A Review of Pedalling Health

Q: What is Pedalling Health?

A: Pedalling Health is an investigation into medical and other research on the value of exercise, particularly walking and cycling.

Q: What sources were used in their paper?

A: The authors have carefully documented authoritive sources for every medical statement; check their web site to find these sources. In talking about traffic solutions, other sources and/or their own opinions are used.

Q: Who are the authors and what is their background?

A: They are four Australians: Ian Roberts is a Lecturer in science at the University of Adelaide, Secretary of the Bicycle Federation of Australia, and a member of the South Australia State Bicycle Committee; Harry Owen is an Associate Professor in Anaesthesia and Intensive Care at Flinders University; Peter Lumb is a Lecturer in Social Work and Public Policy at the University of South Australia and also Vice President of the Bicycle Institute of South Australia; Colin MacDougall is a Lecturer in the Department of Public Health at Flinders University.

Q: Why are cycling and walking stressed over other exercises?

A: The authors state that exercise needs to be "moderate, habitual, and not seasonal." They conclude that the only activities that fully meet this definition are gardening, walking, and cycling. However, they do not discuss the health aspects of gardening or compare it to the other two. In addition they point out that cycling (and walking) could help environmentally and economically. That is, cycling to work, to school, to run errands, and to visit friends could reduce the use and expense of motor vehicles. They also point out that sports activities or "packaged' exercises that are often advocated for exercise actually involve greater risks. And people are more likely to quit.

Cycling and walking, on the other hand, involve little expenditure for equipment or fees, serve useful daily purposes, are practical for people with various fitness levels - including the least fit, and are attractive to people who don't normally exercise. Special bicycles are even available for those with severe physical handicaps.

Q: What is meant by moderate exercise?

A: This paper shows that exercising at 70% of maximum heart rate is better than exercising at 60%, but says that 2,000 kCal of exercise per week is more important that a few sessions of breathless and sweaty exercise. The most appropriate level of exercise has not been determined.

Q: Other exercises involve greater risks than cycling?

A: Here are the comparative risks of hospital injury for popular sports:
 
 

A: Yes, Pedalling Health doesn't give figures, but says that exercise declines with age, both for the population as a whole and for individuals. Cyclists show a smaller decline than those involved in sports. Lapsed athletes may have a greater risk than the non-sport population. Girls in particular are likely to drop out of exercise activities while in their teenage years, and inactive children become inactive adults. A non-sport exercise such as walking or cycling allows everyone to participate all year round. In particular, walking or cycling to work or school is an habitual, daily activity that should lead to good health. Cycling is also an activity that older people can safely engage in without the risks of more strenuous exercises.

Q: Does it really matter if people get enough exercise and how much does it matter?

A: Looking at the risk of heart disease alone, for men, being sedentary is equivalent to smoking 20 cigarettes a day, having a systolic pressure over 150 mm Hg, or having a blood cholesterol level over 6.9 mmol/L. A sedentary lifestyle also fosters coronary heart disease (CHD), stroke, obesity, and type II diabetes. CHD is the leading cause of death in Australia and has the highest medical costs as well.

Q: What are the benefits of cycling?

A: Cycling on a regular basis

1. reduces the cholesterol levels in the blood.
2. increases the high density lipo-protein/cholesterol ratio in the blood as well.
3. reduces the chances of strokes and heart attacks caused by clotting.
4. reduces the chances of illnesses caused by high blood pressure.
5. is as effective as drugs in reducing high blood pressure.
6. makes obesity unlikely thus helping reduce the chances of diabetes.

A: The benefits of regular exercise begins at 800 kCal of exercise a week, but 2,000 kCal is preferred; that is, from two and a half to six hours of exercise a week for the average commuter cyclist.

Q: What are the benefits of more exercise?

A: Exercising longer has some measurable benefits as well. Exercising more than 2,000 kCal a week led to a 2/3rds reduction in the number of heart attack deaths. The risk of death by heart attack is reduced by 20% by 2,000 kCal of exercise, but 6,000 kCal of exercise will reduce it by over 50%. Beyond that, the benefits level off. (6,000 kCal would be about 18 hours per week of cycling for a touring or commuting cyclist.)

Q: If exercise is healthy, why don't people do it more?

A: Two quick reasons are the amount of time spent watching TV and the amount of time spent in motor vehicles, since people only have so much time. When asked why they didn't exercise more, people in Australia gave these three most common answers: no time 33%, no confidence 23%, and no desire 13%. Some of the reasons for these answers might be people's fears of highly competitive sports or activities and their fear of injury during training. Also, they might find many of the exercise activities promoted to be unnatural to them. High-intensity exercises can require more skill and will that many people have, especially older people and sick people. The chances of injury are greater as well. High-intensity exercises can also cause cardiovascular disease problems. Unfortunately, exercise and fitness are now being marketed as products for those whose health is already in decline. Preventive exercise is much more important.

Q: Is there any correlation between fitness and longevity?

A: One third of all deaths due to coronary heart disease, colon cancer and diabetes are caused by physical inactivity.
 
 

A: The risk of a sedentary lifestyle and the benefits of exercise are independent of 1) high blood pressure, 2) unhealthy lipid ratios in the blood, and 3) being overweight, so exercise benefits everyone.

Q: Well, don't most people get enough exercise anyway?

A: In Australia,

27% of people are sedentary

28% engage in weak exercise (less than 800 kCal or 2 1/2 hours of exercise)

25% get moderate exercise (more than 800 kCal, less than 2,000 - 2 1/2 to 6 hours)

20% get optimum exercise (more than 2,000 kCal or 6 hours of exercise)

Q: But is exercise that important to one's overall health?

A: These are the greatest causes of death in the USA:

A combination of all causes 34%

A sedentary lifestyle 33%

Chronic disease 16%

Tobacco and alcohol 8%

High blood pressure and overweight 7%

Family history 2%

A: One study compared men who happened to walk or cycle with those who were inactive and found that the walkers and cyclists with at least 1,000 kCal a week of expenditure had only 42% of the coronary heart disease of the inactive.

Q: Why is cycling a better exercise than walking?

A: Walking provides less exercise for the heart. In a Finnish study of men and women who had freely chosen their own method of exercise, walkers reached 60% of their maximum heart rate, and cyclists reached 70% of theirs. As a result, the cyclists' bodies improved more: the walkers averaged a VO₂ max of 38 while the cyclists averaged 57. The cyclists exercise was high enough to achieve a training response; that of the walkers was not. The cyclists therefore achieved better health benefits from their exercise.

In a controlled study to check these results, which lasted ten weeks, in which one group walked and one group bicycled, the cyclists showed an improvement of 7.3% in VO₂ max while the walkers showed an improvement of 1.6%. On the treadmill test, the cyclists improved 13% and the walkers 9%, even though the cyclists had started at a higher level.

Q: What is the effect of exercise on specific health problems?

A: For better blood lipid and lipo-protein profiles:

One needs at least 1,000 kCal of exercise a week (2-4 hours)

Benefits accrue up to 4,500 kCal a week (10-20 hours)

Exercise and diet have over twice the benefit of diet change alone.

In four weeks, systolic blood pressure of 97 dropped to 88 with three sessions a week and 84 with seven sessions a week. Here are the effects of exercise on blood pressure in men:

inactive 150/80

moderate 120/70

aerobic 60/30

less than 500 kCal, 47 deaths per 10,000 years

less than 2,000 kCal, 35 deaths per 10,000 years

more than 2,000 kCal, 27 deaths per 10,000 years

Q: We've looked at the benefits. What are the problems caused by cycling and walking?

A: First, it must be recognized that all forms of prevention and treatment have costs and side effects. For example, drugs that treat coronary heart disease are known to also cause depression and sudden death. Because exercise prevents the problem before it occurs, the costs are much lower. However, exercise can lead to injury.

A study made in Australia looked at hospital injuries and compared the time involved in activities to the number of injuries. The results showed that football is 38 times, squash is 26 times, basketball is 22 times, and soccer is 12 times as dangerous as cycling per hour.

It needs to be pointed out that most cycling injuries are minor. Only .5% of cycling injuries are critical as opposed to 3% of pedestrian injuries. Cycling injuries are less serious than those of other road users.

However, 90% of all substantual cycling injuries are from collisions with motor vehicles.

Q: Would you say, then, that motor vehicles are the real problem?

A: It cannot be denied that our preoccupation with the safety of motor vehicle users has been at the expense of cyclists. Automobiles, in particular, create three threats: 1. they are dangerous to their occupants, 2. they threaten other road users, and 3. they encourage a sedentary life.

The policy of designing automobiles and roads to be safe for motor vehicle users alone tends to make cycling more dangerous.

Q: Is the risk of motor vehicle collisions equal for everyone?

A: No, the data shows wide variations according to the age and sex of the cyclist, the type of road being traveled on, and the age and sex of the motor vehicle operator. In particular, teenage cyclists and arterial roads show a much higher rate of accidents. For those over 18, the chart shows arterial roads as having accident rates above 150 per million hours and well below 50 for non-arterial roads. For teens, the accident rate is about 450 per million hours on arterial roads. In the 1991 Australian data, at all age groups, accidents to males outnumber those to females by two or three to one (however, no attempt was made to compare the number of hours of riding or the number of riders between the two sexes). The greatest number of deaths from the same survey is among male children and teens. However, other data shows that males in Australia spend four times as much time cycling as do females, and teenage males do 40% of all cycling.

Q: Are there benefits to other road users from cycling and walking?

A: Walking and cycling are "non-polluting, non-congesting, non-road damaging, non-threatening, health promoting, and environmentally sustainable."

Q: Which is the greater risk to a cyclist, getting killed while cycling or dying from coronary heart disease?

A: For Australian cyclists on the road six hours per week, there is a reduction in risk from heart disease of 85 deaths per 100,000 years and an increase in deaths from cycling of 19 per 100,000 years. Nonetheless, they still have a death rate of 121 per 100,000 years from CHD. There are additional health benefits to cycling as well, which lack exact figures, but they also help reduce the death rate of cyclists at the same time. So, the benefits of cycling greatly outweigh the risks.

Q: What is the single most effective method for decreasing bicycle deaths?

A: When asked this question, Peter Croft, Manager of the Road Environmental Safety, Roads and Traffic Authority of New South Wales identified lowering motor vehicle speeds as the answer. Lowering speed limits would have two results: 1. It would give more time in which to avoid the accident. 2. It would reduce the speed of impact.

Impact speeds in a collision with a motor vehicle largely determine if a cyclist will live or die. Looking at collisions between motor vehicles and pedestrians, at impact speeds below 20 mph, only a tiny number of pedestrians are killed; at impact speeds greater than 30 mph, only about 5% survive. Speed also affects the ability to stop. Between 25 and 50 mph, the distance required to stop triples from 60 feet to 180 feet. Thus accidents are more likely to happen at higher speeds.

One Australian study estimates that pedestrian fatalities would drop by 60% if maximum traffic speeds were reduced by 12 mph (20kph).

I strongly recommend reading Pedalling Health or at least looking at the excellent charts. It is now available from two sources (see the right column for the url's).