Stretching immediately before sport may hinder rather than boost performance, according to research.
Athletes stretch as part of their warm up
Dr Ian Shrier of the SMBD-Jewish General Hospital in Montreal looked at 23 published studies.
In the Clinical Journal of Sports Medicine, he advocated regular stretching after exercise or at times unrelated to activity.
But UK sports injury expert John Brewer said people should continue to stretch before exercise.
Rather than assessing performance in actual athletic events, Dr Shrier looked at studies that had examined the effects of stretching in specific tests related to sports performance.
These included things like muscle force, torque and jumping height.
Nearly all of the 23 studies he looked at found stretching immediately before the tests reduced performance.
In comparison, seven studies of stretching on a regular basis found it improved performance in tests of muscle force and speed or velocity, with none finding it impaired performance.
Dr Shrier said acute stretching did not appear to improve sport performance and might even reduce it by causing muscle damage.
"If one stretches, one should stretch after exercise or at a time not related to exercise," he said.
But John Brewer, head of sports science at Lilleshall Sports Injury and Human Performance Centre in Shropshire, said: "It would be wrong to suggest that people should stop stretching before exercise because the evidence that it does harm is very limited."
He said it was good to stretch before doing sport because it increases the elasticity of the muscles, tendons and ligaments that will be used in vigorous exercise, thereby reducing the risk of injury.
"As long as they stretch sensibly and not too vigorously and warm the body up first with five to 10 minutes of light exercise like gentle jogging. People who overstretch can cause muscle damage."
He said as well as stretching before exercise it was important to incorporate regular stretches into training programmes to improve flexibility and performance.
"A big mistake that many people in sport make is that they are only doing their stretches when it's part of their warm-up," he said.
"It's important to do both. It can be done in your own bedroom or your own living room, 10 to 15 minutes every morning."
He said the research was interesting but that it did not reflect real-life sporting practices.
"It's not like getting out there and sprinting 100 metres or playing a game of football," he said.