The practice of yoga started in India about 3000 years ago and continues to grow in popularity all over the world. Yoga is a combination of challenging poses and meditative breathing, exercises seen by many of its practitioners as a way to achieve harmony between body and mind whilst improving the health of both.

Yoga stretches are purported to exert every nerve, muscle and gland in the body, and recent research into yoga has shown that it is beneficial to those with type 2 diabetes, asthma, mental health disorders such as bipolar affective disorder, and yoga has even shown benefit in improving symptoms in patients with advanced cancer. But what happens inside the body during a yoga practice?

The Musculoskeletal System

During exercise such as yoga, blood flow increases to the muscles bringing oxygen and essential nutrients to the active tissues. Increased blood flow allows the muscles to function properly but also helps build muscle strength, allows damaged muscles to repair more quickly, and moves sugar out of the bloodstream and into the muscle, thus lowering blood sugar levels.
Muscles are made up of fibres that interlock with each other like the teeth of a zip. When the muscle contracts, these fibres ratchet along one another making the muscle shorten. Muscle fibres can become damaged in exercise and, if they aren’t stretched, parts of the muscle stay contracted which leads to stiffness and tightness. Yoga poses involve stretching and, by stretching the muscle, the muscle fibres lengthen and re-align. These re-aligned muscle tissues recover better from any damage then muscles which are left contracted.

Over time, with regular stretching, the muscles become more flexible. Extensible muscles are far less susceptible to damage in the future, and put less strain on the body’s joints. Less stress on the joints means less damage to the joints which reduces the chance of developing osteoarthritis.

The Cardiovascular System
While breathing in deeply and slowly exhaling, the vagus nerve becomes stimulated. The vagus nerve is a vital part of the parasympathetic nervous system; this counteracts the sympathetic nervous system which activates our stress responses and our fight-or-flight responses. When the parasympathetic nervous system is dominant, the heartbeat slows, and the blood pressure drops, this is what happens during yoga practice. With regular yoga practice, these changes become sustained, which is why yoga has been shown to improve heart disease.

The Lungs
During deep breathing exercises, the lung tissue stretches. This stretching of the lung tissue causes particular nerves within the tissue to become active, and these contribute to the parasympathetic response which brings with it all the benefits mentioned above.

Exercising and stretching the lungs improves lung capacity which, in turn, improves lung function so that the lungs work more efficiently. Improving lung function is particularly important for those with chronic lung conditions such as asthma or chronic obstructive pulmonary disease.

Hormone Changes during Yoga
During yoga practice, cortisol levels drop. Cortisol is the body’s natural stress hormone releases during periods of physical and emotional stress. Sustained, high levels of cortisol can raise blood pressure, increase the chance of diabetes, cause muscle weakness and wasting, and suppress the immune system.
Regular practice of yoga makes the body more sensitive to insulin which causes sugar to move out of the blood and into the muscles and other tissues. Yoga also causes the insulin-producing cells of the pancreas to be more sensitive to rising blood sugar levels. These two changes keep blood sugar levels low and help to prevent the development of diabetes, or contribute to improving the blood sugar levels of those who already have diabetes. Yoga has similar beneficial effects on levels of cholesterol.

Yoga’s Effect on the Brain
During meditative exercises, there is an increase in the degree of alpha brain waves. Alpha waves are the electrical activity in the brain associated with quiet thoughts and restfulness. They are also involved in feelings of calmness and alertness and studies have shown that, following yoga practice, performance in tasks involving selective attention, hand-eye coordination and quick reflexes improve.
Like many of the changes discussed above, this change in brain activity occurs during practice but, if a practice is regular, it becomes permanent and sustained. It is thought that this may be why yoga seems to help people with depression.

Overall Wellbeing
Yoga brings with it many physical and psychological benefits. Individuals who practice yoga often report higher levels of wellbeing than those who don’t. Furthermore, people with pre-existing health conditions say that they feel their situation, whatever that may be, is improved by yoga compared to those with a similar condition who do not practice yoga. So, overall, Yoga is good for maintaining health, improving health, and helping to cope better with other health problems.