Cycling and health promotion

The consensus that regular physical exercise is a vital part of maintaining health and wellbeing has existed for at least a decade.¹ The human body is made to exercise, yet our increasingly motorised existence means that we now walk an average of eight miles less each day than our forebears 50 years ago.² Cycling has shown a similar decline: in 1949 34% of miles travelled using a mechanical mode were by bicycle; today only 1-2% are.²

The car, weighing the best part of a ton and often conveying only one person and a briefcase, is a highly inefficient mode of transport. The fumes cars expel cause appreciable mortality³ and are a major contributor to greenhouse gas emissions. The excessive use of motor vehicles severs communities and makes active modes of transport such as walking and cycling more difficult. Yet 70% of all trips made by car are less than five miles long and eminently suitable for cycling or walking.

Regular exercise has worthwhile effects on several cardiovascular risk factors, notably a reduction in blood pressure of 10/8 mm Hg among hypertensive patients⁴ and of 3/3 mm Hg in normotensive people.⁵ Today 70% of British adults take exercise less than once a month.⁶ Although the risk factor changes seem small from the perspective of the individual, across the population they could reduce deaths from cardiovascular disease by a quarter.⁷

Building walking and cycling into daily life is much more likely to be sustainable in the long term than gym based exercise prescription schemes.⁸ We own more bicycles than ever-an estimated 27 million in the United Kingdom-so why do we not use them? The most important deterrent that non-cyclists express is fear of motor traffic. The fear is exaggerated in comparison with the statistical likelihood of injury,⁹ but lowering the speed limit in towns to 20 mph would be a straightforward way of reducing it. Seventy per cent of motorists currently exceed the 30 mph limit in free flowing traffic. The government's recent road safety review passed responsibility for speed reductions to local authorities¹⁰ - with no extra resources to implement them. Compounding this was an announcement by the Association of Chief Police Officers that it will standardise enforcement of the 30 mph limit at 37 mph. This may reflect the realpolitik of British roads, but it is irrational. We know that the difference between 20 mph and 37 mph is quite literally life and death.¹¹ Those with a clear sighted view of road safety issues will continue to press this point.

But the best rule is self rule. Doctors have bought the motor myth as hard as anyone, and it is time to change. We doctors love our status as "essential car users," though whether such claims would stand close scrutiny for the many who use their cars simply to commute to work is questionable. The difficulties of a return to utility cycling-that is, cycling for ordinary journeys such as to work or for shopping-are easily overstated, though neither is it a trivial step.¹² The BMJ is holding a seminar on cycling and aerobic exercise on 14 May followed by a cycle ride (see advert in the classified section). We hope that this and other cycling events organised for the Millennium Festival of Medicine will inspire more than a few doctors to make the change. After all, "do as I do" is more effective advice than "do as I say."

Douglas Carnall, associate editor, BMJ, DC is a volunteer for the London Cycling Campaign.


studentBMJ 2000;08:131-174 May ISSN 0966-6494

1. Mersy DJ. Health benefits of aerobic exercise. Postgrad Med 1991;90:103-7, 110-12.
2. Hillman M. Cycling towards health and safety. London: BMA, 1994.
3. Anderson HR, de Leon AP, Bland JM, Bower JS, Strachan DP. Air pollution and daily mortality in London: 1987-92. BMJ 1996;312:665-9.
4. Fagard RH. Prescription and results of physical activity. J Cardiovasc Pharmacol 1995;25:S20-7.
5. Kelley GA. Effects of aerobic exercise in normotensive adults: a brief meta-analytic review of controlled clinical trials. South Med J 1995;88:42-6.
6. Hillsdon M, Thorogood M. A systematic review of exercise promotion strategies. Br J Sports Med 1996;30:84-9.
7. Rose G. The strategy of preventative medicine. Oxford: Oxford Medical, 1992.
8. Hillsdon M, Thorogood M, Anstiss T, Morris J. RCTs of physical activity promotion in free living populations: a review. J Epidemiol Community Health 1995;49:448-53.
9. Powell KE, Heath GW, Kresnow M, Sacks JJ, Branche CM. Injury rates from walking, gardening, weightlifting, outdoor bicycling, and aerobics. Med Sci Sports Exerc 1998;30:1246-9.
10. Department of the Environment, Transport, and the Regions. Tomorrow's roads: safer for everyone. London: DETR, 2000.
11. Webster DC, Mackie AM. Review of traffic calming schemes in 20 mph zones. Crowthorne, Berks: Transport Road Laboratory, 1996.
12. Forester J. Effective cycling. 6th ed. Boston: MIT Press, 1996.