Chair of the division of physical activity for health, The British Association of Sport and Exercise Sciences

In 1953, Professor Jerry Morris and colleagues published papers in The Lancet reporting that London bus conductors, who spent their days walking up and down the steps of double-decker buses, had lower rates of heart disease mortality than the drivers of the same buses, and that London postmen who spent their days walking to deliver letters had lower heart disease mortality than their deskbound colleagues who worked as clerks and answered telephones in the postal offices.

During the intervening decades there have been over 50 large population-based studies, which together indicate that those undertaking the lowest levels of physical activity or with the lowest levels of fitness experience almost twice the risk of heart disease compared to their more active and fitter counterparts.

With about a third of all adults in the UK undertaking no physical activity in a typical week and over two-thirds taking insufficient activity to meet current UK physical activity for health guidelines – at least 30 minutes of moderate intensity activity on five or more days of week – the total public health burden of inactivity is high. Recent estimates from the British Heart Foundation suggest that almost two-fifths of all heart disease deaths in the UK can be attributed to the fact that we, as a population, are not active enough.

It has taken a long time for the physical activity message to filter into the consciousness of policy makers and health professionals outside the field of exercise science. However, over the past decade or so, the importance of physical activity for the maintenance of health and the prevention of chronic disease has received increasingly widespread acceptance from government, the medical profession and scientists.

One trigger for the increasing interest in physical activity is the burgeoning obesity epidemic. In 1980, 8 per cent of men and 9 per cent of women in the UK were obese; by 2003 this figure had risen to 23 per cent for both sexes. There is much debate about whether the growing obesity epidemic is a consequence of increased food consumption or reduced physical activity, but what is clear is that we are, as a nation, currently undertaking too little physical activity for our current level of energy intake.

However, to focus on the role of physical activity in reducing the risk of heart disease and preventing and treating obesity is to undersell the benefits of adopting a physically active lifestyle. For example, there is evidence to suggest that active children may perform better at school, and that being physically active helps older adults to maintain their independence for longer. There is also an increasing body of evidence indicating that physical activity helps cognitive function throughout the lifespan and can promote neurogenesis – the growth of new brain cells – providing scientific evidence in support of the Roman saying, Mens sana in corpore sano, a sound mind in a sound body.

There is still much work to be done and exercise scientists can play two important complementary roles. The first is in research. We need to understand more about the mechanisms by which physical activity is beneficial to health; we know that being active is beneficial but there is still much to be learnt about how being active benefits us.

Why, for example, do some people lose weight easily when they become more active, but others struggle? Do different people need different amounts of activity for optimal health? And how do we identify those who need to do more... or less? The list goes on. Undertaking a career in research will require further study beyond an undergraduate degree, usually to PhD level and increasingly to postdoctoral level.

The second important role that exercise scientists can play is through applying currently available knowledge to increase physical activity levels. This could take place in a variety of contexts, for example, by working as a GP referral exercise consultant or a clinical exercise physiologist in a cardiac rehabilitation setting. One initiative that BASES is launching later this year to facilitate career development for those wishing to work in this area will be an accreditation scheme for "Exercise Science Practitioners".

Accreditation will be available to those with a degree in sport and exercise science, with sufficient experience of exercise testing and prescription in populations with different health conditions, who can demonstrate that they possess a specific list of skills and competencies. Accreditation will enable exercise science practitioners to show that they are high-calibre exercise professionals. More information will be available on the BASES website later in the year.

The writer works at the Institute of Biomedical and Life Sciences, University of Glasgow. Further information on careers in the sport and exercise sciences is available in the BASES career guide, available free on the BASES website at www.bases.