Harvard Health Letters

Adults at Forefront of Bicycle Boom - Biking is becoming safer in the U.S., with a growing number of dedicated bike lanes and paths

Harvard Health Letters

Two-wheelers aren't just for kids. Adult cyclists get health benefits, but want safety and comfort, too.

Cycling is more forgiving and inviting than many other forms of exercise. People turn to it partly because it's not as hard on the knees as running and it's usually more convenient than swimming. Heavier people often do well on bikes because cycling isn't a weight-bearing activity, so there's little penalty for girth.

Pedaling a bike strengthens the leg muscles, especially the quadriceps that form the top of the thigh. But for the most part, cycling is an aerobic, not a resistance, workout -- the kind of exercise that gets you breathing harder and your heart rate up and pays cardiovascular dividends. The cardiovascular effects of running and cycling are pretty similar, although running may make the heart work a little harder. In trained triathletes, the maximum heart rate while cycling tends to be about six to 10 beats per minute lower than the rate while running.

Cycling stacks up well against other forms of exercise when it comes to burning calories. A 155-pound person cycling at a fairly leisurely pace of 10 to 12 mph will burn about seven calories a minute. (It's important to specify weight when talking about calories: heavier people will burn more of them than lighter people doing the same activity because they have more mass to move.) A person of the same weight walking at the brisk pace of 4 mph will burn less than five calories per minute. And if the cyclist were to pick up the pace and ride at 14 to 16 mph, he or she will burn calories at the same rate as a runner doing 10-minute miles.


But perhaps the biggest advantage cycling has over many other kinds of exercise, aside from walking, is that it can serve a utilitarian purpose, doing double duty as a form of transportation. Researchers and health officials are starting to look at "active commuting" by bike or on foot as a way for us to meet physical activity guidelines, which set 30 minutes of moderate activity most days of the week as the bare minimum and an hour or more as the threshold for reining in weight gain.

A study in Denmark made active commuting look like a good cholesterol drug: those who biked or walked to and from work had higher levels of "good" HDL cholesterol and lower levels of "bad" LDL cholesterol and triglycerides than those who got there by other means.

Results reported in 2009 in Archives of Internal Medicine were the good news-bad news variety. As in several European studies, those who were active commuters had an assortment of attributes that bode well for wellness, such as a healthy body mass index and good blood pressure numbers, although the association was much stronger for men than it was for women. The bad news is that only 17 percent of the 2,300 Americans in that study were active commuters.

The active commuting studies lump biking and walking together, so you can't attribute all the good results to biking. Another caveat is the problem of self-selection: People who actively commute may be (probably are) healthier to begin with and have other healthful habits. Statistical techniques for controlling for those factors go only so far.


All the health benefits of cycling won't seem worth it if you get seriously hurt in a bike accident. National Highway Traffic Safety Administration statistics show that most years since 2000, between 700 and 800 Americans have been killed in bike crashes. Another 40,000 or so are injured, although the number of reported injuries is probably a fraction of the actual number. The vast majority of the fatalities from bicycle-related injuries are caused by accidents involving motor vehicles.

Relative to the 34,000 deaths each year from motor vehicle crashes (a number that has been declining), the number of bike fatalities may seem low. But compared with other countries, the U.S. is a dangerous place to cycle. An analysis done in 2007 compared rates of cycling injuries and fatalities in this country to those in the Netherlands and Germany on a per-trip and per-kilometer-traveled basis. Calculated that way, the risk of death while cycling was two or three times higher in the United States than it was in those countries, and the risk of injury perhaps as much as 30 times greater.

But there are reasons to be optimistic about American cycling becoming safer -- if it isn't already (some of the crash statistics are quite dated). Studies done in California, Australia, and Europe show that there's safety in numbers: As cycling rates go up, the rate of crash-related injuries goes down. (Keep in mind, though, that even if the rate goes down, the absolute numbers may increase.) Many times, drivers will say after an accident that they never saw the cyclist. Reckless cycling can be a factor. But when cyclists are few and far between, motorists aren't in the habit of seeing them on the road. That should change as the number of cyclists increases.

Cycling is also likely to become safer because of the growing number of dedicated bike lanes and paths, and bike routes, which are regular roads that have some accommodations for cyclists.

In 2009, a group of researchers at the University of British Columbia published a review of the research into the effects that changes in transportation infrastructure can have on bike safety. They identified five studies that showed that the creation of bike lanes and routes, on average, halved the number of bike-related injuries and crash rates. The commonsensical -- streetlights, well-maintained roads -- also made for safer cycling. The verdict was split on riding on the sidewalks, although more studies than not show that it's more dangerous than riding on the street.

Cyclists themselves can do a lot to make cycling safer. The first step is to understand that two-wheeled transport isn't a license to ignore traffic laws. Running red lights and weaving in and out of traffic is courting disaster. Cyclists in urban areas need to be wary about cars parked along the side of the street: running into a car door that has been opened suddenly is one of the most common ways they get hurt. Of course, drivers need to do their part and look in their side-view mirrors before opening the door and getting out of the car.

And there's wearing a helmet. It's true that in cycling-centric countries like the Netherlands, helmets are neither required nor expected. On the other hand, head injury poses the greatest risk to the cyclist, accounting for two-thirds of hospital admissions and three-quarters of deaths. Case-control studies that compare cyclists who have been in accidents without a helmet with those wearing one show that helmet use is associated with fewer head and brain injuries.

Some researchers have argued that helmets have the perverse effect of encouraging cyclists to take more risks because they feel protected, but reviewers have calculated that cyclists would have to increase their risk-taking fourfold to overcome the protective effects of helmets, and that doesn't seem likely.


Most of us learned to ride a bike when we were young, so there's a tendency to view a bike as simple and cycling as an activity that requires no special skill or training. In many ways, that's a good attitude. Why overcomplicate matters and put up another barrier to physical activity? If you're cycling for short distances, or for longer ones only occasionally, just hopping on the bike and going shouldn't be a problem.

But increasing numbers of people are cycling for long distances to commute or as a physically demanding form of recreation. Many cyclists are participating in charity rides of 100 miles or longer that require months of training. Bad technique or positioning or a bike that's the wrong size can make cycling uncomfortable to the point of pain and eventually result in injuries.

High-end bike stores offer bike-fitting services that cost about $100, which will be money well spent if you're cycling a lot. A full discussion of bike fitting -- there are dozens of adjustments that can be made -- and cycling technique is well beyond the scope of this article, but here are a few problems that arise, possible causes, and solutions:

Knee pain

Like runners, cyclists can suffer from patellofemoral pain -- pain from inflammation or tendinitis at the junction of the kneecap (patella) and thighbone (femur). Possible causes include having the saddle too low or too far forward or cycling in too hard of a gear, so pedaling is too strenuous. Pain on the outside of the knee may be caused by irritation of the iliotibial band, a thick cord of tissue that extends from the hip bone down the outside of the thigh to the shin bone (tibia). Causes include a saddle that is too high and pedaling with toes pointed in.

Low back pain

Causes include a bike that is too long or handlebars that are positioned too far forward or too low. The standard recommendation is to keep the saddle level, but one study showed that tipping it forward by 10 to 15 degrees relieved the back pain of cyclists.

Numb hands and wrists

This problem is sometimes called handlebar palsy. It comes from putting too much weight on the hands, so the ulnar nerve that runs from the elbow to the outside of the hand gets compressed. Raising or shortening the reach to the handlebars can help, as can changing hand positions while riding.

Buttock pain

Much of the weight on the saddle should be on the ischial tuberosities, the "sit bones" that form the bottom of the pelvis. Some soreness is to be expected if you're starting to cycle a great deal, but if it's very painful, the saddle may be too high or may need to be repositioned forward or backward.

Erectile dysfunction

Whether this is a genuine problem for cyclists is debatable; study results have been ambiguous. But a bike saddle is certainly capable of compressing blood vessels and nerves in the perineum, the area between the anus and the external genitalia, and perineal numbness is a common problem. A saddle that's wide enough in the back to support the ischial tuberosities can help. Standing up for a few seconds during every 10 minutes or so of riding is recommended. Lowering the seat may also help. - Harvard Health Letter


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Health - Adults at Forefront of Bicycle Boom