We all know, only too well, that to stay healthy, we need to do some physical activity. We also know that there is a lot of information available on what we should and should not do, but sometimes the information seems to be contradictory. How as a lay person, are we supposed to interpret the many studies which have been published?
I have, for many years subscribed, to the idea that we should drink water regularly throughout the day. However I discovered last year that nephrologists had carried out a study into the benefits of drinking the recommended eight glasses of water a day. Clinical studies showed that individuals in hot, dry climates and athletes have an increased need for water but there is no clear evidence of the need for the rest of us. They had no idea in fact where the idea came from! I continue to drink water because I like it, but it did come as a surprise to me, to learn about this work (if you want a bit more detail, go here:http://www.asn-online.org/press/pdf/2008-Media/Water%20Study.pdf).
Having discovered that the benefits of drinking water turn out to be a myth, I was interested to read an article in the New Scientist, early last year which looks at what we think we know about keeping fit and healthy. We all know that exercise is good for us but do we actually know what and how much we need to do?
The article helpfully dealt with some myths. How many of us have used as an excuse the fact that the man, Jim Fixx, who kicked off the jogging craze, died at the age of 52, while running. Of course, the chance of a heart attack while jogging does increase, but we all know only too well that we have more chance of having a heart attack, if we are overweight and unfit. This is why we should check out with our GP what exercise is appropriate for us and then gradually build up intensity and the length of time we exercise. Lots of studies have shown consistently that moderate exercise lowers our chance of a heart attack by 50 to 80 per cent.
Another myth that the article covered is that you cannot be fat and fit. This has, apparently, been hotly debated in exercise science. Clearly, if you are overweight, you are less likely to be fit, right? In 2007, Steven Blair of the University of South Carolina used 2,600 people of varying weight and timed how long they could run on a treadmill before they became exhausted. It turns out that amongst those who were mildly obese, only a third met a ‘common definition‘ of being physically unfit. Only a half of those who were moderately obese were deemed unfit. Blair, in the study, points out that using the measures of aerobic fitness, i.e., the body’s ability to take oxygen to our muscles, has nothing to do with the amount of fatty tissue in the body. He did follow up work for twelve years and found that there was more of a link between the risk of dying and being unfit, than fatness. So, even if you find it hard to lose weight, you should not be put off working at being fit.
The last myth that they deal with is ‘the importance of pushing fluids‘, in order to enhance performance and to stop dehydration. There does seem to be some disagreement about just how much water or sports drink you should take while exercising. What we do have to be aware of is the fact that there has been a rise in exercise-associated hyponatraemia (EAH), a dangerous condition that happens if we drink so much that the level of sodium in the body drops to a dangerous level. This causes brain swelling as excess water moves into that area. In extreme cases, it has caused death. The final thought in this section is that you are more likely to lower performance by over- rather than under-drinking. Sports drinks get a special mention as they usually have sugar but very little salt.
The article also deals with the how much and how often questions. In the past we have been told that exercise should be done most days, usually 30 minutes of moderate intensity, achieving about 150 minutes weekly. However the current advice is that you do need to do about 150 minutes but you can do it whenever it suits. It seems, according to Simon Marshall of San Diego State University that there is no ‘compelling evidence’ that exercising over five days is any better than three or four. Indeed there is also evidence that three lots of ten minutes is just as good as one session of 30 minutes.
The article provides some examples about what constitutes moderate exercise: vacuuming, golf (as long as you walk around the course!) walking (which means walking purposefully, so your heart rate should be up slightly but you should still be able to talk easily), downhill skiing.
I did find one aspect of the article particularly interesting. I find it relatively easy to get fit and build muscle. However I have a couple of friends who have worked just as hard as I have at it, and not had the same results. It seems that fitness level is a very individual thing, as it depends on how the body responds to the activity which is to a great extent determined by our genes. In a study in Canada and the US began in the 1990s, 10% of the population which took part in a vigorous exercise programme lasting 20 weeks, did not experience any change in their aerobic fitness.
However it is not a good reason to do nothing as the 10% did see improvements in blood pressure, cholesterol and insulin levels, and also reduced abdominal fat.
So, get on with it!