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Exercise

Updated on 5th January 2008 by Dr Charles Tweed

“Run, Forrest, run!” [Jenny's often repeated advice to Forrest in the film "Forrest Gump".]

I suspect it won’t come as a shock to you to realise that exercise is good for you. We are constantly bombarded with messages about how we need to lose weight and do more exercise. What this section is meant to do is reveal just how it is of benefit, and how it has to become part of your every day life. Just like weight loss diets, most people have made resolutions to look like the model on the Nike ad, that start well and fade all too quickly.

How do gyms make money?

Most people sign up in a burst of enthusiasm, go regularly for 2 months or so and then rarely go again. Every time they think of going they feel guilty about how much money it has cost them to have that gym membership that they aren’t using. Unfortunately, that does not spur us on to go more frequently, but quite the opposite. The human mind avoids the subject by putting “gym” in a little box in the corner and never going near it again. Your psyche is fantastic in subconscious avoidance techniques. This is a perfect adaptation to allow normal functioning following a traumatic event, such as bereavement, but not helpful in these circumstances.

So, how is exercise good for you?

Cardiovascular disease

Most of the research published about the health benefits of exercise are on its effects on cardiovascular disease. At the core of the problem of cardiovascular disease is dysfunction in the cells that line your blood vessels. An inflammatory process begins, abetted by a high LDL cholesterol, that causes thickening of the blood vessel itself, furring up of the lumen and an inability for the vessel to relax and dilate. The pathology of these processes is extremely complicated and still being clarified. Exercise, however, seems to reduce the incidence of all the contributing factors. Sedentary people have a 20-50% increased risk of developing high blood pressure compared to active people and a nearly 7 times greater risk of developing heart disease!

Aerobic fitness

Aerobic fitness refers to the body’s ability to transport and use oxygen during prolonged exertion (brisk walking, running, swimming, cycling etc). This exercise has been conclusively shown to reduce the risk of developing heart disease and also for preventing further heart problems in people who already have heart disease. The amount of exercise required to produce a reduction in risk is relatively small – perhaps 700-1000 kcal/week – 1 hour of moderate walking five days a week. Health benefits (lower blood pressure, pulse, lipids) are probably derived from even less exercise in previously sedentary people. The more exercise performed, however, the greater the benefit gained: for each 1000kcal of exercise it is estimated a mortality benefit of 20% is achieved. This means that a progressive and incremental training program is best. Whist a little exercise can help, more is better. The Harvard Alumni Health Study found that men who burned between 2,100 calories per week reduced their risk of heart disease by 10% but those that burned over 4,200 reduced it by 19%. After that the risk reduction seemed to plateau.

The risks associated with exercise are minimal even in the elderly and those with established heart disease (2 fatalities per 1.5 million patient-hours of exercise), provided you start slow and build up gradually. It is recommended you speak to your doctor before starting an exercise program.

Anaerobic fitness

Anaerobic fitness refers to the body’s ability to produce energy without the use of oxygen and is also referred to as strength or resistance exercise. Results from the ongoing study looking at health professionals in the US show that as little as 30 minutes of anaerobic exercise reduced the risk of having a heart attack. Anaerobic fitness is best achieved by getting a supervised program in a gym. It is important to have a program that does not cause injury and does not stress the joints and tendons. Injury will require extensive time for healing, which takes longer and longer as we age, and is counterproductive to maintaining health. It is better to do a slightly lighter program all the time than to go for broke.

Metabolic syndrome (MS)

This condition has been discussed elsewhere but in brief it is an increasingly common health problem characterised by central obesity, high cholesterol, pre-diabetes or diabetes and high blood pressure. The reasons exercise is beneficial for the MS are virtually identical to that discussed above. There are several other mechanisms as well. Part of the problem with the MS is the excess of fat around the middle. Not only is that under the skin (spare tyre) but it is also inside the abdominal cavity and inside the organs like the liver. Recently it has been discovered that it is this fat that is mostly to blame for the changes associated with the MS. Externally people can look fine: not overweight, no significant increase in their waist to hip measurement ratio, yet if they have an MRI scan one can reveal significant build up of intra-abdominal fat. This is becoming increasingly common even amongst SE Asian and Asian populations. This fat is only really treatable with the modification of dietary intake and exercise. A sedentary lifestyle is probably one of the major causes of metabolic syndrome and cardiovascular disease and is increasingly being recognised as a major risk factor to be actively sought and modified. Simply reducing your calorific intake wont fix the problem, the body merely thinks it is going through lean times and goes into “starvation mode” conserving energy in the most efficient manner it can. Primarily, this means breaking down muscle (not good) and preserving fat for the long winter ahead (also not good). A well structured exercise and nutritional programme can work wonders for people.

Type 2 Diabetes

Better diabetic control can be achieved through exercise. It is well documented that improving one’s physique – more muscle and less fat – can improve your diabetic control. In some people with type II diabetes or pre-diabetes who are significantly overweight, merely losing weight and increasing muscle mass has completely reversed their diabetes. Even in people who are not overweight, decreasing intra-abdominal fat (see above) and increasing muscle can either remove the need for medication or decrease the dose of medication significantly. The aim here is to lose fat with aerobic exercise and increase muscle with resistance exercises. Muscles have receptors on them that take up glucose from the blood stream. In diabetes there is an excess of glucose in the blood stream (high blood sugar) and a relative resistance of these receptors to glucose. The more muscle you have, the more receptors you have to take up that glucose. The more exercise you do, the more the receptors need to take up to feed the muscle, and the less resistance they develop.

Osteoporosis

This is the term applied to the thinning and weakening of the bones as people age. When we get old we are more likely to fall. When the elderly (and not so elderly) fall over they break things – most commonly their wrists and hips. People who fall and break their hip have a nearly 50% mortality rate in the next six months. This extraordinary figure represents the associated illnesses in someone of that age but primarily it is a reflection of the loss of ability to bounce back from significant injuries. A huge amount of money is spent every year on the prevention and treatment of osteoporosis each year. It is clear that trying to reverse established osteoporosis is extremely difficult. Preventing it is relatively straightforward. A diet rich in calcium, vitamin D and plenty of exercise will do the trick in most people. The kind of exercise you need to prevent osteoporosis is anything that produces a stress on the bone. Running for lower limbs and resistance exercises for upper and lower limbs are best. The time to start is now. Waiting until you are in the at risk groups (post-menopausal women, elderly men) means it is too late. If you act now, you can build up a reserve of bone mass, which can be maintained as you age. Unfortunately, impact can exacerbate degenerative changes in the joints (osteoarthritis) so a structured approach is best.

Falls

In conjunction with preventing osteoporosis is preventing the falls themselves. A preventative approach is again best:

Strength
Flexibility
Balance

All play a role, and exercises targeted to all of these areas are necessary.

Brain, mood and cognition

If we exercise, our thoughts are clearer. Why, has never really been clearly elucidated but is generally accepted that mental function and learning are improved with physical activity. Personally, I have found studying for examinations much more productive if interspersed with regular breaks for light physical activity and one proper run. There is a decline in cognitive function with age. This is partially due to the effects of cerebrovascular disease (see above) but also a product of the deterioration of intra-cellular processes. We know exercise will help prevent the first of these problems. It is likely that it will also help the second. Exercise produces an increase in the number of free radicals and reactive oxygen species that cause cellular damage, but also increases the amount of compensatory mechanisms to counter them. By producing frequent minor stresses through exercise, you are able to up regulate the defences and prevent the damage that accumulates over the years. Secondly, somehow the plasticity and ability to prevent degeneration is enhanced by exercise, decreasing the amount of decay that is normally seen in aging neurological tissue.

Neurobiology of Exercise

There is also a direct relationship between depression and exercise. People who are feeling down do not have the impetus to exercise – after all, what’s the point – and conversely people who exercise are less likely to develop depression. Exercise causes the release of various neurotransmitters such as dopamine, serotonin and endorphins which make you feel good. There is a clear and proven association between recovery from periods of depression and partaking in regular exercise.