Packing Associated Muscle Strain

Introduction – epidemiology

Muscle strain due to overuse or repetitive motion – 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. 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.

The most extensive research on the musculoskeletal effects of orchard packing comes from Washington State (Musculoskeletal Risks in Washington State Apple Packing Companies, by K Snyder, ME Flanagan, JC Map, NJ Simcox, PO Spielholz). In this study, several different types of orchard packing jobs were analyzed. Among all workers, 53% of the workers reported a work related symptom in at least one body site.

Packers reported more than half of the back, hand/wrist, neck, and shoulder problems that met the criteria of being work-related (62%, 64%, 57%, and 68% respectively), although very few workers’ compensation claims had been filed (3%, 4%, 10%, and 0% respectively).

Sorters had a high rate of work-related back, hand/wrist, neck, and shoulder problems (45%, 22%, 11%, and 45% respectively) that resulted in Workers’ Compensation claims rate of 27%, 22%, 0%, and 20% respectively. In addition to Workers’ Compensation costs, nearly 30% of the packers and 36% of the sorters reported than their injuries affected their pace of work, potentially contributing to higher production costs.

Summary of Hazard by Body Site Evaluation: Tool Sorters, Packers, and Segregators

* could not be designated by job type
Evaluation Tool Sorters Packers Segregators
OSHA 200 back, hand/wrist, shoulder, neck*
Observations neck, hand/wrist, forearm, elbow neck, hand/wrist, back, elbow back, wrist, elbow
NIOSH Lifting NA NA back
3-D Static Strength NA NA shoulder, back
Symptoms survey back, shoulder, hand/wrist, neck back, hand/wrist, shoulder, neck shoulder
Risk Perception upper body upper body none noted
Body Discomfort Map- Pre/Post Shift Change shoulder, back, neck, hand/wrist, elbow back, shoulder, hand/wrist, neck, elbow none noted
Body Discomfort Map- Pre Shift hand/wrist for manual baggers, low back for semi-auto tray packers shoulder

Important Contributing Factors

Repetition Manual packing is highly repetitive, with packers handling approximately 13,000 apples per shift. Semi-automatic packing is highly repetitive, and it also has a high force component (baggers hold bags outstretched and tray packers use pinch grips to pull trays). Previous research has found that workers in high-repetition/low-force jobs had a 3 times greater risk of cumulative trauma disorders of the hand and wrist than workers in low repetition/low force jobs; the risk increased to 30 times for high-repetition/high-force jobs.

Static Postures Packing tasks performed by workers in the packing house industry are characterized by repetitive hand and wrist movements and static postures of the neck, arm, and shoulder muscles. Both static posture and repetition can produce injury when there is no break from muscle contraction. Muscles become fatigued when there is no opportunity for blood flow to nourish the muscles and remove waste products.

Manual vs. Semi-automatic work Manual packing is more repetitive than semi-automatic packing; however, it also involves more continual and dynamic body movement. The only two survey tools that could differentiate between manual or semi-automatic packing were job task observations and the across shift discomfort map. No previous studies were found that addressed the effect of increased automation on musculoskeletal risk, self-reported discomfort, or injury. Increased automation may affect a worker’s sense of discomfort because of greater restriction of movement, a sense of loss of control of the work process, and greater monotony reducing motivation.

Age Effect These study findings do not indicate higher symptom reporting or discomfort in older packers. The manual packers were generally older (mean age 47) than semi-automatic packers (mean age 36) and one would expect greater, rather than less, discomfort in an older population since recovering from muscle fatigue takes longer for older workers (deZwart, 1995). This may be due to the role of “survivor bias” (workers who have health problems leave their jobs, and the remaining population includes only those workers whose health has not been adversely affected by their jobs).

If the packing tasks involves overhead work, shoulder impingement is a risk, particularly if it includes 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.” For more, see: Evaluation of the patient with shoulder complaints, by B. Anderson and R. Anderson, UpToDate.

Farmworker diagnosis and treatment links:

Farmworker prevention and education links:

See also Farmworker Patient Education and Prevention Tools

Back to Packing