London's cycle hire scheme has had a positive effect on the health of its users, suggests a study in the British Medical Journal.
It says '"Boris bikes" have greater benefits for men than women, and for the over 45s who have more to gain from increased physical activity.
These benefits outweighed the negative impact of injuries and air pollution.
Encouraging more, older people to use the scheme would increase the health benefits, the UK researchers concluded.
The London cycle hire scheme, sponsored by Barclays bank, was introduced in 2010 and championed by the city's mayor, Boris Johnson, to such a degree that the bicycles came to be known as Boris bikes.
The authors of the study, from the Medical Research Council, the London School of Hygiene and Tropical Medicine and University College London, looked at the cycle hire scheme over the course of one year, from April 2011 to March 2012.
They tracked 578,607 users' journeys during this time and used data on physical activity, travel, road traffic collisions and air pollution to work out the health impact of hiring a bike in central London.
They found that the benefits "substantially outweighed" the harms, when the injury rates for hired bike usage were taken into account.
Co-study author Dr Anna Goodman, from the London School of Hygiene and Tropical Medicine, said this confounded expectations.
"When the cycle hire scheme was introduced, there were widespread concerns that increasing the number of inexperienced cyclists in central London would lead to higher injury rates.
"Our findings are reassuring, as we found no evidence of this. On the contrary, our findings suggest that the scheme has benefited the health of Londoners and that cycle hire users are certainly not at higher risk than other cyclists."
The researchers measured the health benefits in terms of Disability Adjusted Life Years (DALYs) - the number of years of life gained or lost to illness, disability or premature death.
For all men in the study, the combined gain was 72 years, while for women it was 15 years.
Among men, almost half this benefit was from reductions in heart disease, while among women the largest benefit was seen in reductions in depression.
But when injury rates for all cycling in central London - not just the hire scheme - were used as a comparison, the benefits were found to be smaller for men, and shrank to virtually nothing for women because of the higher death rate among female cyclists following a spate of deaths in London last year.
Looking at older age groups, the study found that although the injury risks increased with age, the benefits of exercise for the 45-59 age group onwards "substantially outweighed the harms".
In the 30-44 age group, the benefits "marginally" outweighed the harms, the study said, because many of the diseases affected by physical activity are less common in younger people.
Dr James Woodcock, a population health scientist from the MRC Epidemiology Unit at the University of Cambridge, said the health benefits could be even greater if cycling was made safer, as it is in the Netherlands.
"The Netherlands manages to achieve high levels of cycling with low risks, not by focusing on helmets and hi-vis, but by providing high quality infrastructure that physically protects cyclists from busy, fast moving traffic."
Roger Geffen, campaigns and policy director at the national cycling charity CTC, said the health benefits of cycling were well documented but people tended to have an exaggerated perception of the risks involved.
"This can be a major deterrent to cycling. It's not entirely unfounded - we still need to see action to reduce actual and perceived dangers of cycling.
"But you are less likely to be killed in a mile of cycling than a mile of walking. One cyclist is killed on Britain's roads for every 26 million miles travelled by cycle.
He added: "Cycling is far more likely to increase your life expectancy."