By Camille EbdenBBC News
Many marathon runners, such as Paula Radcliffe, stretch before runs.Stretching before running does not necessarily prevent injury a US study of over 2,700 has suggested.
But the researchers say runners should maintain their current routine, whether or not they stretch, as it is changing that is the problem.
The long established doctrine that it is important to stretch before running has recently become an issue of debate.
This is the first controlled study exploring the link between pre-run stretches and injury risk.
The findings are to be presented to the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).
Worldwide, there are more than 70m people who run both recreationally and competitively.
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As a runner myself, I thought stretching before a run would help to prevent injury”
Dr Daniel PerelesStudy Author Stretching is an important part of pre-run routines for many runners, including professionals such as Paula Radcliffe and the sprinter Usain Bolt.
Surprising resultsDr Daniel Pereles of Montgomery Orthopaedics, Washington DC, carried out the study.
He found that: "The risk for injury was the same for men and women, whether or not they were high or low mileage runners, and across all age groups".
However weight and whether or not a runner had already suffered an injury within the past four months did influence the likelihood of injury.
Dr Pereles found the results surprising and said "as a runner myself, I thought stretching before a run would help to prevent injury".
The study involved 2,729 runners who ran 10 or more miles per week.
The runners were randomly assigned to two groups- a group who stretched for three to five minutes immediately before running and a non-stretch group.
The stretch group runners stretched their quadriceps, hamstrings, and gastrocnemius/soleus muscle groups.
All runners who switched their routines for the study were more likely to experience an injury than those who did not switch.
However, the runners who normally stretch before running but were placed in the non-stretch group, were the most likely to have an injury.
Dr Pereles said this implied "that an immediate shift in a regimen may be more important than the regimen itself".
The popularity of running in the UK has particularly increased over the past two years with record numbers applying for the London marathon last year and new running events emerging elsewhere around the country.
The research was carried out in partnership with USA Track and Field and Simon Fraser University.
