Facts about Fitness

[Guest guest]

The below extracts may be of interest:

Taken from www.newscientist.com

FITNESS FADS

DOES an activity have to get you out of breath to count as exercise? Do you

really have to do half-an-hour a day? Is pumping iron a good way to keep your

heart healthy? These are just some of the dilemmas many of us face when working

out the best way to get fit. The good news is scientists do broadly agree on the

best ways to get fit, they just haven't been very good at telling us what

they've discovered.

" We haven't done a great job of distilling down a large number of studies and

say what this means for the average person who's trying to get in shape, "

acknowledges Simon Marshall, a specialist in exercise and sports psychology at

San Diego State University in California.

Whether because of a lack of information, or because some of us are just plain

lazy, most of us don't do enough exercise. One recent survey in the UK found

that only a third of adults meet the recommended goals for physical activity.

Though we all know that exercise is a good thing, only recently was the extent

of its influence on our health established. In the early 20th century, heart

attacks were growing steadily more common in the west, and they were seen as a

sinister new epidemic. It is now thought there are several explanations for

this, ranging from a fall in infectious diseases enabling heart attacks to take

the lead, to various changes in society that made lifestyles less healthy.

A key insight into the importance of lifestyle came from a 1953 study of London

bus conductors. At the time, London buses not only had a driver but also a

conductor, who sold tickets to passengers after they had boarded and sat down.

Most of the buses were double-deckers, so the conductors spent a lot of their

day walking up and down the stairs.

The landmark study published in The Lancet (vol 262, p 1053) showed that

conductors suffered half as many heart attacks as their driver colleagues. " It

was the first hint that this new frightening epidemic could be linked to the way

we live, " said Jerry , at the time an epidemiologist at the UK's Medical

Research Council, who led the study.

Since 's study, hundreds of other investigations have confirmed the

benefits of exercise on the heart and circulation, as well as on almost every

other system of the body. Diseases that are prevented by exercise include

stroke, cancer, diabetes, liver and kidney disease, osteoporosis and even brain

diseases such as dementia and depression.

What counts as exercise?

The standard advice is we should aim for 150 minutes a week of

moderate-intensity exercise. The tricky question here is what " moderate " means.

Gauging the intensity of an activity by measuring how fast it makes your heart

beat is old hat. These days, metabolic rate is the preferred measure. It is

usually represented in units known as the metabolic equivalent, or MET. This is

the metabolic rate during the activity in question divided by the rate when

sitting doing nothing. Moderate exercise is defined as anything that clocks up

between 3 and 6 METs (see chart).

How much, and how often?

Half-an-hour of moderate-intensity exercise at least five days a week used to be

the required regime to keep fit. Now the consensus is that exercise doesn't have

to be portioned out in daily doses. If you aim for 150 minutes per week you can

divide it up however you like.

That has to be good news for those of us who find it difficult to fit regular

exercise into the daily schedule. So, if you can manage a one-hour hike and an

hour of some energetic sport at the weekend, you only have to find time for

another half-hour bout during the working week. " There's not compelling evidence

that 150 minutes across five days is any better than across three or four, " says

Simon Marshall of San Diego State University.

Another hot question in sports science is what is the shortest period of

exercise that is worth doing. The latest evidence suggests that three lots of 10

minutes, for example, are just as good as one continuous 30-minute bout (Sports

Medicine, vol 39, p 29).

Is pumping iron really necessary?

Several studies have suggested a link between muscle strength and living longer,

but for a long time it was unclear whether other factors were confusing the

picture. People who are muscular are more likely to be thin, aerobically fit and

generally healthy - all features known to extend lifespan.

In the past few years, however, some large, well-designed studies have settled

the question. One study, published in 2008, measured the muscle strength of

almost 9000 American men and followed their health for 20 years. The death rates

among those whose muscle strength was in the bottom third for their age group

was around 30 per cent higher than for the other two-thirds (BMJ, vol 337,

a439).

That link remained even after the results had been adjusted to take account of

the effects of aerobic fitness. " The bottom line is that both strength and

aerobic fitness make independent contributions to health, " says Steve Blair, one

of the study's co-authors, based at University of South Carolina's Arnold School

of Public Health, who helped write the US national guidelines on exercise.

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Carruthers

Wakefield, UK