Stress is a very physical event. We feel stress most clearly in our muscles, particularly in the neck, shoulders, back and face. We even use the words ‘stress’ and ‘tense’ interchangeably. “I feel tense’ means the same as “I feel stressed.”

It is easy to see why. The stress response is all about physical activity. Because we now lead such sedentary lives, we forget how much our bodies and minds are engineered for movement. The stress response has one goal alone, namely purposeful action.

Sympathetic arousal is all about the muscles involved in fight-or-flight. Adrenaline causes muscle fibres to contract. Cortisol provides those muscles with glucose. The increased heart rate and blood pressure speed delivery of supplies to the muscles. The increased breath rate supplies the oxygen to burn energy within the muscles. Because sympathetic arousal always increases muscle activity it should be no surprise that chronic stress leads to muscle dysfunction and pain.

A stress response starts in the emotional brain. The amygdala detects a problem and initiates the contraction of big and small muscles throughout the body. This ‘coiled spring’ feeling is called ‘a preparatory set.’ The body is setting itself up in preparation for action by tensing the muscles appropriate to that task.

This is exactly how a zebra feels just before it flees from a lion. So why is that zebras don’t get ulcers and we don’t? After all they face lions. We can get ulcers facing a computer screen.

The answer is simple. The zebra gets to run and we don’t. The zebra breaks out of its preparatory set and its muscles are freely used for the purpose they were designed for. They stretch and contract fully. They become well suffused with blood and oxygen. The zebra’s muscles get a few minutes of high quality, life-enhancing exercise which also enables them to easily return to rest afterwards. In contrast, we hardly ever get that opportunity. Because we remain tense, we face a different kind of muscle strain to the zebra.

We are like a runner forever at the starting blocks of a race. A runner has to prepare to run and to simultaneously inhibit that impulse until exactly the right moment. If he had to hold that position for minutes, the strain would become unbearable.

This is called isometric tension. Certain muscles are contracting while opposing muscles also tense up to inhibit their movement. The muscles are burning a huge amount of energy with no visible movement to show for it. This is how we can get very tense and very tired just sitting at a desk. We would use less energy going for a walk.

Chronic tension is bad for the body in many ways. It stops muscles relaxing as fully as they might. It impairs the metabolic activity within muscle cells. It is painful in itself and it contributes to muscle injury. It inhibits other bodily processes that rely on good muscular activity. It distorts our posture, and it makes us feel old and miserable before our time. I’ll now elaborate on each of these points.

Chronically tight muscles can’t relax completely even when they have the opportunity to do so. It is not easy to shift from isometric tension to full relaxation. If you’ve been tense at a desk all day, your muscles won’t relax completely as soon as you lie down in bed. Tight muscles need to be stretched out through activity or exercise to relax well.

If our muscles have been tight all day long, they will remain partly contracted even in sleep. This means that our sleep can be edgy and disturbed and we can wake up still feeling tense. Because our mood is our mental interpretation of bodily sensations, this residual tension can make us feel anxious even before the day has begun.

Muscles need to expand and contract fully to be well suffused with blood. Because tense muscles stay in the contraction phase, this partially chokes their entries and exits. Tension impeds the flow of blood, nutrients, oxygen and chemical messengers into the muscles, and inhibits the flushing out of waste products. This explains the dull ache of tight muscles. The gates are choked, supplies can’t get in and waste products can’t get out.

Chronically tight muscles often develop nodules of pain and are more prone to injury. When a sudden load is put on a tight muscle, it is more likely to tear than stretch. These injuries are often so tiny we barely notice them. We just feel rather stiff and sore in general.

Many systems in the body such as breathing, blood circulation and peristalsis depend on rhythmic muscular contraction and expansion to function well. A tight musculature clamps down on these, disturbs their rhythms and makes their work harder.

Our lymphatic system which fights infection and removes waste products doesn’t have a pump like the heart. Its vast network of tubes and glands is completely dependent on adjacent muscle activity to move the lymph up and around the body against the pooling effect of gravity. If this system becomes stagnant because of restricted muscle movement, it is less capable of fighting disease and is more vulnerable to being infected by the pathogens it is trying to destroy.

Muscle pain make us feel old. Tight muscles don’t function well and tend to atrophy. They lose their ability to relax completely. They are like muscular straps that are tightened a little more each year. Worry makes the neck and shoulders tighten, pulling the shoulders forward. By middle age it can permanently hunch the upper back.

Once a muscle is injured, the adjacent muscles stiffen around it to act as a splint. This protective tightness makes them also prone to injury. Chronically tight muscles may continually suffer such micro-injuries and become weakened by expanding areas of scar tissue. This is commonly the scenario behind back pain.

Chronic tension doesn’t feel at all good and we start to move cautiously to avoid hurting ourselves, like old people do. Occasionally we see an older person who has retained the suppleness of youth, and we realise a tight closed-in body is not an inevitable consequence of ageing. It is however a very common one.

Stress always involves muscle tension. Fortunately, it is one part of the whole stress dynamic that we can easily do something about it, and the entire body benefits if we do. If we feel our muscles relaxing, we know we have activated the other aspects of the relaxation response as well. Because the body is so interconnected, we can be confident that heart rate, blood pressure and cortisol secretion will be returning to normal. Digestion and immunity will be able to function well again. Muscle tension is a marker for the whole stress-relaxation dynamic in the body.

So how does sitting still, focusing on the body and letting go thoughts help muscles relax? The simple answer is that it induces the relaxation response and homeostasis. It weakens the thoughts that prime us for action.

The two most common types of meditation are those that focus on the breath and those that systematically scan the body. The latter is particularly useful for muscle tension and there are many ways to do it. You can scan quickly or slowly, up or down, to read the body in detail. You can scan up or down the central axis to induce stillness and balance. You can progressively tense and contract the major muscle groups, or scan using an affirmation or a visualisation. Any way you do it will enhance your awareness of your body as it is in the moment and so accelerate relaxation.

Scanning the body carefully brings our hidden tensions to the surface. It allows us to relax those muscles that are within our conscious control, and encourages those that we can’t control to relax in their own time. It lets us to notice chronic tension and pain while letting go our tendency to unconsciously overreact to them. It enables the body as a whole to relax even if some areas remain painful or tense.

Bodyscanning eventually gives us a detailed understanding of how the body feels when it is tense, how it feels when it is relaxed and how it gets from one state to the other. If we understand the process, we know what to expect and what to aim for.

When we meditate, we notice the concrete in our shoulders turning back into living flesh. We feel our face loosening and our breathing becoming soft and gentle. This effect filters down to the thousands of muscles, big and small, around the body. We can feel this process as a ripple of subtle sensations, a tingling or warmth in the body, as the knots untie and the juices start to flow again. Headaches and stomach aches fade. Pains disappear or become more tolerable. The muscle stiffness dissolves, and our bodies become comfortable places to inhabit again.

If we focus on the body it relaxes. In fact any inward-looking activity that enhances bodily awareness, such as yoga, tai chi or Feldenkrais, has this effect. Yet there is a mystery here. How is that focusing on the body, which is a kind of doing, induces relaxation, which is all about letting go and non-doing? And how is it that focusing, which is always conscious and localised, can produce the huge range of automatic, integrated, whole-body responses that go with relaxation?

Focusing induces relaxation but not as a simple cause and effect. We can flex a muscle at will, but we can’t easily do the reverse. We can’t usually order tight shoulder or stomach muscles to relax immediately. Relaxation works because is a kind of not-doing, an abandonment of effort. Yet focusing on the body somehow sets off a chain of reactions that allows it to relax.

Focusing highlights whatever we focus on. It clarifies our whole-body sense of who we are and how we feel at any moment. This self-observation doesn’t in itself make anything happen, but it feeds accurate, up-to-date, detailed information into the black box of the brain. In particular, it flags the tensions, pains and discomfort since noticing these is more important for our well-being than feelings of pleasure.

The homeostatic mechanisms in our brain are finely attuned to whatever is out of balance, and most of their corrective activity happens below the surface of consciousness. By consciously focusing on the body however, we supply the brain with an extra loop of high-quality information about what is wrong. This helps it recognise when arousal levels or local tensions are excessive so it can make more accurate adjustments to remedy the situation.

Meditators know that this is not just a theory. If you focus on a stubborn shoulder pain, it often becomes warm and tingly and gradually loosens up. The conscious mind flags the problem and the unconscious mind solves it.

Of course, we normally we spend very little time observing the sensations of our bodies. This is what makes meditation such an unusual activity. Yet we only need to do it for more than a minute or two, and it sets off the whole cascade of the Relaxation Response.

The health benefits of meditation come through from this increased body awareness. In practice, this is a tradeoff since we don’t have unlimited resources. It means we spend a little more time each day tuning into how our bodies feels and a bit less to the scatter and trivia of what happens around us. Although most people meditate by sitting or lying down, we can also become well-attuned to the body while we move. We can tell from the speed and quality of our movements how tense or relaxed we are.

When we tune into our bodies, we first notice what is out of balance. If we recognise our shoulders are tight, they can release immediately. If we don’t recognise it, they stay tight. We only relax when we realise that we’re stressed. If we’re aware of tension we can release it. If we’re not aware of it, it can stay for years.

As a corollary to this, the more quickly we notice the signs of stress, the more quickly we relax. We can shed the unnecessary arousal while at work, rather than waiting until bedtime. We can turn the stress around at an early stage rather than waiting for the crisis. We can choose to loosen up now rather than waiting for retirement.