sage
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common exerises and potential for injuires....prevention
Technique 1: Latissimus Dorsi Pull-Down
Problem: When the weight is lowered behind the neck, this exercise excessively flexes the cervical spine and loads the shoulders at the extreme of external rotation. The line of pull does not oppose the muscle fibers of the latissimus dorsi, and this does not maximally challenge the muscle. The behind-the-neck position increases the load on the cervical disks and the risk of spinous process fracture. The exercise puts the shoulder at a mechanical disadvantage that may contribute to rotator cuff injury or anterior shoulder instability. An excessively wide grip on the bar should also be avoided because it may increase shear forces across the glenohumeral joint.
Solution: The safer way to perform the exercise is to sit or kneel on one knee, lean back slightly at the hips, grip the bar slightly wider than shoulder width, and pull it down in front of the head.
Another exercise that effectively challenges the latissimus dorsi is seated rowing, an activity that minimizes shear force at the shoulder.
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Technique 2: Knee Extension
Problem: Knee extensions are examples of open-kinetic-chain exercises, which isolate a particular muscle group--in this case, the quadriceps--and involve motion distal to the axis of the joint. During knee extensions, potentially damaging tibiofemoral shear forces are greater during the last 5¡Æ to 10¡Æ of extension and also if one "hyperextends" the knee. In addition, at the extremes of knee flexion (greater than 60¡Æ), increased patellar compression is potentially harmful (1,2).
Solution: Avoid "hyperextension" of the knee at the completion of knee extension, and train in a range that avoids extremes of knee flexion and extension, especially as the load is increased. Also, try to incorporate closed-kinetic-chain exercises, which involve predictable coordinated muscle contractions with motion at multiple joints in a limb whose segment meets fixed or constrained resistance.
Squats and leg presses can each be closed-kinetic-chain exercises, and shear force is generally less with these exercises, though a recent study (3) suggests that strain on the anterior cruciate ligament (ACL) is simmilar in both open- and closed-chain exercises.
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Technique 3: Bench Press and Chest Fly
Problem: Hyperextension of the shoulders during bench press or chest fly exercises (dropping the elbows below or behind the plane of the body) places the pectoralis muscles at a mechanical disadvantage, contributes to glenohumeral instability through repetitive shoulder capsule trauma, and places excessive traction on the acromioclavicular joints (4).
Solution: The preferred way to perform the exercises is to adjust the exercise machine or starting position so that the elbows are even with or above the frontal plane when beginning the lift and during repetitions.
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Technique 4: Military Press
Problem: Extreme shoulder external rotation and abduction during behind-the-neck military presses stress the shoulder capsule and inferior glenohumeral ligament, which can cause anterior shoulder instability (5,6). Extreme cervical flexion puts patients at risk for spinous process fracture and neck strains.
Solution: The safer way to do military presses is to lift the weight in front of the neck.
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Technique 5: Squats
Problem: In a deep squat, when the thighs are parallel to the floor or lower, there is an excessive amount of shear load on the knee in a position in which the articular cartilage is thinnest. Descending to this position is done by power lifters who must meet technical specifications during competition, but they also place themselves at risk of cartilage damage.
Solution: Weight lifters should avoid deep squats and extremes of hyperflexion and hyperextension, and they should maintain lumbar spine stability during squat lifts
Technique 1: Latissimus Dorsi Pull-Down
Problem: When the weight is lowered behind the neck, this exercise excessively flexes the cervical spine and loads the shoulders at the extreme of external rotation. The line of pull does not oppose the muscle fibers of the latissimus dorsi, and this does not maximally challenge the muscle. The behind-the-neck position increases the load on the cervical disks and the risk of spinous process fracture. The exercise puts the shoulder at a mechanical disadvantage that may contribute to rotator cuff injury or anterior shoulder instability. An excessively wide grip on the bar should also be avoided because it may increase shear forces across the glenohumeral joint.
Solution: The safer way to perform the exercise is to sit or kneel on one knee, lean back slightly at the hips, grip the bar slightly wider than shoulder width, and pull it down in front of the head.
Another exercise that effectively challenges the latissimus dorsi is seated rowing, an activity that minimizes shear force at the shoulder.
--------------------------------------------------------------------------------
Technique 2: Knee Extension
Problem: Knee extensions are examples of open-kinetic-chain exercises, which isolate a particular muscle group--in this case, the quadriceps--and involve motion distal to the axis of the joint. During knee extensions, potentially damaging tibiofemoral shear forces are greater during the last 5¡Æ to 10¡Æ of extension and also if one "hyperextends" the knee. In addition, at the extremes of knee flexion (greater than 60¡Æ), increased patellar compression is potentially harmful (1,2).
Solution: Avoid "hyperextension" of the knee at the completion of knee extension, and train in a range that avoids extremes of knee flexion and extension, especially as the load is increased. Also, try to incorporate closed-kinetic-chain exercises, which involve predictable coordinated muscle contractions with motion at multiple joints in a limb whose segment meets fixed or constrained resistance.
Squats and leg presses can each be closed-kinetic-chain exercises, and shear force is generally less with these exercises, though a recent study (3) suggests that strain on the anterior cruciate ligament (ACL) is simmilar in both open- and closed-chain exercises.
--------------------------------------------------------------------------------
Technique 3: Bench Press and Chest Fly
Problem: Hyperextension of the shoulders during bench press or chest fly exercises (dropping the elbows below or behind the plane of the body) places the pectoralis muscles at a mechanical disadvantage, contributes to glenohumeral instability through repetitive shoulder capsule trauma, and places excessive traction on the acromioclavicular joints (4).
Solution: The preferred way to perform the exercises is to adjust the exercise machine or starting position so that the elbows are even with or above the frontal plane when beginning the lift and during repetitions.
--------------------------------------------------------------------------------
Technique 4: Military Press
Problem: Extreme shoulder external rotation and abduction during behind-the-neck military presses stress the shoulder capsule and inferior glenohumeral ligament, which can cause anterior shoulder instability (5,6). Extreme cervical flexion puts patients at risk for spinous process fracture and neck strains.
Solution: The safer way to do military presses is to lift the weight in front of the neck.
--------------------------------------------------------------------------------
Technique 5: Squats
Problem: In a deep squat, when the thighs are parallel to the floor or lower, there is an excessive amount of shear load on the knee in a position in which the articular cartilage is thinnest. Descending to this position is done by power lifters who must meet technical specifications during competition, but they also place themselves at risk of cartilage damage.
Solution: Weight lifters should avoid deep squats and extremes of hyperflexion and hyperextension, and they should maintain lumbar spine stability during squat lifts
