Muscle Strain

Muscle Strain and other Musculoskeletal Disorders – Work-related musculoskeletal disorders are non-traumatic disorders of the soft tissues of the musculoskeletal system. They are caused or aggravated by repetitive forceful motions, awkward postures, use of vibrating tools or equipment, or by manual handling of heavy loads. Frequently, these ergonomic hazards occur in combination, and are aggravated by heat, cold, humidity or other environmental conditions.

Muscle strain due to overuse or repetitive motion – The most common disorder is muscle strain, typically due to repetitive motion or general overuse. In most cases the symptoms do not arise from one acute episode of significant trauma but are the result of continual exposure to repetitive force and micro-trauma that exceeds the ability of the body to recover and adequately repair structural damage. Any activity requiring moderate or greater force, work cycles ≤ 30 seconds or consistently less recovery time than work time in a cycle places the worker at risk. Musculoskeletal pain is a common symptom of muscle strain, and is often the only means of diagnosing the condition. The most recent data available from the National Agricultural Workers Survey show that 11% of agricultural workers have musculoskeletal pain during their first year of work; this increases to 19% by the time they have worked 10+ years.

In addition to general overwork and repetitive motion, certain body locations of muscle strain have been found to be associated with specific types of agricultural activity:

  • Back, neck and shoulder strain – weight bearing, twisting and reaching common in orchard harvest work, and loading and packing of all types of produce;
  • Hand and wrist strain – orchard and vineyard pruning, blueberry raking, dairy farming, nursery and horticulture work;
  • Low back pain and lower extremity pain – stoop work associated with weeding and ground crop harvest work, and blueberry raking.

For more information, see Chronic occupational repetitive strain injury by B. O’Neil and colleagues.

Carpal tunnel syndrome (CTS) – This is the result of compression and entrapment of the median nerve as it passes through the wrist into the hand. When irritated, tendons swell and press against the nearby median nerve. The meat packing industry experiences a high number of CTS cases because workers make up to 10,000 repetitive motions per day in assembly line processes, such as deboning meats, with no variation in motion. Anyone whose job demands a lot of repetitive wrist, hand, and arm motion, which need not always be forceful or strenuous, might experience CTS. For more information, see: Diagnosis, Causation and Treatment of Carpal Tunnel Syndrome: An Evidence-Based Assessment, by Alberta Medical Services Workers’ Compensation Board – Alberta (See page 33 for diagnosis section).

Osteoarthritis – This disorder of the hip and knee has been found to be elevated in dairy work, (milking, tractor driving). Several studies have found associations between dairy work and knee arthritis. One study in NY State found joint pain in five different joints increased with dairy work. These findings indicate that personal risk factors and the intensity and nature of the farm work contribute to joint trouble. For more on osteoarthritis, see: Epidemiology of agriculture-related osteoarthritis, by S. Kirkhorn and colleagues.

Shoulder impingement is sometimes seen as a result of overhead work, particularly repetitive motions and throwing. A NIOSH epidemiological review states that “the evidence for the greatest risk of musculoskeletal disorders due to specific shoulder postures is strongest when there is a combination of exposures to several physical factors such as force and repetitive load /i.e./ holding a tool while working overhead.” Musculoskeletal Disorders and Workplace Factors – A Critical Review of Epidemiologic Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity, and Low Back, NIOSH. For more, see: Evaluation of the patient with shoulder complaints, by Bruce C Anderson, and Ronald J Anderson, Up To Date.

Further farmworker diagnosis and treatment links:

Farmworker prevention and education links:

Back to Common Farmworker Health Conditions and Diagnostic Tools