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Picture a rubber band with a small section that has lost its elasticity, and instead has become hardened and rather brittle. That's what a trigger point is like: the muscle is tighter, stiffer, will often be weaker and yet very tense at the same time. A TP will be sore when you push on it, and you may feel a thick band that you can flick over with your fingers.

A vast number of sports injuries of all kinds have their genesis in the development of a TP in the muscle or fascia. This TP is very commonly the first sign of overload, and from then on, cause and effect begin to domino: one tissue breaks down, causing another to be overloaded and then break down, and so on. Trigger points lead to inflammation, then pain, then weakness, then joint and nerve dysfunction, and finally structural breakdown of tissues and a severe sports injury that can keep you out of action for weeks, months or even years, depending on how long you attempt to struggle on without treating the original TP.

A TP is thus an alarm bell - a first warning sign that things are not well within your biomechanical system. Learning to listen to your body's alarm bells is a critical skill that can avoid many injuries. Often athletes, with their enhanced overall body sense, become aware of TPs before they are significant enough to cause actual pain(32), when the only complaint is 'tightness' or the joint or muscle doesn't 'feel right'(20).

Arguably, all sports people will develop TPs at some stage in their sporting career. These may hamper our performance and slow us down for a while, or they may blow out to cause a severe injury. They are a normal part of training and competing because our bodies are biomechanically imperfect and our environments more random than we would like them to be. In a perfect world our bodies would not break down when overloaded - and the football pitch would be just soft enough to prevent stress fractures, yet hard enough to prevent ligament tears when we run over a pothole in the grass. But it just ain't so!

To all intents and purposes, a TP is simply a thick knot in the muscle - a way the muscle reacts to being overloaded. In some ways a TP is the equivalent of a stress fracture in a bone. More specifically, a TP is a palpable, tender, nodal point of muscle or fascia. It may also be found in skin, where scar tissue is present, in old ligament injuries or, occasionally, in periosteum (the lining of bone). Under a microscope, TPs appear darker, straightened out and thicker, ranging in diameter from 1-4mm. If located in muscle, they cause it to form taut bands or become 'ropey'. A focal area of inflammation develops fairly early on and a collagen matrix forms; scar tissue is laid down to bridge the weak link, and can become quite thickened and tough, depending on how long it has been present(3,7,8,19,20,23,28). The muscle in which a TP is found will usually be weakened and shortened. The muscle - or the part containing the TP - is commonly in a state of involuntary tension, or increased 'tone'. At worst, muscle spasm will present around a very nasty and inflamed TP, which can result in cramping(21).

The trigger point presents as either

active/'alive' or latent/'sleeping', depending on whether or not it 'refers' pain(3,11,30,32). With an active trigger point (ATP), when you push on the point and try to elicit the 'local twitch response' (an involuntary twitch from the pain of pressing on a sensitive spot), it will begin to cause pain somewhere else in your body on a consistent basis. Latent trigger points (LTPs), on the other hand, are painful only in the area around the TP. The more intense the pain when pressing on the TP, and the more obvious the local twitch response, the greater the likelihood of referred pain being present(12). Sometimes an ATP can even set up 'satellite' TPs in the area to which pain is referred(25).

Apart from finding a sore spot, you can identify a TP in one of three ways:

1. Pain - usually you will start to hurt somewhere(2,4,20,26). Pain may appear at quite a distance from the TP (referred pain) (22,30,32) ; it may surface as a significant injury such as Achilles tendinitis or shoulder impingement(14,16,21) or it may simply hurt like hell in the muscle or joint that has been overloaded. Sometimes the first thing that starts to hurt is a joint associated with a certain muscle: for example, patellofemoral joint pain in the knee may be the first signs of TPs in the vastus lateralis and/or vastus medialis (parts of the quadriceps) muscles.

2. Motor pattern change. Your first indication of a TP may be that things just don't feel 'right'; what was once a smooth action, with power behind it, now feels clumsy and uncoordinated(8, 14, 24). Your lap times are down, and your coach has noticed it too. Somewhere along the line your biomechanics have changed and the firing pattern of your muscles has been altered(32) because muscles with TPs may have a lower firing threshold (ie overactive) or a higher threshold (ie sluggish and late) because of the pain associated with contracting the muscle.

3. Weakness. A muscle with one or more TPs will lose its strength until the TP is treated(8, 14, 20, 24). This is either because its nerve supply is compromised by the TP(14), or because the TP is causing a pain inhibition (ie it hurts to contract the muscle or move a joint associated with it). If a joint is not being sufficiently protected from excessive shear forces by a muscle that is too weak, it will send pain messages, become inflamed and soon start to undergo degenerative changes. In this scenario it is definitely not enough to just get into the gym and 'work through the pain'. Often the pain will get worse unless the TP is being treated at the same time and joint stability and relearning exercises are prescribed.



What causes trigger points?

Broadly speaking, we can divide the causative factors into three categories, as follows:



1. Overuse - extrinsic factors. These include:

Training errors, such as excessive volume or intensity, rapid increase or sudden change, excessive fatigue and inadequate recovery;

Inadequate preparation - including pre-conditioning, warm-up to stimulate blood-flow, appropriate and sport-specific stretch procedures, brain-stimulating movement drills;

Inadequate massage for sore and tired muscles. The benefits of regular massage have been thoroughly proven and one per week is all you need;

Overhard or soft surfaces. The camber of a running track needs to promote balanced muscle development. Moving from outdoor to an indoor track may also have an impact;

Inappropriate/worn out shoes/equipment;

Environmental conditions - too hot, too humid or too cold - can compromise blood and water flow to muscles, thereby affecting their temperature and the flow of minerals required for muscle/nerve function.



2. Overuse - intrinsic factors. These include:

Poor biomechanics. There is no ideal biomechanical system to aim for, but there are principles that allow muscles to remain balanced on either side of a joint. You may have flat feet or poor posture, but the real issue is whether or not your muscles can support that joint. Some of the best sprinters in the world have flat feet, but those feet are extremely well supported to give their muscles a good biomechanical advantage. Having said that, poor foot biomechanics will require good orthotics (arch supports) to prevent TPs developing in the legs or back(24). Good biomechanics will result in proper muscle balance and, consequently, good muscle performance and joint protection. Whenever a muscle or joint is allowed to move repetitively too far beyond its 'neutral zone', TPs will start developing. Thankfully, the body is very receptive to relearning good movement patterns; with concentrated effort, you will be surprised how well it will adapt to moving in a healthier pattern that will maintain muscle balance and keep TPs at bay;

Muscle fatigue. Repetitive movement or loading beyond a certain point will fatigue a muscle and eventually cause it to break down within its structure, allowing a TP to form. This happens regardless of biomechanical issues. Allow time and other helping factors to give the muscle a good chance of recovery;

Muscle weakness. As above, except that endurance is not the issue but rather the muscle's capacity to produce sufficient force under loading. When you are performing a movement pattern under load, eg sprinting from a start, you may not be aware that your gluteus medius isn't strong enough to keep your pelvis in a stable position, so that it is contracting beyond its capacity and developing TPs within it. The first you know about it might be a sore low back or tight, achey hamstrings. Specific strengthening of stability muscles (eg abdominals, glutes and scapular and rotator cuff muscles) as well as the more obvious prime mover muscles (eg pecs, lats, quads and hams) is essential;

Joint instability/hypermobility. If a joint is no longer constrained by non-contractile tissue (eg an ankle that has had a ligament tear) then muscles supporting that joint will be required to overwork to protect the joint from damage. TPs will then develop in that muscle(18, 20, 28);

Lack of muscle flexibility. Generalised muscle tightness will tend to increase the chances of TPs forming(10, 16, 20), but this again has more to do with muscle imbalance around a particular joint. Tightness in specific muscles that are required to be flexible for the demands of the sport - eg hamstrings in rugby goal-kickers - will definitely lead to TPs.



3. Non-overuse factors. These include:

Trauma. Muscle trauma such as a partial or full thickness tear of the calf muscle tissue will inevitably cause widespread TPs. They will also need treatment in the process of rehabilitating the muscle tear;

Post-operative factors. TPs often form during rehabilitation after surgery, as a strengthening regime is carried out. This is due to weakness resulting in muscle imbalance. In a recent study(6), 10 patients with ongoing pain after significant surgery to their knee noticed significant improvement after TP treatment;

Nutritional and health factors(8,20,27). Hypothyroidism, folic acid and iron insufficiency are repeatedly cited in TP literature. A host of vitamin and mineral deficiencies may also have an impact (the Bs,Vit C, Ca, K and Mg). It is logical to assume that unhealthy muscle tissue will have poorer regenerative powers and be more susceptible to breakdown;

Psychological factors. Impaired sleep, excessive stress and depression can be related via psychosomatic pathways (ie body-brain connections). However, TPs also have an impact on your autonomic nervous system and can themselves cause emotional distress(20).



How to find your own TPs

Make sure you and the affected muscle are completely relaxed, not on stretch, then use one of the following techniques to palpate the TP(20,30):

Flat Palpation. This involves simply moving the fingertip(s) transversely across the muscle fibres with some pressure until a 'taut band' is located. Having found this tight section of the muscle, explore along its length to locate the spot of maximum tenderness with minimum pressure: that is the TP. With some practice it doesn't take long to find the taut bands in a muscle. Don't be too worried about the pain you might elicit, because you can't do yourself any harm here!

Pincer Palpation. Some muscles - eg the upper trapezius (neck) or gastrocnemius muscle (calf) - can be lifted from surrounding tissue between the thumb and forefinger to locate the TP. The muscle will usually contain a 'taut band' which contains the TP within it(13,20); if you flick over the right area it should cause a twitch in the muscle or that part of the body, known as the 'local twitch response' (LTR)(3,12,13). If there is no LTR the TP may be more chronic, in which case a part of the muscle will feel like a lumpy rope or knot.

To determine whether the TP is active or latent, apply some firm pressure to the sore area: an ATP will be extremely tender compared to a LTP but, more importantly, it should refer pain to another area in the body. While different TPs refer to different areas, the referred pain pattern is quite similar from person to person. Sometimes a TP needs to be pressed or flicked over for up to 10 seconds before the referred pain becomes evident.

Direct treatment of the TP (as opposed to treating the whole problem, of which the TP is just a part) is relatively straightforward and relies mostly on having 'good hands' that can feel what is happening to the muscle. A muscle that has been released from a TP will feel softer, more malleable and 'loose' to the touch. In this respect TP treatment is more of an art than a science, in that it relies on the instinct and sensitivity of the therapist as he or she works with the patient. For the same reason, many people end up only 80% better after a course of treatment: it takes persistence and patience (and strong hands!) to stick at it until the TPs are released enough to stop causing pain.

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