We have always been told that stretching is as essential to a workout as a pair of trainers and a water bottle. Sedentary lifestyles mean our range of movement is restricted and the resulting lack of flexibility is responsible for an increase in back, neck and postural imbalances. Indeed, for people intent on achieving a toned and supremely functional body, a stretch therapist can be added to the personal trainer, osteopath and chiropractor, physiotherapist, nutritionist and masseur. Yet as the popularity of stretching has soared, so has the number of scientific experts questioning its merits.
Its proponents say stretching is the only way to enhance flexibility, which thereby can boost circulation, fill your muscles with oxygen and flush out waste products that can leave you tired, stiff and sore. It sounds like an antidote to modern living that few of us should do without. "There is little doubt that stretching is an important part of a workout regimen," says James Cloke, a personal trainer with FitnessO2 in Dubai. "When you exercise or sit at your desk, your muscles contract, which makes the length of them get shorter and longer. If they are not stretched back to their natural length it can lead to problems."
But is the kind of extreme flexibility currently being touted in fitness classes and by trainers really the cure-all for everyday aches, pains and strains that we are led to believe? A growing number of experts think not. According to the American Council on Exercise, an independent watchdog on fitness issues, most people need only maintain the normal range of motion to function safely. Too many people, however, don't stop there.
"There is a general assumption that if being able to touch your toes is considered good, then being able to touch 8cm past your toes must mean you are fitter and healthier," says Louise Sutton, head of the Carnegie Centre for Sports Performance and Wellbeing at Leeds Metropolitan University in the UK. "But there is plenty of research showing that, actually, hypermobility - or being too flexible - can be a risk factor for injury."
Claire Small, a spokeswoman for the Chartered Society of Physiotherapists, says that inflexibility means a joint becomes compressed because it is not properly lubricated. But she agrees that being too flexible "is as much a risk factor for injury as being too stiff". Where people often make a mistake, she says, is overstretching one muscle while neglecting others. "If a middle joint is stiff, those above it and below will move around too much," she says. "The key to a good stretching programme is to balance out your approach so that all muscles and joints are worked on."
Others claim there is a misperception that stretching, especially before a workout, will help to reduce the risk of injury. "Unfortunately, the evidence on this front is, at best, debatable," says Sutton. "In fact, poor stretching can lead to decreased muscle function which means you do a less effective workout or training session." Surprisingly, it is the belief that static stretching - the kind that involves holding a position for several seconds - primes muscles for activity that has been proved wrong. Many studies have shown that pre-workout static stretches do nothing to improve the body's readiness for exercise and may leave muscles weaker.
When Dr Ian Shrier, of the Centre for Epidemiology at the Jewish General Hospital in Montreal, reviewed the evidence on pre-workout stretching for The Physician and Sportsmedicine journal a few years ago, he found that stretching immediately before a gym session led to a reduction in muscle power. The effects were small and temporary, but for anyone needing to perform kicks or jumps (in football or martial arts) or who wants to lift weights, this could be limiting.
As a result of his findings, Shrier, a past president of the Canadian Academy of Sport Medicine, recommends dropping stretches from warm-ups. "Ideally, stretching should be done after exercise or at a time not related to your main workout," he says. Other researchers have since confirmed his findings, some saying that stretching cuts muscle strength by up to 30 per cent. Meanwhile, in an investigation at the University of Nevada the use of stretches to limit injury was shown to have the opposite effect for some people. Whereas previous studies had looked at stretching for eight to 10 minutes as part of a serious athletic warm-up, the team from Nevada looked at the effects of the average 90 seconds of stretching on the quadriceps and hamstring muscles performed by gym-goers. Results, published in the Journal of Strength and Conditioning Research, showed that even this small amount of stretching placed exercisers at a disadvantage by reducing power, strength and overall performance.
In spite of this glut of negative evidence, experts are keen to emphasise that stretching can still play a role in good health. That role is just more limited than once thought. Sutton says, for instance, that regular teasing of the joints as a result of stretching may lead to improved joint-position feedback mechanisms, otherwise known as muscle proprioception, which are essential for good balance and co-ordination.
Experts also now think that dynamic stretching movements such as arm-circling and sidestepping - the type we used to be told to avoid - can boost power, flexibility and range of motion. Instead of producing the kind of inhibitory response from the muscles that static stretching triggers, dynamic movements send a message from the muscles to the brain indicating that they are ready to work out. "There is great advantage in dynamic stretching prior to a tough training session or competitive sport," says Cloke. "Highly dynamic stretches are basically a rehearsal of the actual movement someone will be performing in a workout proper and prepare the muscles specifically for what they are about to experience."
A study published last year by the Centres for Disease Control in the US showed that the number of knee injuries among female footballers was cut by half when they followed a football-specific warm-up that included dynamic stretches. So is it better to stretch after a workout? Yes, say Cloke and other experts, but probably not for the reasons you might expect. It is a popular misconception that cooldown stretches will stop muscles from becoming sore by flushing out lactic acid, the waste product of exercise. "But soreness is a result of minor damage to fibres and it is not caused by lactic acid, so no amount of stretching will boost post-workout fatigue and soreness," Sutton says.
Indeed, a South African study of adults who had been asked to walk backwards on a treadmill for half an hour to cause calf-muscle stiffness found that those who did a 10minute cool-down had no less soreness afterwards than those who did not. A cool-down is important as it is widely accepted that intense exercise should never be stopped abruptly. When you work out hard, the heart pumps faster and blood vessels expand to promote blood flow to the legs and feet. Stopping too suddenly can cause blood to pool in the lower limbs, causing dizziness. But a gentle jog or walk is the best way to wind down from exercise and the only advantage to stretching immediately after vigorous activity is that the muscles and body are warm.
Ultimately, say the experts, the goal of stretching should be to counteract normal stiffness and ensure a full range of motion, making day-to-day activities easier. And that, says Cloke, means that light stretching most days is enough to maintain or improve muscle and joint mobility. "For example; if you have tight pectorals or chest muscles caused by hunching at a desk, it can lead to your shoulders becoming rounded and give you an exaggerated curve in the thoracic spine," he explains. "But regular stretching can counteract problems like this."
By far the best time to stretch is at the end of the day when the muscles are warm and the joints well lubricated. "Your muscles have been on the move all day," says Sutton. "Stretching will help you to relax, unwind and get a good night's sleep."