Stretching relieves stiff muscles and can boost flexibility in the elderly and inactive, but experts are divided on how vital it is for general fitness and preventing injury.
For older adults who lose flexibility through aging, stretching can improve a range of motion and can make it easier to do everyday tasks such as reaching for items on high shelves.
Flexibility activities can also help reverse the chronically rounded shoulders and hands-on-keyboard posture of office workers tied to their desks.
But Dr. Mike Bracko, an exercise physiologist with the American College of Sports Medicine, said research indicates that static stretching, which involves holding a stretch for 30 to 60 seconds, does not reduce injury and actually makes the muscle weaker.
He said "I would say that flexibility in and of itself is not that important a component of general fitness".
Bracko, a hockey coach in Calgary, Alberta, notes that while activities such as gymnastics and rock climbing require flexibility, others, such as boot camp or cycling, do not.
"A lot of people just doing normal fitness activities don’t need a lot of flexibility. It depends on the person", he said, adding that muscles tend to get injured within the normal range of motion.
"The classic example is how sprinters strain hamstrings: The leg reaches forward, at some point hamstrings have to contract fast. That’s when the muscle fails", Bracko said, adding "stretching can’t deal with that".
But he said studies showed that dynamic stretching, which unlike static stretching is not sustained and mimics the activity to be performed, decreases the risk of injury by preparing the body for movement.
Stretch Zone Inc., which was founded in 2004, specializes in practitioner-assisted stretches that are activity-specific and dynamic.
"Nothing is held for more than two seconds", founder Jorden Gold said. "All the studies show little correlation between static, long-held stretches and sports performance".
The company includes stretches tailored to golfers, backpackers and officer workers, said Gold, whose clients range from the National Football League to musicians.
"With a sedentary lifestyle, the body picks up slack", he explained, adding "If, for example, I stretch hip flexors [which move muscles when running and walking], I’ll feel lighter because the body is not fighting itself". He also said that stretching could lengthen a muscle 1.6 times its resting length.
But Jessica Matthews, a California-based exercise physiologist formerly with the American Council on Exercise, said the science on stretching was still evolving.
She said "we all agree on a dynamic warm-up", noting "but research on stretching for injury prevention is still not conclusive enough to make that correlation. There isn’t clear-cut evidence to support one thing or another".
The American College of Sports Medicine recommends adults train for flexibility at least twice a week.