nhsManagers.net | Briefing | 7 January 2018

Medicine for Managers

Dr Paul Lambden BSc MB BS BDS FDSRCSEng MRCS LRCP DRCOG MHSM FRSM

What Happens When I Exercise?

What actually happens when you exercise? The answer is a large number of things.

• Your heart and your respiration rate increase. This enables more blood, and therefore more oxygen and nutrient carrying capacity, to circulate round the body.

• The respiration enables a series of reactions which result in the release of energy which is stored as glucose. The principal mechanism is aerobic respiration where the oxygen inhaled undergoes a chemical reaction with the glucose. The result is that glucose and oxygen are used up and carbon dioxide and water are the waste products, with energy. The energy is used to to enable the

muscles to contract to facilitate movement. Energy is also used to keep the body warm (at 37°C) when the surroundings are colder.

• Therefore, during exercise the muscle cells work harder (respire) and the increased heart and respiratory rate result in more rapid delivery of the glucose and oxygen and more efficient removal of the carbon dioxide and water.

The heart not only increases in rate but the stroke volume (the amount of blood pushed out with each contraction) also increases. The respiratory rate increases and the lungs also expand further, increasing the depth of breathing and increasing the overall capacity.

The lungs, operating at full rate, can increase the oxygen supply

Medicine for Managers articles are not intended to be a source of medical advice. Their purpose is to familiarise the non-medical reader about current key medical disorders. Any medical or medicinal products mentioned by name are examples only and should not be regarded as an endorsement of their use.

A recurring theme in articles about health is just how amazing the body actually is. That is no more the case than when a body switches from its sedentary state to exercising. A series of changes occur which enable the body to perform effectively. Someone can go from sitting in a chair to running in a moment. Great for our predecessors’ survival and with lots of benefits for us too.

by up to fifteen times. The lung capacity is controlled by the muscles of the chest wall and the diaphragm.

Once they are working at their maximum rate, the lungs cannot operate any faster and the VO2 max (the maximum capacity for oxygen usage) is reached. The higher the VO2, the fitter the individual.

• Exercise may place such demand on the body that, despite all the changes, insufficient oxygen reaches the muscles. The body has further capacity in the form of anaerobic (literally ‘without air’) respiration. In this operation, the result is Lactic Acid; an intermediate break-down product which does not require oxygen for its formation. In fact, conversion of glucose to lactic acid produces only about 5% of the energy which the same molecule of glucose produces with oxygen.

• Muscles become tired during long periods of exercise and they stop working efficiently. Lactic acid builds up. It is subsequently removed during rest by being carried away by the blood and broken down or restored to glucose.

• The heart is essential to maximise the ability to exercise. The healthier the heart, the more capacity it has to increase

its output of blood to circulate nutrients and oxygen and carry away waste products. In athletes, the resting pulse rate (the pulse rate when completely at rest) will be slower than the ‘normal’ person and the heart will have additional capacity then to speed up during exercise.

• Joints and Bones work harder during exercise and five times the body weight may be put through them during exercise. This encourages bone to be strong and achieve peak thickness. Lack of use of bones results in loss of calcium (osteoporosis) and increased brittleness. Exercise helps to guard against this.

• The Brain is affected by exercise but in a less clearly defined way. During exercise, the blood flow to the brain increases and many people say that they feel sharper and more focused after exercise. Authorities suggest that regular exercise with the blood flow boost it generates may stimulate brain cell function which, in turn, may reduce the risk of degenerative diseases such as Alzheimer’s and Parkinson’s disease and may further postpone the age-related decline. There is no doubt that increased blood flow to the brain

Medicine for Managers articles are not intended to be a source of medical advice. Their purpose is to familiarise the non-medical reader about current key medical disorders. Any medical or medicinal products mentioned by name are examples only and should not be regarded as an endorsement of their use.

stimulates the production of neurotransmitters which are the chemicals released by nerve ends and which stimulate other nerves to function.

These neurotransmitters include such chemicals as glycine, dopamine, serotonin and also endorphins. These are peptides (protein molecules) which activate the body's opiate receptors, causing an analgesic (pain relieving) effect. Since disturbances in some of the chemicals generated are implicated in the genesis of depression, it is thought that exercise may be effective in the treatment of the disorder.

Other effects of exercise. Virtually every body system is activated by exercise.

• Insulin, produced in the pancreas, diminishes to reduce the storage of glycogen so that more is converted to glucose and then to energy.

• Leptin, a hormone produced by adipose (fat) cells, is produced in lower amounts as exercise is taken regularly and fat stores are diminished.

• Weight loss may be a benefit of exercise as the adipose (fat) tissue is burned to provide energy.

• Those who exercise regularly also notice improved sleep, improved skin health and improved sexual function.

Overall exercise, undertaken appropriately, is a good thing.

Failing to ‘warm-up’ and over-exercising will potentially cause adverse effects and may be potentially very harmful.

Graded exercise is beneficial and, over a period of between two weeks and a year, will bring the benefits listed above.

It is important to remember that fit people can exercise vigorously and more effectively with a quicker return to normal than unfit people.

However fitness is not the same as health. Healthy people are free of diseases but may not be fit. Fit people may not be healthy.

Keeping fit was the priority of primitive man who depended on the fright, flight or fight mechanism, mediated through adrenaline and nor-adrenaline, to enable him or her to remain safe in the face of adversity.

Medicine for Managers articles are not intended to be a source of medical advice. Their purpose is to familiarise the non-medical reader about current key medical disorders. Any medical or medicinal products mentioned by name are examples only and should not be regarded as an endorsement of their use.

These days, over half of all adults in the UK and two-thirds of all adults in the US take little or no exercise at all and, with obesity levels rising, the result may be that the next generation may not live as long as the current generation.

Writing this has had a profound effect on me! I’ve put the sausage roll back in the fridge and have taken the dog for a walk!

Have a good day.

paullambden@compuserve.com

Medicine for Managers articles are not intended to be a source of medical advice. Their purpose is to familiarise the non-medical reader about current key medical disorders. Any medical or medicinal products mentioned by name are examples only and should not be regarded as an endorsement of their use.