MEASURE YOUR OWN PHYSICAL FITNESS Part 2

A Walk Test

For older, less fit people and those with heart or lung diseases the six minute walk (6MWT) is often used and has  been shown to give an acceptable prediction of VO_2max. The procedure is much the same as the Cooper test which I described last week but for six rather than twelve minutes, and walking as fast as possible. If walking that quickly does not make you out of breathe you need to take the Cooper test. If the limiting factor for this walk is anything other than breathlessness (joint pain etc) this test does not give a reliable answer.

Here is a table of expected results at different ages over 65. You will notice that the estimate of fitness given by this method is considerably lower than given by the Cooper test. This is probably because the samples of individuals used to calculate the figures were rather different. I believe that the Cooper Test sample population was rather fitter than the majority of older people and I find the six minute walk test results more convincing for older people.

Six minute walk test results
Men

Women

There are a lot of of formulae for converting distance covered into VO_2max but none is very accurate. Some involve BMI and are very complicated to work out. The best is this:

VO_2max = 0.023 X 6 minute walk distance in metres + 4.95 ml per minute per kg. This works well for those with a maximum distance of 600 metres or less but underestimates VO_2max for those who can go further. For them the Cooper test is more accurate.

How meaningful are these figures?

The figures I have given for average fitness at different ages must be taken with more than a pinch of salt. The average fitness level and the variation in fitness differ from one group to another. There have been many studies to try to determine the average fitness of the population as a whole and the variations from very unfit to very fit – but the results they have produced vary widely because of the way in which the subjects to be tested have been selected and the nature of the testing systems used. In some cases the figures are derived from those who have volunteered to be tested, in other cases the population being tested comes from a particular set such as those seeking routine health checks. In only a few cases the individuals being tested have been chosen randomly from the population as a whole.

Even for the most representative, the average given will exceed reality because there will be a proportion of the subjects who have physical problems which prevent them completing the test. Population measurements only apply to those members who can complete the test – and the proportion who are unable to do this increases with age. Thus the overestimate of population fitness levels is much greater for older age groups.

However I do believe that it can be helpful to know roughly where you fit into the range of possible fitness levels so I have constructed the tables above for this purpose. The figures have been compiled from a number of sources to give the best guesses at each age and sex category.  They are only a guide but give you an idea of where you fit into the scheme of things.

Two additional points. Firstly physical fitness after the mid-twenties declines through life – by about 0.5% per annum in early adult life but getting steeper in middle age at about 1% each year  and accelerating in old age to about 2% or more each year. Worryingly too, comparing results from studies in 1990 and 2008 suggests that the general level of fitness in the population is going down. It is in our hands to reverse this trend!

PS

A recent study from the US of children playing football indicates that the usual post-game snack contains more calories than have been expended playing the game!¹ The researchers found the average energy expenditure for children observed was 170 calories per game while the average caloric intake from post-game snacks was 213 calories. The average amount of sugar consumed post game was a staggering 26.4 grams — the total daily recommendation for kids is just 25 grams — with sugary drinks being the biggest culprits.

1. DOI: 10.5993/AJHB.44.2.6