The Musculoskeletal System (Structure and Function) (Nursing) Part 6

Muscle Tone

Because human beings stand erect against gravity’s constant pull, many muscles are constantly in a mild state of contraction, to help maintain balance. These are slow-twitch muscles. Even relaxed muscles are ready to go into action if they are in good condition. This state of slight contraction and the ability to spring into action is called muscle tone (tonus). Physical exercise improves muscle tone and increases muscle size. An idle muscle loses its tone and wastes away. If a person does not use muscles or uses them very little, they become flabby and weak (atonic) and may atrophy (waste away).

Special Considerations :LIFESPAN

Retaining Muscle Tone

Children who sit in school all day need to have an opportunity for vigorous play after school. Their bodies need such stimulation to build and maintain muscle tone.

Inactivity and pressure on nerves in muscles causes pain. People who must remain in bed require frequent repositioning. A back rub can be comforting and the client may require support when getting out of bed.

Nursing Alert A client who must remain in bed for any length of time should be positioned as if he or she were standing. If this position is not ensured, the muscles may become contracted because of an abnormal position (resulting in a contracture).

EXERCISE

Isometric and Isotonic Contractions

In addition to the constant muscle contractions of muscle tone, two other types of contractions are important. Isometric contractions do not increase the length of a muscle, but do increase muscle tension. For example, if you push against an unmovable object or tense the muscles in your upper arm, your muscles tighten. This is an isometric contraction or exercise. Bedridden clients are encouraged to do isometric exercises, even if they cannot be out of bed. Isotonic contractions shorten and thicken the muscle, causing movement. Exercises such as swimming, jogging, or bicycling are examples of isotonic exercises. A person in bed also can move the extremities and move about in bed to exercise the muscles. It is important to vary the exercise program; different exercises use different muscles.


Aerobic and Anaerobic Exercise

Aerobic exercise (using oxygen) involves a long period of less than maximum exertion. Muscles are used for a longer time, but not maximally contracted. These exercises use a greater percentage of slow-twitch muscles; fat, carbohydrate, and protein are all used for energy. In addition, a great deal of oxygen is used and very little, if any, lactic acid is produced. Running a marathon is an aerobic exercise.

In anaerobic exercise (without oxygen), mostly fast-twitch muscle fibers are used, at close to maximum contraction strength. In this case, ATP and glucose are the main energy sources, little oxygen is used, and a great deal of lactic acid is produced. The lactic acid inhibits ATP production. As a result, anaerobic exercise cannot be sustained for a long time. Examples include fast sprints or weight lifting. Training increases the ability to eliminate waste products and to sustain contractions. In addition, lactic acid can be used for energy or converted back to pyruvate by the liver, depending on the level of training.

Key Concept Exercise does not increase the number of muscle fibers.The existing fibers just enlarge.

Rehabilitation

Except for the simplest movements, muscles work in groups. An injured or inactive muscle can be retrained or another muscle can be trained to take over its function Therefore, rehabilitation requires working a number of muscles in order to recover function. Rehabilitation is usually performed with the guidance of physical and occupational therapists, but nurses often carry out prescribed exercises. Re-educating muscles is sometimes a long and painful process, and clients need a great deal of encouragement.

MOBILITY

Purposeful, coordinated body movements require integrated functioning between the skeleton, skeletal muscles, and nervous system. Body mechanics is the term used to denote the efficient use of the body as a machine.Increased mobility allows for increased independence. An adult gait pattern (manner of walking) develops between ages 3 and 5. Infants have a wide-based gait and, as children mature, the base narrows. They swing their arms in coordination. Stride and walking speed increase, and movements become smooth. Normal changes of aging may cause the gait of older adults to widen again.

Range of motion (ROM) is the total amount of motion of which a joint is capable. ROM exercises are important for prevention and rehabilitation of musculoskeletal conditions.Lack of mobility can result in changes in most organ systems. Musculoskeletal changes include the following: decreased joint flexibility, decreased muscle tone and strength, and blood clots in the legs (as a result of muscle inactivity, needed to move blood). Tests of muscle function and/or disorders include the blood level of creatine kinase, electromyogram (measurement of electrical activity of muscle tissue), and muscle biopsy. An experimental technique is elastography, which measures the sound produced when a muscle contracts.

TABLE 18-6. Effects of Aging on the Musculoskeletal System

FACTOR

RESULT

NURSING IMPLICATIONS

Bones

Bone mass and strength are lost

Osteoporosis

Assess for fractures

Calcium is lost (greater in postmenopausal women)

Hunched posture (kyphosis: hump-back; lordosis: swayback)

Back pain Brittle bones

Encourage vitamin D and calcium supplements Advise exercise to minimize bone loss Teach safety and prevention of falls Hormone replacement therapy may be prescribed

Vertebral column shortens

Decrease in height (demineralization of bones)

Joints

Degeneration occurs in joints

Arthritis

Osteoarthropathy Joint stiffness

Encourage to increase mobility with active and passive

range-of-motion exercises

Hydrotherapy and external heat often helpful

Muscles

Muscle cells are lost Muscle cells are replaced by fat Elasticity of fibers is lost

Loss of muscle strength Gain of fat tissue (and weight) Loss of flexibility Easy fatigability Resting tremors may occur

Give suggestions on how to carry daily items (e.g., groceries) when it becomes more difficult Encourage to control weight

Suggest walking and swimming (good exercise for older adults); physical activity reduces loss of muscle, tissue, tone, and elasticity; increases flexibility

Advise that exercise promotes psychological stimulation Encourage proper nutrition, particularly adequate protein, vitamins, and minerals

EFFECTS OF AGING ON THE SYSTEM

With aging, individuals gradually lose bone, as well as muscle, strength, and endurance. Muscle cells atrophy (deterioration in cell size and function) and fat cells replace them. Bone tissue does not replace itself as quickly as in younger years. Osteoporosis and fractures may occur because of mineral loss (particularly calcium) from the bones. Women are more likely to be affected by osteoporosis than men because of the reduction of female hormones. Many women take hormone replacements, and both men and women may take vitamin D and calcium supplements to help prevent osteoporosis. Joints may develop osteoarthritis (degenerative joint disease). Muscle aches and back pains may occur, owing to the skeletal changes and to conditions such as kyphosis (hunchback). Table 18-6 summarizes major effects of aging on the musculoskeletal system. It is important to note that disorders can, in many cases, be prevented or arrested by proper preventive care, diet, and exercise.

Prevention of musculoskeletal problems is a nursing consideration. Communicate to clients the importance of appropriate exercise and a diet that includes adequate amounts of proteins and minerals. Calcium is especially important. Adequate vitamin D is also required for the body to metabolize calcium.

Safety is a major consideration. Because of posture and balance adjustments to compensate for skeletal framework changes, older adults are more likely to fall. A common injury in older adults is hip fracture. Because the neck of the head of the femur is smaller than the rest of the femur, demineralization renders this area particularly vulnerable (see Fig. 18-12). After such a fracture, the senior may be more subject to disorders of immobility.

NCLEX Alert The effects of aging are particularly noticeable with muscles and bones. Common NCLEX questions relate to osteoporosis, arthritis, or muscle atrophy among others. The situations may require integration of aging issues, safety communication, and client/family teaching.

Special Considerations: LIFESPAN

Fractures

Fractures in older people heal more slowly because of a decrease in bone metabolism. Calcium and vitamin D supplements may reduce the risk of fractures.

KEY POINTS

•    The skeleton is the living framework of the human body.

•    The four main types of bone are long, short, flat, and irregular.

•    Red bone marrow is found in the ends of long bones, in the bodies of vertebrae, and in flat bones. This bone marrow is responsible for hematopoiesis, the manufacture of red blood cells, white blood cells, and platelets.

•    Joints, bursae, ligaments, and cartilage are responsible for connecting skeletal parts, enabling movement, and protecting the skeleton from injury.

•    The two divisions of the skeleton are the axial skeleton, containing bones of the body’s center, and the appendicular skeleton, containing bones of the extremities.

•    Types of muscle tissue are skeletal or heavily striated (voluntary), smooth or nonstriated (involuntary), and cardiac.

•    Muscle movements are voluntary (controlled by the person) or involuntary.

•    Ossification is the process by which bones become hardened, because of an increase in calcified tissue. Bones change in size and composition during one’s lifetime.

•    Muscles work in groups that have opposing actions. When one paired muscle contracts, the other relaxes.

•    Most body heat is generated from the cellular muscle activity of ATP and oxygen.

•    The musculoskeletal system often loses flexibility and strength as people age.

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