And how fit are we?
How Fit is the General Population?
‘Any casual observer can tell at a glance I’m not the person I think I am.’ Marty Rubin, writer and humorist
The answer is: a lot less than it should be and a lot, lot less than people think.
The Allied Dunbar Fitness Survey (ADNFS)
The first attempt to assess physical fitness of the UK population was published in 1990 – the Allied Dunbar National Fitness Survey (ADNFS, Fentem et al 1994). This was conducted in a representative sample of English adults aged 16–96 years between February and November 1990. A total of 4,316 participants (76 per cent response rate) were interviewed about a range of sociodemographic characteristics and lifestyle factors, such as diet, physical activity (type, frequency and duration), smoking, alcohol, sleep, stress and social support.
A sub-sample of 2,767 participants also underwent a physical appraisal, which included objective assessment of body dimension, composition, flexibility, and cardiorespiratory and muscular fitness. The findings were shocking. More than seven out of ten men and eight out of ten women fell below their age-appropriate activity level for achieving a health benefit. Overall, about one in six had achieved no activity at all for 20 minutes or more in the past month. The level of inactivity increased with age: 10 per cent of 16–20-year-olds took no exercise, increasing to 40 per cent of 65–74-year-olds. When tested on a treadmill, the proportion of men unable to sustain walking up a gradient of 5% at 3mph rose from 4 per cent in the 16–24-year-olds to 81 per cent in the 65–74 year group. For women, the equivalent proportions were 34 per cent and 92 per cent. The figures for muscle strength were no more encouraging. Fifty per cent of women over 55 were unable to walk upstairs without assistance. Interestingly, although fitness tended to decline with age, many older individuals were as fit as, or fitter than, some of the much younger subjects. Astonishingly, 80 per cent of both men and women of all ages incorrectly believed that they did enough exercise to keep fit – yet more evidence of the human’s capacity for self-deception.
Health Survey for England (HSE)
In my last blog I told you about the Health Survey for England (HSE) and particularly the 2008 survey. As well as investigating the levels of exercise taking in the study group, HSE 2008 also measured fitness levels in a sub-group. Adults aged 16–74 underwent a step test. This involved stepping up and down a single step of a predetermined height at a standard rate for a maximum of eight minutes. The pace of stepping increased throughout the test. Heart-rate measurements were taken during and after the test, then combined with the resting heart rate to provide an estimate of the individual’s maximal oxygen uptake (VO2max, see glossary). The information in the HSE 2008 was analysed to allow comparisons to be made between the HSE 2008 and the ADNFS, which involved converting the results of the step test from the HSE to indicate the percentage of adults who could sustain walking at 3mph on the flat and on a 5 per cent incline. Key findings from HSE 2008 were:
- Men had higher cardiovascular fitness levels than women, with an average level of VO2max of 36.3 ml/min/kg for men and 32.0 ml/min/kg for women. In both sexes, the mean VO2max decreased with age.
- Cardiovascular fitness was lower on average among those who were obese (32.3 ml/min/kg among men and 28.1 ml/min/kg among women) than among those who were neither overweight nor obese (38.8 ml/min/kg and 33.9 ml/min/kg respectively).
- Virtually all participants were deemed able to walk at 3mph on the flat but 84 per cent of men and 97 per cent of women would require moderate exertion for this activity. However, 32 per cent of men and 60 per cent of women were not fit enough to sustain walking at 3mph up a 5 per cent incline. Lack of fitness increased with age.
- Physical fitness was compared to self-reported physical activity. Average VO2max decreased, and the proportion classified as unfit increased, as self-reported physical activity level decreased.
There have been a number of other studies of physical fitness in the ‘population’, but the HSE figures are probably the most meaningful in the real world because they deliberately included as broad a cross-section of society as possible. Longitudinal studies, which examine the same people over a number of years, give more accurate estimates of the effects of age than cross-sectional samples, which examine all the subjects at one point in time.
Physical activity and cardio-respiratory fitness
A large number of clinical studies have confirmed the value cardiorespiratory fitness (CRF) as an indicator of general health and as a risk factor for a number of different chronic and non-communicable diseases. CRF is also a significant prognostic factor for lifespan and healthspan. It is certainly a better predictor of future health than self-reported physical activity. Yet CRF is not included in any of the instruments used to assess risk of common diseases. For instance the QRisk3 which measures the risk of developing cardiovascular disease (heart attacks and strokes) includes such factors as age, BMI, blood pressure, blood cholesterol and even post code – but exercise and physical fitness are ignored.
CRF is a vital measurement, which should be included in routine health checks, risk assessment, treatment recommendations and follow-up evaluation of patient progress. It could also be a very important developmental test for children and adolescents. But in the UK and in most other countries routine measurement of CRF is not carried out.
What could/should be done
Quite a lot actually.
- Deciding a standard, affordable, easily applied and reproducible way of measuring CRF. I would suggest using the Rockport Test which calculates VO2max from the time taken and the heart rate achieved after walking one mile as fast as possible. Adjustments need to be made for those on drugs which slow heart rate (beta-blockers and the like).
- The range of normal values needs to be established with figures for pathological low values. There have been many different studies of fitness levels in different populations (few of truly representative samples). Unsurprisingly these have given widely differing values. The main reasons for this are:
a) Differences in the various samples being tested. It is very difficult to get a truly representative sample, partly because the less physically active will be less willing to volunteer for such studies and partly because an appreciable number will be unable to complete the test. The older the sample the more likely this is, which also leads to artificially high results in older people. Indeed in one study, the oldest group tested were found to be fitter than the younger cohort.
To set normative values for use by the NHS the results of HSE 2008 would make a reasonable start.
b)Differences in methods of measurement. For instance cycle ergometry gives consistently lower figures than treadmill testing.
Medical and political action
Our population is unnecessarily and dangerously unfit and unhealthy. Doctors and politicians need to get together to work out a strategy to improve the fitness of our citizens – Such action could just save the NHS and improve the country’s dire financial situation.
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