Lifting

• Lifting process is applied frequently by most of the people, so it’s very necessary to know the loads during lifting, include the weight of the load, the distance of the centre of gravity from the fulcrum of the spine, and the inclination of the trunk.

• The person should follow certain steps of proper lifting

• Factors affecting load on the spine during lifting

1- position of the object in relation to center of motion of the spine

The object must close to the body as much as possible . If the object is away from the spine that causes increase in the distance between the center of gravity of the object and the center of the motion of the spine . This will increase the bending moment and the load on the back muscles

2- degree of flexion and rotation of the spine Spine is more flexible in flexion than in extension . Increase

the amount of flexion of the spine will cause an increase in the bending moment created by the weight of the object and the weight of the upper body . This moment must be counterbalanced by another moment in the opposite direction created by the back muscles

So the activities of the back muscles increases and also the load on the intervertebral discs

• When the spine is flexed to 60 degrees, the activities of the back muscles increases to counterbalance the upper body weight however the angle of pull of the muscles is small and the moment arm of the muscles is also small . This will increase the demand on the back muscles .

• When the flexion of the spine is more than 60 degrees. The back muscles are inactive and the load is brought by the spinal ligaments so the forward bending moment is counterbalanced by

The ligaments . Because these ligaments have shorter lever arm than the muscles, so the load on the ligaments becomes extremely high in this position .

• In addition the elastic property of the ligaments are less than muscles so the ligament are more susceptible to injury in this position than muscles.

• If flexion of the spine is more than 60 degrees while the subject lift a heavy load in a sudden or jerky manner that leads to lumbar disc prolapsed

3- Characteristics of the object (this include size, weight, density and shape)

A - the size of the object : if the object is big , the lever arm produced by the size of the object increases and also the bending moment created by the object on the lumbar spine that lead to increase the moment created by the back muscles and the load on the intervertebral discs and also there is an increase in the intradiscal pressure

B- the weight of the object : If the weight of the object is heavy, the bending moment created by the weight of the object increases , that leads to increase the moment created by the back muscles and the load on the intervertebral discs and also there is an increase in the intradiscal pressure.

4- Role of the abdominal muscles and the intra -abdominal pressure during lifting

A- in case of strong abdominal muscles Strong abdominal muscles can create high intra-abdominal

pressure and high intra-thoracic pressure this has many advantages : it decrease load on the intervertebral discs during lifting and as a consequence , the load on the lumbar spine and it also increases the person capacities of lifting load . That appears clearly in athletes where the load on the lumbar spine decreases by 40 %

• The intra-abdominal pressure increases by increasing the weight lifted and also when the speed of the weight lifted is faster .

B- in case of weakness of the abdominal musclesThis will affect on intra-abdominal pressure and

activity of the back muscles , person with weak abdominal muscles can not create enough intra-abdominal pressure so the load will increase on the intervertebral discs during lifting .

• If the person tries to create high intra-abdominal pressure with weak abdominal muscles , this may lead to hernia.

• Weakness of the abdominal muscles causes belly abdomen which increases lever arm of the adipose tissue so the moment created anteriorly increase and also the moment created posterior by the activities of the back muscles increases to counterbalance the forward moment . The activities of erector spinae muscles increases the load on the interverebral disc and joint reaction force

N.B• patient with weakness of abdominal muscles

is advice to strengthen the abdominal ms rather than wear the abdominal corset which will lead to more weakness

Steps of proper lifting • There are five steps of proper lifting . Assuming

these steps while lifting will preserve energy and prevent any strains on the back and also will prevent any disease. These steps are :

1- the first step: facing correctly 2- the second step: assume natural lifting position3- the third step: lifting the load4- the forth step : turning properly5- the fifth step : putting the load down

The first stepfacing correctly

• Face the correct direction to prevent unnecessary turning while lifting

• Foot placement must be with wide base of support to increase the stability

• Friction between the foot and the ground should be present with a reasonable value to prevent slipping during lifting

The second stepassume natural lifting position

• Squat on knees to preserve energy and to decrease strain on lower limb joints

• Back should be straight as much as possible but not stiff: to decrease the lever arm of the body weight and decrease the bending moment that will decrease the strain on the lower back muscles and the load on the intervertebral discs. so the JRF decreases

• Keep the object close to the body as much as possible to- decrease leverage needed to lift the weight,- make combined COG of the object and the body over the

base of support- decrease bending moment created by the weight of the

upper body and the weight of the object . So the muscular activities needed and the energy expenditure will decrease

- Decrease the load on the intervertebral discs so the joint reaction force decreases

• Grip with all the hand and not with the tips of fingers to:

- Prevent undue pressure on certain areas of the lifter’s hands

- Counteract the downward pulling force of the weight

• Person can wear gloves in his hands to :- Protect his hands- Increase the friction between the object and

the lifter’s hand so that it prevents slipping during lifting or carrying.

The third step lifting the load

• The lifter should be sure to - Lift the object with the legs only and not with the

trunk that is because the legs ms are stronger than the back ms

- Lift smoothly and avoid jerky lifting or twisting to prevent strain or undue stress on the back and avoid an increasing in the load on the intervertebral discs

The forth step turning properly

• Take the load slowly as turning too quickly may lead to undue stress on the back and may cause injuries to the soft tissue structures.

• start turning with both feet and not with the

trunk . Then follow the movement with the trunk

The fifth stepputting the load down

• Put the load as pick it up• Make the leg muscles do the action

Steps of lifting from a shelf

• Stand stride with wide base of support. One foot in the front and the other on the back

• The weight of the body must be on the

forward leg

• As the object is lifted down , the weight is shifted to the backward leg to :

- prevent undue extension of the lumbar spine - Prevent strain on the lower back- Increase stability by increasing base of

support

Carrying a load • In order to preserve energy and decrease

muscular activities during carrying a load, the following items should be achieved :

1- carrying the load near to the body as much as possible to decrease strain on the back and preserve energy.

2- carrying the object on or at the shoulder level so as to make the COG of the object near the midline so the ms activities and energy expenditure will decrease.

3- carrying the object over the head to make the COG of the object and its line of gravity passes through the midline this will reduce the energy expenditures and ms activities to the minimum and will also prevent strain on the lumbar region but it is less common to carry a load on the head

Improper lifting • If the subject does not follow the steps of

proper lifting , the trunk and the discs will subjected to a large amount of stress and damage maybe occur. This include:

1- feet are closed together , this gives limited base of support and less stability

2- friction is small between surface and feet

3- hands does not contribute the upward force as in grasping with the tips of fingers

4- lifting by making extension of the trunk or making jerky lifting or twisting while lifting

5- turning too quick or turning with trunk rotation and fixed lower limbs

6- lifting with straight knees and flexion of trunk leads to :

A- increase bending moment which causes more pressure and more strain on the back structures

B- increase torque on the lumbar spine which increased by increasing degree of trunk flexion

C- as flexion of the of the back increases, the angle of pull of the back ms decreases . So the effective component of the muscle support the trunk becomes small.

According to length- tension relationship , the ms tension increases and the compressive force increase

Also