously available in supplement form. The roles of the GAGs are to attract water into the cartilage to give it a kind of padding. The role of the collagen fibres, on the other hand, is to provide structural support to the tissue.


Figure 2: Connective tissue of cartilage (2)

What is collagen?

Collagen, as the structural unit of connective tissue, is the most abundant protein in the animal world, constituting more than 30 per cent of the total protein of the human body (3). It is found mostly in fibrous tissues like tendons, ligaments and skin, but also in bone, cartilage, blood vessels, the gut and muscles. Importantly for our nutrition understanding, it is made out of the amino acids proline, glycine and lysine (4). As shown in Figure 3, collagen fibres are made from three long chains (each about 1000 amino acids long) intertwined in a helical structure. The stability of the collagen fibres are increased by cross-links within the fibres and between adjoining fibres. It is widely known that vitamin C is vital for the cross-linking of collagen fibres (4) and that deficiency of vitamin C can result in distorted, nonfunctional accumulation of scar tissue (5), otherwise known as scurvy. It is the cross-linking that gives collagen its strength and stability. In fact, Yilmaz and colleagues (6) fractured the right tibia of 16 poor rats by digital manipulation and provided a high-dose supplement of vitamin C to half of the animals. It was seen that the group supplemented with vitamin C went through the stages of fracture healing faster compared to the control group.

collagen helix

Figure 3: Triple helix structure of collagen

When injury strikes

In normal tissues collagen provides strength, integrity and structure. However, when tissues are disrupted by injury, collagen is needed for the repair and restoration of function. After injury has occurred, it is the fibroblasts that produce new collagen. Fibroblasts are stem cells that have differentiated into fibrous connective tissue cells in places like tendons and ligaments and they have an important role in wound healing (2). At least 23 individual types of collagen have been identified to date, but type I is predominant in the scar tissue of skin (5). If too much collagen is laid down during repair, the tissue becomes fibrous and if not enough collagen is deposited, the wound becomes weak. The collagen in healthy tissue is strong and organised and on a basis of weight, is nearly as strong as steel. However, collagen fibres in scar tissue are smaller and more random and at best can achieve only 80 per cent of normal strength (5). Since the scar tissue is weaker than surrounding healthy tissue, it will become susceptible to further injury, which makes it even more important to optimise collagen repair, or even better, to reduce the likelihood of injury in the first place.

Genetics of collagen

As noted, there are many different types of collagen depending on which tissue they are most prevalent in. Type I is the most abundant type and is found in skin, bones, tendons and ligaments; type II is mostly found in cartilage; type III is found in the skin and blood vessel walls; type IV is found in secretary membranes; and type V is found in tendons and ligaments (2).

Two collagen genes have received a lot of attention with regards to tendon and ligament injuries. Athletes with a certain genotype for the Collagen 5A1 gene appear to have fewer tendinopathies (7) than the other gene options. These people also seem to have a better range of motion (8), which might further decrease injury risk. Additionally, one of the gene options for Collagen 1A1 seems to increase collagen production and decrease the likelihood of ligament sprains and Achilles tendon injuries (9).

Connective tissue nutrition

The reason I’ve laid down the foundation of collagen and connective tissue physiology for you is that I believe if we understand what the musculoskeletal tissues are made from, we have a better chance of nourishing them through nutritional therapy. We need to remember that all of these physical structures that we’ve talked about are made from certain building blocks that have to come from our diet, so it gives us a clue as to what we should be eating to support them. Collagen has had most of the attention so far in this article, so let’s start with that.


Well-absorbed dietary proteins are extremely important. As noted, the amino acids proline, lysine and glycine are required for collagen synthesis within connective tissue; the branch-chain amino acids (valine, leucine and isoleucine) are needed for muscle synthesis and metabolism (4); and nitric oxide, which requires the amino acid arginine for synthesis, is important for blood flow and collagen synthesis (10). Nitric oxide is normally upregulated following injury, but if inhibited, tendon healing has been shown to be reduced. With this last point in mind, perhaps our favourite sports nutrition supplement of this decade, beetroot juice, could assist with nitric oxide production during injury rehabilitation (11)?

Vitamin C is needed for the structural strength of collagen and has consequently been used to treat many collagen disorders (4). Vitamin C, along with vitamin E and other antioxidants, is also essential to buffer the consequences of oxidative stress, which is likely to be prevalent during injury. Foods high in vitamin C include bell peppers, broccoli, papaya, strawberries, pineapple, kiwi fruit and oranges (12).

Consequently, well-absorbed proteins from the diet are essential for optimal collagen support and healing, and in many cases a protein powder, such as whey or soya or rice, might be useful. Another useful supplement is hydrolysed collagen (discussed on pp26-28 of this magazine), which will provide the appropriate amino acids for collagen repair in an easily absorbable form. Vitamin C can also be supplemented to support collagen, but be aware of the ongoing debate about antioxidant supplementation in sport – some researchers think that excessive quantities might actually impede recovery from training or injury, so think twice before supplementing with high doses.

It would be remiss not to include a mention of bone broths in this article. A good quality bone broth is made using pasture-reared bones, joints, tendons, ligaments, skin and muscle, purified water and a good quality vinegar, boiled in a slow cooker for a long period of time. The end result is normally a gelatinous, nutritious and rich stock that can be sipped as is, or added to foods. According to Melissa Hartwig, consuming broth improves digestion, aids muscle repair and growth, reduces joint pain, promotes a balanced nervous system and strengthens the immune system (13). Additionally, in relation to our feature on bone health (pp12-14), it has been shown that cooking a soup with a beef bone for 24 hours at an acidic pH increased the calcium content of the soup (14).

Glycosaminoglycans (GAGs)

GAGs, as noted above, are vital for the hydration of connective tissue within tendons, ligaments and cartilage. Glucosamine and chondroitin sulphate are major components of GAGs, making them vital for the synthesis of new connective tissue during the healing process. With respect to cartilage repair, glucosamine supplementation has gained most of the research attention and 2000 mg has been shown to significantly reduce joint pain and improve function in as little as eight weeks (15). Sulphation (from the sulphur in either of these products or from MSM) is also important to optimise GAG synthesis for healthy cartilage (16).

Returning briefly to bone broths, in addition to collagen content, hyaluronic acid, chondroitin sulphate and other GAGs are also extracted during the production of a traditional broth.

In conclusion

In addition to consuming sufficient protein in our diet, ensuring sources of vitamin C and potentially supplementing with glucosamine or chondroitin, it is important to eat a diet that is rich in plant foods. Not only do fruits and vegetables boost your daily level of antioxidants, which are important to reduce tissue damage, but they also help to decrease levels of inflammation that might be associated with hard training and injury.


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