New Scientist  18 December 1999
	Skip the warm-up
	Don't bother with the stretches ... you'll pull a muscle anyway
	STRETCHING before you exercise in a bid to prevent injuries is a waste of time.  So say Australian researchers who have advised the country's army to consign the tradition to the scrap heap.
	Army physiotherapist Rod Pope, working with colleagues at the University of Sydney and Charles Sturt University has monitored more than 2600 army recruits over a year in randomised, controlled trials.  Some of the recruits stretched particular leg muscles before exercise; others did not.  Yet there were no differences in injury rates between the two groups-and not just because too few recruits in either group became injured to register a significant effect.  "We were able to rule out even a quite small effect of stretching," says Pope.  "This has not been properly researched before," he explains.  "Stretching was assumed to work in preventing injury, but there was no evidence to suggest it did."
	The work has been accepted for publication by Medicine and Science in Sports and Exercise, the journal of the American College of Sports Medicine.  "We are telling the army to no longer stretch," says Pope.  "But it's a long tradition and tradition dies hard.'
	Despite this advice, Pope stresses that it is important to stretch muscles which are tight and could restrict the normal range of movement.  He also suspects that stretching after exercise could be beneficial - although this has not been fully investigated.  "There is no evidence that points unequivocally one way or the other," says Robert Price of Deakin University in Melbourne. Julia Hinde, Melbourne
	and from The Physiology of Exercise
	A common behaviour observed in students and athletes prior to yoga classes, physical education classes, athletic practices, and sports competitions is the participants' actively "warming up" by stretching, performing callisthenics, jogging, and/or practicing the skills in which they are about to participate.  The traditional reasons given for this "warm-up' include the factors related to heat application described in the previous section. plus a desire to "loosen up" the muscles, tendons, and ligaments so that there will be less chance of injury to these tissues.  Another reason given in the late 70’s was that without warm-up, there is a greater possibility that blood flow to the heart muscle might be inadequate during the first seconds of all-out physical activity.
	It is unlikely that warm-up activities that increase body temperature substantially are 'beneficial to performance lasting more than a few minutes because the increased body temperature causes a shift of blood flow away from working muscles to the skin. Body metabolism is such that once energy is activated the body tries to cool such areas by increased circulation ~ with experiments artificially inducing heat, the muscle tissue rapidly cools within 2-3minutes,  There are, however some reports of a beneficial effect of warm-up in strength and sprint events, which can be performed with little blood flow to the working muscles because of the emphasis on anaerobic ATP production for such activities.  Such a positive effect of warm-up on athletic performance is quite difficult to demonstrate: about 50% of the available studies have reported that warm-ups was either ineffective or in a few cases, was actually harmful to performance.  Any beneficial effect of warm-up is small and can be easily obscured by differences in motivation, pain tolerance, techniques of performance, and strategy.
	The facts that (1) there is no overwhelming evidence that warm-up is advantageous to performance, and (2) there is no scientific evidence that athletes are less apt to suffer injury after warm-up do not mean that warm-up practices should be discouraged.  There is some evidence that warm-up is harmful to performance, and the personal empirical experience of thousands of athletes and coaches suggests that warm-up does help prevent injuries.  Accordingly, warm-up practices should be promoted with greatest use being, made of practice of the actual physical activist in which the exerciser is about to participate.  Supposedly, these preliminary trials will help to establish the appropriate neural patterns for the final performance of the activity.  There is some evidence that it may be useful to those who are about to participate in very heavy exercise that places sudden demands on the heart and circulation.  The warm-up should minimize the risk of inadequate coronary blood flow during the first few seconds of heavy exercise.
	Sources:
	(1) Skubic.V & J Hodgkins.    Effect of warm-ups on speed strength and accuracy. Res Q 28  147-152.
	(2) Karpvitch and Hale.  Effect of Warm-up on performance JAMA 162  1117-11194.
	(3) Franks. B.D.....p 160-191.   Ergogenic Aids and Muscular Performance. Academic Press 1992 .
	(4) Asmussen E.   Body Temperature and work. Acta.Physiol Scand. 10 ...1-22.
	(5) Bergh.U.     Physical performance at different body temperatures. Appl. Physiol. 46 885-889.
	From health page The Times 18th April 2002
	Article by Colin Cottell
	Stretching and Exercises
	Stretch before you exercise  has long been the mantra of the virtuous exerciser, convinced of the health benefits of the muscle warm-up. It is widely believed that runners, for instance, who stretch their calves and hamstrings before running not only reduce muscle soreness, but by increasing their flexibility they also lower their chances of getting injured.
	However, a paper recently published in the British Medical Journal (BMJ) has raised questions about the need to stretch before exercise. When physiotherapists at the University of Sydney looked at studies of military recruits, they found that although stretching resulted in a 5 per cent decrease in the risk of injury, this was so small as to be practically meaningless.
	According to Dean Kenneally, chief physiotherapist at UK Athletics, coaches and athletes are re-thinking the value of stretching after the paper's publication. But others have taken immediate action. At Reading Roadrunners the warm-up no longer includes static stretching, says the club coach, Tony Brown ("static" means stretching the muscle to the point of resistance and holding it for a period of time).
	So is static stretching before exercise a waste of time? Rachel Stanley, a London-based 'chartered physiotherapist specialising in sports injuries* suggests that stretching is best done after a workout "Your temperature is raised after exercise, so you-get increased extensibility in the tissues, ligaments, tendons, muscles and neural structures," she says. And with a greater range of movement, comes increased mobility, reducing the chances of injury.
	This ties in with findings by David Lally, an exercise physiologist, who, in a study of marathon runners in the 1990s, found that over a one-year period male runners who stretched after running were less likely to get injured than those who stretched before, or not at all.
	Dr Ralph Rogers, medical director at the Most sports clinic in Birmingham, agrees with Stanley that static stretching is most beneficial once the body's temperature has been raised. However, he says, this doesn't necessarily mean waiting until you have finished your exercise session. Five to ten minutes of static stretching as the second stage in a warm-up process 9perhaps after a jog) can be of benefit, he says. Having warm muscles increases the range of movement so you don’t pull.
	Other experts, such as Dr Anthony Blazevich, a lecturer in biomechanics at Brunel University, believe that there is a role for pre-exercise static stretching. He compares the muscles to a rubber band, which will break if stretched beyond its limits. "Make sure that your rubber band is long enough. Stretching it even once can increase its length," he says. However, to minimise the chances of injury, the degree of flexibility practised during stretching will need to be slightly greater than that required for the exercise activity. "See a physiotherapist to help you design a suitable programme, where muscles are tight there can be a need for static stretching beforehand to prevent injury," he says.
	He offers the example of a bench press. "If the shoulders and chest are very tight, the muscles are going to be under strain early in the routine, and therefore you are more likely to get injured. Light stretching increases the range of motion [degree of flexibility] around a joint, and this means that injury is less likely."
	He says, one possible downside to stretching after exercise is that it can exacerbate micro-tears in muscle tissues caused by the exercise. While opinion differs on the merits of pre- and post-exercise static stretching, most experts agree that, done correctly and gently, static stretching is not harmful. "A light static stretch is unlikely to cause injury," Blazevich says.
	He points to several studies showing that lots of stretching made muscles weaker, reduced performance and increased injury risk. As Rogers  confirms: "Static stretching for an hour cannot be good for the muscle."
	So with all these shades of opinion, what should you be doing when you're next at the gym? According to Kenneally, it is "about making decisions on an individual basis and coming to a balanced view - there is no right or wrong". In the end it may come down to common sense, Rogers says. "Certain things are obvious. No one can tell me that if you go from sitting in a chair into hard exercise without stretching you won't pull a muscle."

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