It is widely believed that stretching improves running performance and lowers the risk of injuries. But, a group of researchers say that belief is a myth. Instead, they say an active warm-up can help with running performance and progressive training can reduce injury risk.

The researchers are the creators of an infographic series for the British Journal of Sports Medicine. The series is designed to separate truth and myths about running.

The research team says there is evidence that stretching could help keep joints moving well. But they say it does not help, or harm, performance.

James Alexander with La Trobe University in Melbourne, Australia, is the lead writer of the series. He and his research team are physiotherapists and runners themselves.

In an email to Reuters Health, Alexander wrote that runners have some beliefs around running injury risks, injury prevention and performance that oppose current research. He added that such beliefs cause runners to continue using ineffective methods in their running training.

The team of physiotherapists work with runners of differing abilities and strengths. They discuss myths and facts about running with their patients. They created the series of five "Running Myth" infographics to inform other runners.

The latest deals with static muscle stretching -- lengthening a muscle to the point of tension for 30 seconds. Many runners falsely believe this can reduce injuries. Runners also sometimes use static stretching to reduce muscle soreness after difficult runs, but research does not support this idea either.

However, after a run, stretching can improve joint movement and help runners relax, the researchers note.

Since running puts stress on the joints and soft tissues, runners have a high risk of suffering joint pain, shin splints, and other problems. These often happen when runners too quickly increase how often, how hard, or how long they run.

The infographic suggests that runners build their performance through progressive training. It should start with an active warm-up that involves 5-10 minutes of walking or jogging. They could include 6-8 dynamic stretches. That kind of stretching moves the joints fully. Runners can do this especially in the lower parts of the body, such as doing walking lunges and leg swings. In addition, the researchers suggest ending the warm-up with three short, quick runs at the goal running speed, such as three fast 100-meter runs.

The infographic creators say that warm-ups improve running performance but are not proven to reduce injuries. Progressive training and the improved running performance itself will do that, they say.

Richard Blagrove is a lecturer and researcher at Loughborough University in the United Kingdom. He was not involved in the infographics. He said many runners stretch because joints and muscles start to feel stiff after doing many repetitive movements.

Static stretches reduce the stiff sensations in the short-term because they extend the nerves in the overworked tissues.

If runners want to do a small amount of static stretching and find that it helps them, it probably will not have a bad effect on performance or increase injury risk, he told Reuters Health by email.

But instead of doing mainly static stretching, it would be better for runners to do strength training exercises and "progress their running at a sensible rate to avoid injury."

I'm Alice Bryant.

Carolyn Crist reported this story for Reuters Health. Alice Bryant adapted it for Learning English. Caty Weaver was the editor.

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myth - n. an idea or story that is believed by many people but that is not true

warm-up - n. an exercise or set of exercises done to prepare for a sport or other activity

joint - n. a point where two bones meet in the body

infographic - n. a visual image such as a chart or diagram used to represent information or data

physiotherapist - n. a person qualified to treat disease, injury, or deformity by physical methods such as massage, heat treatment, and exercise

soreness - n. the pain and stiffness felt in muscles several hours to days after strenuous exercise

relax - v. to become or to cause something to become less tense, tight, or stiff

stress - n. physical force or pressure

shin splints - n. pain felt along the front of your lower leg, at the shin bone.

stiff - adj. painful or difficult to move or bend