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Exercise in Propaganda

At the moment, outside my window the weather looks something like this…

This has curiously removed any desire I might have had to go for a run, which is a shame. There was a time in the not so distant past where I would have branded this, “perfect running weather,” and raced out to wallow in the mud like a good cross country runner. Unfortunately I am now horrendously unfit and a bit too fond of sofas and central heating. In an effort to coax myself out to do some exercise I have decided to have a root around the internet for some pro-exercise related propaganda (and hopefully some science behind it).

EXERCISE IS GOOD FOR YOUR HEART

We all know this one but the actual number of mechanisms behind this are staggering. I will pick a few out here. Otherwise, being a cardiology nerd, I might get carried away and bore you all to tears…

Regular exercise lowers your resting heart rate and increases your heart rate variability; heart rate variability is important because it means the autonomic nervous system is functioning properly. During heart disease the autonomic nervous system loses its ability to regulate the heart properly.

Exercise reduces the levels of inflammation in the blood (possibly); this is slightly controversial as there is a fair amount of conflicting evidence out there. Cardiovascular disease is an inflammatory process and people with heart disease have higher levels of inflammatory markers in their blood stream. One study showed that putting inactive people on a 3-6 month exercise programme led to a 30% decrease in their levels of C-reactive protein (an inflammatory marker). This is the same effect produced by the statins (drugs prescribed for people with high cholesterol). However, in this and similar studies it wasn’t just level of exercise that changed e.g. people in the study also lost weight. More evidence is needed to see if this effect occurs independent of other factors like weight loss, age and concurrent health conditions.

Regular exercise is anti-thrombotic; regular exercise has been shown to decrease risk of stroke (a blood clot in the brain) and heart attack (caused by blood clots in the coronary arteries).  It does so by increasing the amount of circulating tissue plasminogen activator (a protein in the blood that breaks down clots). It also decreases platelet aggregation (making the cell fragments that form clots less sticky) and decreases the amount of triglycerides in the blood stream (fatty molecules which can clog the arteries). Interestingly enough just after exercise you are more likely to clot with increased blood levels of tissue plasminogen activator and increased platelet aggregation but this effect is short lived. Therefore happily the net effect of regular exercise is that you are less likely to have a blood clot. One fact that should get me out and running today is that the benefit of exercise on blood clotting quickly fades once you stop exercising regularly.

EXERCISE REDUCES THE RISK OF SOME CANCERS (PROBABLY)

This is another controversial one. Most studies that look at cancer across large populations are not controlled trials therefore it is difficult to work out whether reduction in cancer risk is due to exercise alone or whether it is affected by other things such as diet and lifestyle. Increased exercise has been shown to reduce the risk of certain cancers like colon cancer or breast cancer. We don’t know why this happens but there are a number of theories. Regular exercise alters the metabolism of hormones like progesterone and estradiol which are thought to have a role in breast cancer. It also helps strengthen the immune system which is known to have a role in tumour prevention.

EXERCISE HELPS YOUR BONES GROW STRONGERER

Regular exercise improves bone density. Bone responds to the forces exerted on it during exercise by remodeling to become denser and therefore stronger. This reduces the risk of osteoporosis.

EXERCISE IS GOOD FOR YOUR BRAIN

Exercise has been shown to improve cognitive function, a recent study in over 50’s with memory problems showed a moderate but significant increase in cognitive function compared to a control group after they were given a 6 month exercise programme. The exercise group improved 1.3 points on the Alzheimer Disease Assessment Scale (ADAS-Cog). This is better than the 0.5 point improvement seen in patients prescribed the anti-dementia drug Donepezil. Rather amazingly even 18 months after the trial ended, the exercise group still had an ADAS-Cog score higher than that of the control group.

The reason for improvement in cognitive function is not known but studies from animal models show that exercise increases blood supply to the brain and promotes growth and survival of brain cells.

This all adds up to…

People who do regular exercise live longer

This has been demonstrated in various studies but my favourite is a paper that looked at 834 retired Tour de France cyclists from France, Belgium and Italy. They calculated the age at which 50% of this group of aging bicycle lovers had passed away and compared this to the same figure in the general population of their home country. The Tour de France retirees reached a median (average) age of 81.5 years, 8 years older than the population at large. Maybe I should ask for a bike for Christmas…

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