Document ZBOGdNxrXOoy4LmY1odE4ZDLZ

24--Materials Handling and Storage the normal curvatures are maintained This normally curved spine is termed a "straight back '' With "straight back lifting" the spine is fairly ngid (nonmedically speaking) and the pressure on the lumbar intervertebral disks is evenly distributed When lifting with the back bent, the spine forms an arc with the re sult that the lower back muscles are subject to strain and there is uneven pressure on the disks In addition to the risk of intervertebial disk lesions, lifting an object with the back bent and the legs straight imposes excessive stress on the muscles of the back for two reasons First, the back must be inclined at a greater angle to the vertical for the hands to reach the object Since the "effective weight" (of the object plus the upper part of the worker's body) increases rapidly as this angle is in creased, a much greater effort is required to raise the back to its vertical position Second, muscular effort is required to "straighten" the spine When a weight is being lifted from the ground, making maximum effective use of the legs, the back is straight but inclined for wards As the lift proceeds by the extension of the knees, the back returns to the vertical position The position of the feet and the flexion of the knees are the key factors for maintaining a straight back Arms close to the body When lifting and carrying weights, the arms should be close into the body and remain straight whenever possible This is because flexing the elbows and raising the shoulders imposes unnecessaiy strain on the muscles of the upper arms and chest Carrying involves a static posture of the arms, and particularly m the case of long distances, any assistance given by the body in supporting the weight will lessen the tension m the muscles Carrying with the aims straight enables the weight to rest against the thighs Correct hold. An insecure grip may be due to taking the load on the finger tips, thus creating undue pressure at the ends of the digits and strain to certain muscles and ten dons of the arm Greasy surfaces often pre vent a secure hold--whenever possible such surfaces should be wiped clean The use of suitable gloves should also be considered A full palm grip will reduce local muscle stress in the arms and decrease the possibility of the weight slipping Chin in. Raising the top of the head and tucking the chin in straightens the whole spine, not merely the neck This automat ically raises the chest and conditions the shoul ders for more efficient arm action See illus trations on previous page This chin-in action should be introduced immediately before lifting and maintained throughout the movement The worker will be looking down at the early stages of the lift and this may conflict with his desire to raise his head to see where he is going However, as he returns to the upright position, his head will automatically be laised at the same time Use of bodyweight. With the correct posi tioning of the feet and the flexion and ex tension of the knees, the weight of the body can be effectively utilized to push and pull objects and to initiate a forward movement such as placing an object on a shelf or walk ing When lifting an object from the ground, the thrust from the back foot, combined with the extension of the knee joints, will move the body forwards and upwards and for a brief period it will be off balance This is immedi ately countered by bringing the back leg forward, as in walking, but by this time the lift is completed This forward movement of the body results m a smooth transition from lifting to carrying Here are some techniques for specific situa tions 1 If the object is too large or too heavy to be handled by one person, he should get help 2 Before lifting the load to be earned, the worker should consider the distance to be tiaveled and the length of time he will have to maintain the gnp He should recognize the fact that his gripping power may tire if he has to carry the load a long distance, especially if he bas to climb stairs or ramps 636