Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Atrophy, Muscular


Related Terms

  • Atrophy of the Muscles
  • Muscle Atrophy
  • Muscle Wasting
  • Wasting

Differential Diagnosis

Specialists

  • Neurologist
  • Occupational Therapist
  • Physiatrist (Physical Medicine and Rehabilitation Specialist)
  • Physical Therapist

Comorbid Conditions

Factors Influencing Duration

The severity of muscular atrophy, the muscle(s) affected, and underlying cause of the atrophy influence the disability period. The individual's ability and willingness to participate in rehabilitation will also be a factor in the length of disability.

Medical Codes

ICD-9-CM:
335.10 - Spinal Muscular Atrophy, Unspecified
335.19 - Spinal Muscular Atrophy, Other; Adult Spinal Muscular Atrophy
356.1 - Peroneal Muscular Atrophy; Charcot-Marie-Tooth Disease; Neuropathic Muscular Atrophy
728.2 - Muscular Wasting and Disuse Atrophy, Not Elsewhere Classified; Myofibrosis, Amyotrophia NOS

Overview

Muscular atrophy is the wasting or loss of muscle tissue resulting either from disease (neurogenic atrophy) or lack of use (disuse atrophy).

In the general population, most muscular atrophy results from disuse. Sedentary jobs and decreased activity as individuals age can result in loss of muscle tone and significant muscular atrophy. Disuse atrophy also can result from immobilization in a cast or sling. Reduced use of a muscle due to joint pain can occur after an injury or following the joint pain and inflammation of severe rheumatoid arthritis. Disuse atrophy may also occur at the same time as a nerve supply interruption, as seen in ankylosing spondylitis. Muscular atrophy caused by lack of use is reversible with appropriate exercise.

Neurogenic atrophy is less common than disuse atrophy and results from diseases affecting the nerves that supply individual muscles (e.g., poliomyelitis, amyotrophic lateral sclerosis [ALS or Lou Gehrig’s disease], Guillain-Barre syndrome) and from muscle diseases (e.g. muscular dystrophy, myotonic dystrophy). In neurogenic atrophy, the nerve supply to the muscle can be interrupted or compromised by compression, injury, or disease within the nerve cells, resulting in temporary or permanent nerve deficit. This can occur with multiple sclerosis, ALS, stroke, or viral infection of the nerve cells. Interruption of nerve function can occur in the brain, spinal cord, or a peripheral nerve. A herniated disc, for example, can result in nerve compression either within the spinal cord or at the point where the nerve exits and becomes a nerve root. A nerve also may be trapped and compressed within certain tight anatomical sites, as in carpal tunnel syndrome or thoracic outlet syndrome. Nerves can be compressed by fluid accumulation and tissue swelling within a confined area of the body (compartment syndrome) following a crush injury, fracture, or a cast that is too tight.

A muscle disease can be intrinsic to muscle tissue, as in muscular dystrophy, polymyositis, or myotonia. It also can occur as a response to systemic illness, such as hypo- or hyperthyroidism, adrenal gland depletion, diabetes mellitus, or an autoimmune disease such as rheumatoid arthritis, polymyalgia, fibromyalgia, or dermatomyositis. Muscular atrophy can be drug-induced from abuse of alcohol or opiates or from prolonged use of steroids. Generalized muscle wasting (cachexia) can occur with advanced cancer, AIDS, or anorexia nervosa. Severe burns, generalized malnutrition, and a prolonged debilitative state also may lead to muscle wasting.

Source: Medical Disability Advisor



Diagnosis

History: A complete history should be obtained, including current and prior illnesses, injuries, medications, and any family history of muscle atrophy. Individuals usually report loss of strength and muscle fatigue. Complaints vary according to the muscles affected (e.g., atrophy of the chest muscles may cause difficulty breathing). Individuals should describe where, when, and how muscle weakness and fatigue began and recount any accompanying symptoms.

Physical exam: The extent of atrophy is determined by clinical observation, noting lack of muscle tone, weakness of the specific muscles, and limb circumference measurements. Sensation and reflexes may or may not be abnormal. The individual may be evaluated for range of motion and gait disturbances.

Tests: A complete blood count (CBC) is done to evaluate health status. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are done to assess the level of inflammation that occurs in muscle diseases such as polymyositis. Blood serum chemistries (creatine kinase, CK or CPK) may be performed to measure muscle enzymes. Electromyography (EMG) may provide helpful diagnostic information. During EMG, needle electrodes are inserted into the muscle to measure the muscle’s action potential, or ability to respond to stimuli. A muscle needle biopsy is sometimes performed under local anesthesia if polymyositis is suspected. Because so many confounding issues surround muscle abnormalities (myopathies), they often are best distinguished using MRI studies that provide more detailed images of tissue.

Source: Medical Disability Advisor



Treatment

The most common treatment for muscular atrophy is regular exercise, often in a physical therapy program. The physical therapist works with the individual's physician to develop a specific program of exercises to help strengthen the affected muscles and restore as much normal function as possible. Electrical stimulation can sometimes facilitate the return of muscle strength via application of a very weak current to the area that painlessly stimulates the muscle. In cases of atrophy caused by some systemic illnesses (e.g., autoimmune disorders), the physician may elect to use intramuscular injections of anabolic steroids. In cases of severe atrophy in which the muscle is in danger of shrinking to such an extent that it contracts a joint and causes further problems, a brace may be applied to the affected area.

Source: Medical Disability Advisor



Prognosis

The outcome of muscular atrophy depends on the underlying cause. Most uncomplicated types of atrophy caused by disuse of a muscle or muscles can be treated with exercise and a full or nearly full recovery can be expected. If the individual has a more complicated underlying medical problem (e.g., ALS, muscular dystrophy), then muscular atrophy can be progressive through the remainder of the individual's life.

Source: Medical Disability Advisor



Rehabilitation

Physical therapy for muscular atrophy depends on the underlying cause, extent, and location of the atrophy. For example, if the individual has sustained an injury that severed the nerves enervating the muscles of the foot, a different protocol is warranted than for someone experiencing a progressive muscular disease (e.g., muscular dystrophy). Muscular atrophy that results from immobility of the affected area from casting or another form of fixation is the easiest and most straightforward to treat.

Overlapping therapeutic strategies are used in all three cases but have common goals. They include increasing or maintaining range of motion for all joints, increasing or maintaining overall muscle integrity and strength, improving muscular efficiency (i.e., decreasing muscular effort when performing activities of daily living), and educating the individual on injury prevention. These goals are met through a progressive exercise routine directed by the physical therapist that also may include the assistance of an occupational therapist or a vocational specialist.

Neuromuscular stimulation of intact motor nerves may be used to maintain range of motion and start the re-education process for the muscle. This type of muscle stimulation can be used while performing movements that pattern appropriate biomechanics for that limb. Low-voltage electromuscular stimulation (EMS) helps stimulate denervated muscles where peripheral nerve damage has occurred. Transcutaneous electrical nerve stimulation (TENS) therapy uses electrodes placed on the skin over the muscle area of interest. By changing the intensity, frequency, and pulse of the current, a sensory effect (decreased pain) or muscular effect (maximal recruitment of muscle fibers) can be noninvasively elicited in the individual.

As the individual gains increased range of motion and stamina, more challenging resistive exercises may be added. The appropriate time for including resistive exercises depends on the type of underlying injury. For example, muscular atrophy related to a fracture can be addressed only after the fracture heals. Regardless of injury type, various methods of water therapy (aquatic rehabilitation) can be used to increase range of motion and facilitate weight bearing without imposing maximal forces of gravity. For those individuals who cannot participate in a pool environment, a whirlpool is effective. Once the individual can bear his or her full weight, the routine may be split between aquatic and standard exercises. Bracing may be required to protect the muscle or joint in some individuals.

Depending on the injury, core strength exercises help improve muscle efficiency and stabilization. An example of a core strength task is to sit or stand on an unstable surface while reaching for an object. If paralysis is involved, recreational therapy using games such as balloon volleyball or billiards can help build functional balance and manual dexterity. Muscle strength is gained through progressive resistive exercises (PREs) with gradual increases in resistance.

An occupational therapist may evaluate the individual's home and work environment, since some individuals may still be fatigued when performing repetitive or labor-intensive tasks such as hammering. Additional support from a vocational rehabilitation specialist may be needed if paralysis or other permanent and debilitating injury is involved. The vocational rehabilitation specialist also is able to help with job placement or job accommodations to meet the individual’s restrictions and limitations.

Individual who experience muscle atrophy from disuse usually recovers within 8 to 12 weeks and should have minimal, if any, problems after return to work. These individuals should continue with a home exercise routine once physical therapy ends. The course of recovery from muscular atrophy that results from other causes is hard to predict and may require up to a year to determine functional outcomes; in some cases, muscular atrophy may be progressive.

Source: Medical Disability Advisor



Complications

Complications of muscular atrophy are highly dependent on the underlying cause of the atrophy. Muscular atrophy in a particular area can result in mechanical strain on other muscles and joints, accelerating wear and fatigue.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

Work restrictions and accommodations are determined on an individual basis, depending on the underlying cause of the muscular atrophy, the muscles affected, and severity of atrophy. An individual with mild disuse atrophy may be able to continue working, but in a limited capacity, until an exercise program builds and tones the affected muscles sufficiently. Individuals with atrophy caused by a progressive disease may need to reduce their physical workload periodically and in some cases permanently.

Company policy on medication usage should be reviewed to determine if prescribed medication use is compatible with job safety and function.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Has individual become inactive? Does individual have a sedentary job?
  • Does individual have any diseases that affect nerves supplying the muscles?
  • Does individual have diseases of the muscle itself?
  • Does individual have a systemic illness?
  • Was individual using or abusing drugs such as opiates, steroids, or alcohol?
  • Did individual wear a cast or experience other immobilization?
  • Does individual complain of loss of strength and muscle fatigue?
  • What muscles are affected? Is there a pattern to the symptoms?
  • On exam, was lack of muscle tone and weakness noted?
  • Were limb circumference measurements done?
  • Were sensation and reflexes diminished, absent, or normal?
  • Were EMG and muscle biopsy done?
  • Were conditions with similar symptoms ruled out?
  • Is there a family history of muscle atrophy in the particular location?

Regarding treatment:

  • Is individual exercising regularly or enrolled in a physical therapy program?
  • Was transcutaneous electrical nerve stimulation (TENS) administered, if appropriate?
  • Was bracing necessary?
  • Were anabolic steroids administered, if appropriate?

Regarding prognosis:

  • Is individual continuing to participate in a home exercise program?
  • Is individual's employer able to accommodate any necessary restrictions?
  • Does individual have any conditions that may affect the ability to recover?
  • Does individual’s muscular atrophy cause mechanical strain affecting other muscles or joints?

Source: Medical Disability Advisor



References

General

"Muscle Atrophy." WrongDiagnosis.com. 19 May 2005 <http://www.wrongdiagnosis.com/sym/muscle_atrophy.htm>.

Source: Medical Disability Advisor






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