B ody mechanics means using the body in an efficient and careful way. It involves good posture, balance, and using your strongest and largest muscles for work. Fatigue, muscle strain, and injury can result from the improper use and positioning of the body during activity or rest. Focus on the person’s and your own body mechanics. Good body mechanics reduce the risk of injury.

See Body Structure and Function Review: The Musculo-Skeletal System.

Body Structure and Function Review

The Musculo-Skeletal System

The musculo-skeletal system:

• Provides the framework for the body.

• Lets the body move.

• Protects internal organs.

• Gives the body shape.

Bones

Bones are hard, rigid structures. They are made up of living cells. The human body has 206 bones.

• Long bones bear the body’s weight. Leg bones are long bones.

• Short bones allow skill and ease in movement. Bones in the wrists, fingers, ankles, and toes are short bones.

• Flat bones protect the organs. They include the ribs, skull, pelvic bones, and shoulder blades.

• Irregular bones are the vertebrae in the spinal column. They allow various degrees of movement and flexibility.

Joints

A joint is the point at which 2 or more bones meet. Joints allow movement. There are 3 major types of joints (Fig. 17-1).

• A ball-and-socket joint allows movement in all directions. It is made of the rounded end of 1 bone and the hollow end of another bone. The rounded end of 1 fits into the hollow end of the other. The joints of the hips and shoulders are ball-and-socket joints.

• A hinge joint allows movement in 1 direction. The elbow is a hinge joint.

• A pivot joint allows turning from side to side. A pivot joint connects the skull to the spine.

Some joints are immovable. They connect the bones of the skull.

Muscles

The human body has more than 500 muscles (Fig. 17-2, p. 252).

• Voluntary muscles can be consciously controlled. Muscles attached to bones (skeletal muscles) are voluntary. Arm muscles do not work unless you move your arm; likewise for leg muscles. Skeletal muscles are striated. That is, they look striped or streaked.

• Involuntary muscles work automatically. You cannot control them. They control the action of the stomach, intestines, blood vessels, and other body organs. Involuntary muscles also are called smooth muscles. They look smooth, not streaked or striped.

• Cardiac muscle is in the heart. It is an involuntary muscle. However, it appears striated like skeletal muscle.

FIGURE 17-2 A, Anterior view of the muscles of the body. B, Posterior view of the muscles of the body. (From Herlihy B, Maebius NK: The human body in health and illness, ed 4, St Louis, 2011, Elsevier.)

Muscles have 3 functions.

• Movement of body parts

• Maintenance of posture or muscle tone

• Production of body heat

Some muscles constantly contract to maintain the body’s posture. When muscles contract, they burn food for energy. Heat is produced. The more muscle activity, the greater the amount of heat produced.

Principles of Body Mechanics

Body alignment (posture) is the way the head, trunk, arms, and legs are aligned with one another. Good alignment lets the body move and function with strength and efficiency. Standing, sitting, and lying down require good alignment.

Base of support is the area on which an object rests. A good base of support is needed for balance (Fig. 17-3, p. 252). When standing, your feet are your base of support. Stand with your feet apart for a wider base of support and more balance.

FIGURE 17-3 A, Anterior (front) view of an adult in good body alignment. The feet are apart for a wide base of support. B, Lateral (side) view of an adult with good posture and alignment.

Your strongest and largest muscles are in your shoulders, upper arms, hips, and thighs. Use these muscles to handle and move persons and heavy objects. Otherwise, you place strain and exertion on the smaller and weaker muscles. This causes fatigue and injury. Back injuries are a major risk. For good body mechanics:

• Bend your knees and squat to lift a heavy object (Fig. 17-4, p. 252). Do not bend from your waist. Bending from your waist places strain on small back muscles.

FIGURE 17-4 Picking up a box using good body mechanics.

• Hold items close to your body and base of support (see Fig. 17-4). This involves upper arm and shoulder muscles. Holding objects away from your body places strain on small muscles in your lower arms.

Rules for Body Mechanics

All activities require good body mechanics. You must safely and efficiently handle and move persons and heavy objects. Follow the rules in Box 17-1.

Box 17-1

Rules for Body Mechanics

• Keep your body in good alignment with a wide base of support. Your feet are at least 12 inches apart or shoulder-wide apart.

• Use an upright working posture. Bend your legs. Do not bend your back.

• Use the stronger and larger muscles in your shoulders, upper arms, thighs, and hips.

• Keep objects close to your body when you lift, move, or carry them (see Fig. 17-4).

• Avoid unnecessary bending and reaching. Raise the bed so it is close to your waist. Adjust the over-bed table to your waist level.

• Face your work area. This prevents unnecessary twisting.

• Push, slide, or pull heavy objects when you can rather than lifting them. Pushing is easier than pulling.

• Widen your base of support to push or pull. Move your front leg forward when pushing. Move your leg back when pulling (Fig. 17-5).

FIGURE 17-5 Move your rear leg back when pulling.

• Use both hands and arms to lift, move, or carry objects.

• Turn your whole body when changing the direction of the turn. Do not twist your body.

• Work with smooth and even movements. Avoid sudden or jerky motions.

• Do not lean over a person to give care.

• Get help from a co-worker to move heavy objects. Do not lift or move them by yourself.

• Bend your hips and knees to lift heavy objects from the floor (see Fig. 17-4). Straighten your back as the object reaches thigh level. Your leg and thigh muscles work to raise the item off the floor and to waist level.

• Do not lift objects higher than chest level. Do not lift above your shoulders. Use a step stool or ladder to reach an object higher than chest level.

Work-Related Injuries

Work-related musculo-skeletal disorders (MSDs) are injuries and disorders of the muscles, tendons, ligaments, joints, and cartilage. They are caused or made worse by the work setting. They can involve the nervous system. The arms and back are often affected. So are the hands, fingers, neck, wrists, legs, and shoulders. MSDs are painful and disabling. They can develop slowly over weeks, months, and years. Or they can occur from 1 event. Pain, numbness, tingling, stiff joints, difficulty moving, and muscle loss can occur. Sometimes there is paralysis.

Early signs and symptoms include pain, limited joint movement, or soft tissue swelling. Time off work is often needed.

MSD Risk Factors

The Occupational Safety and Health Administration (OSHA) has identified MSD risk factors for the nursing team. An MSD is more likely if risk factors are combined. For example, a task involves both force and repeating actions.