Tissue Adaption in a Musculoskeletal context and its relevance for injury prevention, rehabilitation and training
Why are adaptions relevant?
Our very survival has depended on adaptive processes.
Humans have always been highly adaptable often because the human species very existence has depended on it for survival. Adaption does not necessarily mean survival of the fittest either, as being fit has not always ensured survival. Those individuals who were best placed (natural selection) to deal with or cope with a particular set of environmental factors survived to pass on their genes to the next generation. For example, an individual could have a specific gene mutation (defect), which made them immune to a particular disease and yet which proved fatal to those without the gene defect. Inevitably, adaptions often result in a tradeoff which can have other consequences. For example, individuals with sickle cell disease are more resistant to developing malaria. However, the resulting change in the shape of red blood cells caused by the disease causes a multitude of other problems. Red blood cells are usually relatively uniform and circular. Various membranes in the body prevent these healthy red blood cells passing from one area to another, based on shape. The change in red blood cell shape caused by sickle cell disease allows red blood cells to pass through these various membranes, which has many adverse consequences. Adaptive processes and the resulting tradeoffs become particularly relevant concerning the musculoskeletal system, as will become all too apparent.
Musculoskeletal System Adaption
As with other tissue adaptions, the human musculoskeletal system adapts to applied forces (gravity or zero gravity in space). That said, environmental factors will also play a part in how the musculoskeletal system adapts to forces. People often seem to forget that gravity is continuously at work and that various parts of our body are heavy. Hence, daily activities result in loads on the musculoskeletal system. Such loads create tensile and compressive forces on multiple structures within the entire body. Besides environmental factors, tissues will adapt according to variables relating to the forces applied to them. Such, variables are highly relevant to Injury Prevention, Healing, Rehabilitation and Performance. In essence, tissues will adapt to changes in the forces applied to them "as is tolerable". Tissues and structures within the body have different properties and respond differently to the type, duration, and frequency of any given force. How tissues adapt will also depend on factors such as genetics, previous injury history, nutrition, hydration and rest. When forces exceed a "tolerable" level, tissues will receive some degree of trauma, be it minor or significant. Hence, some injuries can appear fairly instantaneously, and others can develop over time, depending on the mechanism. General medicine has developed two concepts over the years to explain adaptive musculoskeletal processes Wolff's law and Davis's law.
Bone Adaption and Wolff's law
Wolff's law relates to bone adaption and how bone remodels according to the forces applied to it. Bone's adapt by becoming thicker with "tolerable" loading, and the opposite happens with reduced loading. This concept explains why astronauts suffer from a loss of bone density, as there is no gravity to "stress" or load the bones. Astronauts try and compensate for the bone density loss by exercising in space, which places loads on the bones via muscles. However, even when Astronauts perform exercises, they still lose a great deal of bone density as a result of being in a zero-gravity environment. Some studies have shown that Astronauts can lose between 14 - 30% bone strength in a given six month period in space. Equally, people who are immobile for extended periods are also are more susceptible to adaptive changes to their bones, resulting in osteopenia and osteoporosis. It makes a great deal of sense that general medicine has started to utilise graded load-bearing exercise programs for those suffering from bone density aliments such as osteopenia and osteoporosis. Graded exercises will be patient-specific and take factors such as load, duration, frequency etc. into account. It is also worth noting that various soft-tissues are attached to bones, and thus, adaptions to bones are also likely to affect soft-tissues and overall biotensegrity (see article).
Soft-tissue Adaption - Davis's law
Davis's law relates more to soft tissue adaption, and these changes are more evident to the majority of people. It is relatively easy to see the difference between somebody who is physically fit or goes to the gym versus somebody who does not. Although soft tissues will adapt to the forces that are applied to them "as tolerable" and become stronger, there will still be natural limits on how much they can naturally change. In the case of muscles, muscles may become more substantial, stronger or leaner. However, diet, genetics and the application of forces (the type of training) all play a part. That said, muscles are not the only soft tissue within the body and tissue adaptions are also likely to affect ligaments, tendons, fascia and even joint structures. Again, changes or soft-tissue adaptions will have implications for biotensegrity. The zero-gravity environment of space also has adverse effects on the muscle strength of astronauts too. On earth, the human body continuously deals with the force of gravity and muscles are continually working against this, regardless of activity level. Gravity means that muscles have to work harder when performing any strenuous activity, and the tissues will adapt accordingly. Muscles load bones, via a combination of mass and tensile forces, which again affects bone remodelling (Wolff's law).
Musculoskeletal Adaption and tradeoffs
Sprinters need explosive power, and for a short period, hence the larger frame makes sense. The differences between a sprinter and a marathon runner are relatively simple examples of adaptions and tradeoffs. Each type of runner is tailored to their specific sport, making them good at their particular sport but not the other. There are multi-sport events, and people can adapt to perform at a very high standard in multiple sports (biathlon, triathlon, decathlon, pentathlon). That said, individual world records tend to be held by the sport-specific athletes, e.g. a 200m Sprinter is more likely to have the world records for that event over say a Pentathlete, who has adapted to five sports. Similar could be said about a fly-weight vs heavyweight boxer as there are tradeoffs in speed, stamina, power, endurance and cardiovascular fitness.
Specific training will create adaptions which change the size, strength, weight and endurance of muscles and also tensile forces on bones, joints and other structures within the body. The concept of tensile compressive and tensional forces within the body will be covered more in the article on Biotensegrity, which is a vast topic. Also, we can all have variations concerning, eye, hand and foot dominance and our bodies adapt according to these preferences. Noticeably, somebody who is right-handed is likely to use the preferred or dominant hand more than the left, and the tissues then change accordingly. Many sports involve a unilateral set of motions, and a top athlete's body will adapt to these movements accordingly. Again, such adaptions have tradeoffs or consequences, and one can see the same in the animal kingdom. Lion's are heavily built and muscular and very different in when compared to a Cheetah, which is lean and extremely fast. These adaptions have also partially come about due to how these animals hunt and socialise.
Adaptions to habitual behaviours
Besides training for a specific event or activity, the body also adapts to habitual behaviours. One needs to recall that the human body is continually fighting against the effects of gravity and that our limbs are surprisingly heavy. A human head on average weighs around 10lbs or similar to a bowling ball. Many tissues and structures continually work to maintain a static head position. Habits can increase the loads placed on different tissues and create adaptions affecting compressive and tensional forces on other tissues and structures. Although there is no medically agreed "Gold Standard" correct posture, tissues are loaded (via gravity) based on our position and duration in said position. Hence, this is why "movement" is generally a good thing as it changes the loads on specific tissues and structures and in effect, gives everything a break. Although, we as humans are usually fairly symmetrical, there are differences between each of us, due to genetics, previous traumas, habitual behaviours, diet, hobbies and interests and a multitude of other factors. Such differences make each of us unique, and thus, there can be differences regarding level of comfort or discomfort between two individuals adopting the same posture.
Many modern-day habitual behaviours and even work involve placing a great deal of load on multiple structures and for sustained periods. Muscles usually work in pairs or groups to create movement via alternating muscle contractions. One group contracts (the agonist(s)), while the opposing group relaxes (the antagonist(s)). There are also different types of muscle contractions including Isometric, Eccentric, Concentric and movement requires a combination these. In many respects, maintaining a set position for hours at a time is equivalent to making a large number of relatively small muscles metaphorically "run a marathon". However, running a marathon would involve using larger muscles, all the various types of muscle contractions and a key difference, movement.
People intending to run a marathon also usually start a progressive training program months before the actual event, which allows tissues to adapt to the demands of such a challenge. Even with all of the training and tissue adaption, a marathon will create some level of discomfort either during or after. When holding a set position for hours at a time, tissues are not contracting and relaxing as would typically occur with any activity involving movement. Instead, muscles become placed in a perpetual state of semi contracture and a prolonged type of isometric contraction. Furthermore, such tissues never get trained for such prolonged loading and in many respects are not anatomically or physiologically suited for such demands anyway. Hence, such tissues react to being overused, much like a marathon runner's would if they did zero training before the event. Tissues will then adapt to the demands or excessive demands, which could lead to a combination of changes within the Musculoskeletal system affecting structure, function and soft tissues. Most people would notice such changes as one or a combination of tension, pain, restricted mobility, some types of headaches, neurological changes, or other symptoms.
Adaptions to trauma and healing
Although trauma and healing are two separate topics, they are highly relevant to adaption. Most types of bodily physical trauma result in wounding or damage to various tissues, structures and varying degrees of severity. Injuries are usually painful and result in some form of inflammation and restricted motion. The body then adapts to avoid pain, meaning one might move or walk differently, which creates some level of tradeoff as highlighted earlier. Such changed movement patterns can also become learnt and in effect, the new "normal" way of moving and lead to other tissue irritation or trauma at a later date. Furthermore, injured tissues are anatomically and physiologically different from the original tissues pre-injury, which again can have an impact on biotensegrity. Some readers may remember the 1980's and the fact that foam neck braces were almost a fashion accessory. At the time, anybody who was involved in a car accident or received similar associated neck trauma was placed in a foam neck brace for weeks if not months. General medicine later found, that immobilising neck tissues in such a fashion and for a prolonged period had a detrimental impact on tissue healing and longer-term (chronicity) prognosis. Similar is true for other injuries such as the back and where immobilisation and bed rest was general advice. Thankfully, things have changed a great deal, and the opinion has changed accordingly. That said, you do still occasionally see people in neck braces, but these are usually due to more severe neck pathologies than purely soft tissue damage.
Managing adverse adaptions to minimise the impact
In the simplest of terms, one can try to minimise the impact of adaptions by applying countermeasures. A countermeasure would work by using a specific (force(s)) or set of interventions as an attempt to reverse unwanted adaptions and consequences. Some types of countermeasure work in a self-treatment or maintenance capacity and others may require the help of various professionals. For example, one could use a self-treatment technique such as stretching, a foam roller (see article) or even self-trigger point therapy. Such methods attempt to reduce muscular tension caused by body adaptions resulting from trauma, habitual behaviours, work, sport or a sedentary lifestyle. However, such techniques have limits as to how effectively one can apply them in a self-context and self-treatment can make things far worse. A professional knows which techniques to use in a given situation and which techniques would be contraindicated (make things worse). Another self-treatment option might involve strengthening tissues that become overloaded due to some specific activity or set of activities. Strengthening tissues may make them more "resilient" or less susceptible to fatigue, though again there are limits. Also, pain or discomfort associated with a particular symptom may not be the cause, and so strengthening and or stretching the area could make things better or worse. People often seem to stretch hypertonic (tight) tissues, without understanding why they have become this way. Muscles tend to go into "spasm" as a protective measure, and stretching tissues in such a state tends to make things far worse. It is essential to understand why a muscle appears to be weak, as attempting to strengthen it could again make things worse.
Top-level athletes and Olympians have a range of treatment options available to them and a medical team. That said, many such athletes will also be utilising several self-treatment options daily including, stretching, foam rollers, self-trigger point therapy (see article) etc. However, as mentioned earlier, such treatment methods have limits regarding the scope of what they can treat effectively. A typical Olympic medical team is likely to consist of, Nutritionists, Sports Psychologists, Strength and conditioning coaches, trainers, Exercise Physiologists, Soft Tissue Therapists, Chiropractors, Physiotherapists, Sports Medicine Doctors etc. All of these individual specialities can play a part in tissue adaptions and thus the consequences of adaptions on the individual athlete(s) and overall performance.
It is relatively easy to understand how the more physically orientated disciplines can help with tissue adaption, performance, injury prevention, injury treatment and rehabilitation. However, nutrition provides the building blocks for tissue repair, development and general maintenance of various functions in the body. As with any form of arduous training, the body consumes and needs more resources with increased activity. Adequate nutrition ensures that the athlete(s) get what they need when they need it. Some might be surprised that Psychology is relevant, but high performance requires a mindset and strategies to cope with the stresses of competing at such a high level. Such pressures create various "stressors" on the body, and these have a psychological and physiological impact on tissues and thus adaption (see stress article for more details).
A Chiropractor's and Soft Tissue Therapists Perspective - Adaption
As a Chiropractor and Soft Tissue Therapist, the author frequently treats the consequences of unwanted adaptions, which usually create pain. Such adaptions may have resulted due to a specific event (trauma), a particular sporting activity/hobby or more frequently habitual behaviours. Before training as a Chiropractor and Soft Tissue Therapist, the author served in Elite British forces, and that experience gave him a highly developed level of self-awareness. Such an awareness was critical for understanding when things were not functioning correctly, both physically and mentally. The subsequent Chiropractic and soft tissue training then provided context relating to the biomechanics of the human body and a detailed understanding of functional anatomy. The self-awareness and knowledge of the musculoskeletal system has proved highly beneficial. They have enabled the author to notice small differences or symptoms while performing activities before they become a problem. The author is still extremely active and is a distance runner, cycles, kayaks and enjoys endurance type activities. He finds that the self-awareness gained during his military life is just as relevant today as ever in the prevention of injuries and maintaining performance. However, as with other athletes and the general public, self-treatment has its limits and being physically active and having a physically active job has consequences. The author still gets general maintenance work from Chiropractors and Soft Tissue Therapists every six to eight weeks.Self-awareness and relevance to adaptions
Self-awareness is something that can be developed and learnt, once a person understands how "normal" feels. Unfortunately, and far too often, we take our body's musculoskeletal system for granted. Everything is expected to perform as usual regardless of previous injury history or how we treat our body's. We think nothing of maintaining other aspects of our body (hair, skin, nails, teeth, appearance) or other things in daily life (car, home, garden, bike etc.). Again, there are often consequences of differing levels of severity for not maintaining things and not just financially. In a Musculoskeletal context, gradual adaptions may not become apparent until motions become restricted or more commonly the person is in severe pain. Frequently, adaptions have been progressive and over an extended time before a person seeks outside help. Furthermore, often there has never even been any attempt at any form of self-maintenance. All too often, there is then an expectation that symptoms will resolve in a single treatment or can purely be self-treated. However, as good as the body is at self-maintenance via healing and adaption, there are limits, much that same as with self-treatment. Hence, sometimes the musculoskeletal system needs some external help, and that's where professional assistance comes in.
Although it may be possible to remove or reduce the pain in a single treatment, this does not remotely address all the adaptions that have been occurring over a sustained period. As a Chiropractor and soft-tissue therapist, the author can create a lot of change to the musculoskeletal system in a relatively short space of time or treatment session. Change within the body can be created in multiple ways via, mobilisation, manipulative therapy, soft-tissue therapy, prescriptive exercise and lifestyle advice. However, it is impossible to change all the adaptions that in some cases may have taken months, years or decades to occur. Hence, a treatment plan will involve a series of appointments to treat the cause the resulting adaptive changes. That said, some people will have a single treatment to purely get out of pain and then not follow through with any further appointments until the pain or symptoms return.
Sometimes, removing pain in one region allows one to notice pain in another area, as treatment creates a combination of structural and functional changes to the musculoskeletal system and biotensegrity. There is always an adaption process post-treatment too, as the body becomes accustomed or adapts to the modifications created by treatment. The most noticeable changes occur within the first 24 - 72 hours post-treatment, though one may notice adaptions for up to 7 to 8 days. Adaptions over this time can mean that symptoms can appear to be better or worse and vice versa over the adaption period or that new areas start to ache. A combination of related factors affect how people respond to treatment including:-
- Previous adaptions (to traumas, habitual behaviours, injury, etc.)
- Traumas (historical injuries or wounding, forces involved, unresolved damage)
- Healing (partly based on the severity of trauma and subsequent state of tissues post-injury)
- All of these factors affect overall Biotensegrity (tensile forces within the body)
Hence, the author rarely treats any patient more than once in any 7 to 8 day period, unless they are in acute pain. Furthermore, adaption to treatment is a progressive process. Hence, as a Chiropractor and soft tissue therapist, the author rarely needs repeat and should not need to complete the same treatment at subsequent appointments. Following specific aftercare advice can make a huge difference concerning how fast symptoms can resolve.
Where did the 7 to 8 day adaption window come from (experience)
Throughout the author's life, he has always been amazed by the capabilities of the human body. How it can adapt and the extent to which it can change and recover from traumas and injuries can be quite astonishing. Historically, the author has always had a natural interest in how and why things work the way they do or do not work the way they should. There has also always been an interest in physical activity and a drive to push the limits. At the age of 21, the author decided to walk the entire Pennine Way (268 miles), solo and carrying everything he needed on his back. The experience made him acutely aware of how the body adapts to circumstances or the environment. He naively set off on the Pennine Way carrying approximately six stone on his back. Six stone was a touch over half of his body weight at the time, and he ended up losing around one stone in weight, completing the challenge/walk. Admittedly, the author had no idea how many calories his body would use completing such an endeavour (he is certainly not a nutritionist). That said he later learnt that he was burning somewhere between four and five hundred calories an hour. He had upped his daily calorie intake by a few thousand per day, but clearly, that was no way near enough. Before setting off on the walk, the author was reasonably fit and could easily walk 20 miles in a day without any issues or discomfort. However, his body was not used (adapted) to walking between 25 and 35 miles every day and with six stone, lots of hills/mountains and horrendous weather. The walk took 14 days, and it rained for 11-12 of those days, which had dire consequences for his feet.
Not for the faint-hearted
The author's feet looked like putty after a few days and became excoriating painful day and night, due to a distinctive crushing feeling. Each evening he would tend to his feet and let them dry out and then place new dry socks on in the morning. Unfortunately, the waterproof, breathable lined boots did not dry out until the last few days of the walk. Hence, the fresh dry socks were soaked within 15-30 mins each day and remained so for 12-16 hrs per day. After 4 to 5 days, all of his toenails started to fall off, resulting in the loss of all of them. These did not return for six months. At the time, the author did not realise it, but he was suffering from "trench foot" or "immersion foot" and was very close to the final stages of the condition "gangrene". Besides the feet, other areas were also aching a considerable amount, hips, legs and shoulders in particular. The feet started to feel better after losing all of the toenails. The body seemed to adapt to the weight, terrain, distance and weather between day seven and eight. Bizarrely, there was no aching in the night or on the morning of waking on the eighth day, and everything just felt great. Things felt so good that the author ran lots of sections of the last four days of the walk (with the six stone rucksack).
There was also an adaptive process after finishing the walk, and although the author did not notice it, friends and relatives were commenting for a few days. The comments related to the fact that he looked like he was "bouncing" along when walking. It became apparent that the body was still operating as if it was carrying an additional six stone and was compensating accordingly. Learning from the experience, the author decided to do the Pennine Way again a few years later, though in ten days, which he managed without any issues.
Adaptive Processes, hard learnt experience
The understanding gained from the adaptive processes the author's body went through during the Pennine Way walks proved very useful. The experiences proved invaluable when he later joined the British Army and then served in Elite Forces. The courses for Elite Forces, really push the boundaries of both Physical and Mental Endurance and thus the bodies adaptive capabilities. Like many individuals who have exposure to such courses, one becomes highly attuned to one's body, and when things are not working correctly. Such an "attunement" or "self-awareness" can be critical within the Elite Forces environment. An awareness of "self" and "others" within the team can make the difference between "life" and "death". However, while on such Elite military courses, one can sometimes and has to push the body past its ability to adapt. The author has personally experienced this and the resulting consequences. In his case, he required surgery for a knee injury and subsequently had to spend around 18 months running type activities. Such an injury also meant that he had to go through the entire course process again. During such courses, you understand that you are relatively fit, though measure yourself against your peers. Hence, you do not necessarily realise how much your body has adapted to training. How much the body had adapted became blatantly apparent when the author went for a day out on the Pennines (Castletown) with an old friend and dog. His body had become accustomed to walking up hills and mountains, carrying a substantial amount of weight. Hence, his body happily bounded up the first hill. He only noticed his friend was still near the start when he glanced over his shoulder, and after he got no answer to a question. Hence, the author jogged back down to his friend, only to be greeted with a torrent of expletives. The friend was breathing heavily and sweating buckets, and the author was neither sweating or out of breath.
Article written by Dr Terry Davis MChiro, DC, B.Sc (Hons), Adv. Dip. Rem. Massag., Cert. WHS.