Bike-sharing programs have grown in popularity in recent years, with schemes now operating more than 643,000 bikes in more than 50 countries.

 A recent innovation comes from Boston, Mass., where doctors at Boston Medical Center can now write a prescription for $5 access to Hubway, the city’s bike-share program. Memberships regularly cost $80.

Noting that 25 per cent of Boston residents are obese, Kate Walsh, Boston Medical Center’s chief executive, said in a statement that access to the bikes gives residents a way to exercise.

“Obesity is a significant and growing health concern for our city, particularly among low-income Boston residents,” she said. “Regular exercise is key to combating this trend, and Prescribe-a-Bike is one important way our caregivers can help patients get the exercise they need to be healthy.”

Hubway operates 1300 bikes and 140 access stations. The city aims to enroll 1000 people in the Prescribe-A-Bike program, limited to Boston residents age 16 and older who receive public assistance or earn no more than 400 per cent of the poverty level.

Regular exercise, of course, is a key component of good health. Danish scientists have reported that schoolchildren who walked or biked to school performed better than children who arrived by car, train, or bus.

Professor Niels Egelund, who co-authored a study on the matter, said “the exercise you get from transporting yourself to school reflects on your ability to concentrate for about four hours into the school day.”

A recent study of London’s bike-share scheme concluded noted that the city’s bike-sharing program offered health benefits on the whole but added that the benefits are most evident among men and older users.

“The potential benefits of cycling may not currently apply to all groups in all settings,” the study read.

Men’s main benefit was a reduction in heart disease, while women’s was a reduction in depression.

Bicycle riders do face risks from cars and other traffic, as well as from pollution. A study of urban cyclists in Ottawa, Ontario using heart monitors detected heart irregularities in cyclists after riding on busy roads and breathing vehicle exhaust. The study’s authors, scientists from Health Canada, Environment Canada, and the University of Ottawa, noted in the journal Environmental Health Perspectives that their findings suggested that, “that short-term exposure to traffic may have a significant impact on cardiac autonomic function in healthy adults.”

However, computer scientists at the University of California, San Diego tested levels of ozone, nitrogen, and carbon monoxide with small, portable pollution sensors. Study participants carried the sensors while riding, with pollution readings showing on their smart phones. The interface uses the Environmental Protection Agency’s color-coded scale for air quality. Participants noted that pollution levels varied throughout the day and could be substantially different just a short distance away, allowing users to choose a route with less air pollution.

Brisbane and Melbourne operate bike-share schemes, though ridership for both is a fraction of predicted levels. Peter Midgley writes The Bike Share Report and formerly worked as the Urban Mobility Theme Champion for the Global Transport Knowledge Partnership. He’s written that both schemes are underused compared to other systems worldwide, gaining only five to 10 per cent of the usage seen in successful systems.

bike lane

Possible reasons for the low rate of use include the low number and density of bikes and docking stations, hours per day the bikes are available, inadequate infrastructure for many people to feel comfortable biking, and both programs’ helmet requirements, mandated by only four programs worldwide.

The helmet requirement has drawn opposition from a group called Helmet Freedom.

“When MHLs were introduced into Australia, cycling levels dropped by more than 30%,” the group said on its website. “Similar falls have been reported elsewhere whenever helmet laws are introduced. No region with MHLs has ever achieved a high or even moderate cycling modal share, just as no bike-share scheme has succeeded in cities with MHLs.”

A U.S. National Institutes of Health study titled No clear evidence from countries that have enforced the wearing of helmets examined areas that had enacted mandatory helmet laws. Analysis of four years of data from Victoria indicated that head injuries had declined by 40 per cent since the law’s adoption.

“However, the authors could not tell whether the main cause was increased helmet wearing or reduced cycling because of the law,” the report states. “Non-head injuries fell by almost as much as head injuries, suggesting the main mechanism was reduced cycling, with perhaps some benefit from reduced speeding and drink-driving.”