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ישן 18-02-07, 22:41   #1
igorek
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תאריך הצטרפות: Apr 2006
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ברירת מחדל שימוש בחגורות - דר. סטוארט מקגיל (כתבה באנגלית)

דר. סטוארט מקגיל נחשב לאחד מבכירי חוקרי בריאות עמוד בשידרה בעולם. הנה מה הוא חושב על חגורות:
ציטוט:
On The Use of Weight Belts
By Stuart M. McGill, Professor of Spine Biomechanics, University of Waterloo, Canada

A review invited by the National Strength and Conditioning Association
March 2005, Revised Sept 05

Scientific studies regarding the use of belts for athletic endeavours is scarce. Much more evidence and insight exists for the use of belts in occupational settings. The relevant information from occupational usage is discussed in this article and is blended with the limited work on athletic/performance use to form a position statement. Given the assets and liabilities of belt wearing, they are not recommended for healthy individuals either in routine work or exercise participation. However, the temporary prescription of belts may help some individual workers return to work. The exception is for extreme athletic lifting where belts appear to increase torso stability to reduce the risk of buckling and provide some elastic extensor recoil to assist with the lift. But the possible liabilities underscore the counterpoint to this proposition. The individual must make their own informed decisions on whether or not to wear a belt although guidance is provided here for their prescription and use.

The average person must be confused when they observe both Olympic lifters and back-injured people wearing back belts. A review of the documented effects of belt wearing in occupational settings (McGill, 1993) would support that:

• Those who have never had a previous back injury appear to have no additional protective benefit from wearing a belt.
• Those who are injured while wearing a belt seem to risk a more severe injury.
• Belts appear to give people the perception they can lift more and may in fact enable them to lift more.
• Belts appear to increase intra-abdominal pressure and blood pressure.
• Belts appear to change the lifting styles of some people to either decrease the loads on the spine or increase the loads on the spine.

Other opinions have been expressed regarding the mechanisms of belts, although few hold up to scrutiny. For example, some have suggested that belts perform the following functions:

• Remind people to lift properly
• Support shear loading on the spine that results from the effect of gravity acting on the handheld load and mass of the upper body when the trunk is flexed
• Reduce compressive loading of the lumbar spine through the hydraulic action of increased intra-abdominal pressure associated with belt wearing
• Act as a splint on the torso, reducing the range of motion and thereby decreasing the risk of injury
• Provide warmth to the lumbar region
• Enhance proprioception via pressure to increase the perception of stability
• Reduce muscular fatigue
• Provide stiffening to the torso to enhance performance

Many of these remain contentious.

The Recreational/Occupational Use of Belts

While there are guidelines for belt wearing for occupational use, sporting use requires a different approach. Occupational use is based on the premise of injury risk reduction while sporting use includes performance enhancement – to lift more for example. Previous recommendations for occupational use (see McGill, 1993, 1999, 2004) presented data and evidence that neither completely supported, nor condemned, the wearing of abdominal/back belts. Given the available literature, it would appear that the universal prescription of belts (i.e., providing belts to all workers in an industrial operation) is not in the best interest of globally reducing the risk of injury. Uninjured workers do not appear to enjoy any additional benefit from belt wearing, and in fact may be exposing themselves to the risk of a more severe injury if they were to become injured. Moreover, they may have to confront the problem of weaning themselves from the belt. However, if some individual workers perceive a benefit from belt wearing, they may be allowed to wear a belt conditionally, but only on trial. Having considered the scientific evidence for belt wearing for occupational and athletic use that the mandatory conditions for occupational/recreational prescription (for which there should be no exception) are as follows:

1. Given the concerns regarding increased blood pressure and heart rate and issues of liability, all candidates for belt wearing should be screened for cardiovascular risk by medical personnel.
2. Given the concern that belt wearing may provide a false sense of security, belt wearers must receive education on lifting mechanics. All too often, belts are being promoted as a quick fix to the injury problem. Promotion of belts, conducted in this way, is detrimental to the goal of reducing injury as it redirects the focus from the cause of the injury. Education programs should include information on how tissues become injured, techniques to spare the back, and what to do about feelings of discomfort to avoid disabling injury.
3. Consultants should not prescribe belts until they have conducted a full ergonomic assessment of the individual’s job, or a very thorough analysis of their training/lifting technique. Belts are no substitute for poor lifting technique. The ergonomic approach should examine, and attempt to correct, the cause of the musculoskeletal overload and provide solutions to reduce the excessive loads.
4. Belts should not be considered for long-term use. The objective of any small-scale belt program should be to wean workers from the belts by insisting on mandatory participation in comprehensive fitness programs and education on lifting mechanics, combined with ergonomic assessment. Furthermore, consultants would be wise to continue vigilance in monitoring former belt wearers for a period of time following belt wearing, given that this period appears to be characterized by an elevated risk of injury.
5. An analysis of the anatomy and biomechanics of the torso shows that there is a natural belt formed by the abdominal wall and the lumbodorsal fascia. Training the core musculature enhances the stabilizing effect of the “natural belt” by both strengthening the core and improving the motor control of these muscles so that they work as a team to enhance back stability.

Belt use for Serious Lifting Athletes

Much of the occupational evidence has relevance for athletic use of belts. There is no question that belts assist in generating a few more Newton-meters (or foot-pounds) of torque in the torso through elastic recoil of a bent torso that is stiffened with a belt. However, if a neutral spine is preserved throughout the lift this effect is diminished. In other words, to obtain the maximal effect from a belt, the lifter must lift poorly and in a way that exposed the back to a much higher risk of injury! There is no question that belts assist in generating torso stiffness to reduce the risk of spine buckling in extreme heavy lifts. Many athletes working at this edge of the envelope will receive this assist. However, other techniques are employed to maximize the torso stiffness – the lungs are filled to almost the top of tidal volume and the breath is then held. In some tasks, an athlete will only “sip” the air never allowing much air to leave the lungs that would reduce torso stiffness. Belts also increase intra-abdominal pressure which in turn increases the CNS fluid pressure in the spine and, in turn, the brain. This decreases the transmural gradient (the pressure difference between the arterial blood pressure in the brain vessels and the brain itself) which in turn may reduce the risk of aneurysm, or stroke. Others have argued that this effect has detrimental implications for venous return to the heart. There appears to be no evidence to suggest where the balance lies on this issue. There are other counter considerations. Evidence suggests that people change their motor patterns, together with their motion patterns when using a belt. The evidence suggests that these motor control changes can elevate the risk of injury should a belt not be worn in a belt-training athlete. The severity of a back injury may be greater if a belt is worn.
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