August 2026 Volume 8

SAFETY

MUSCULOSKELETAL ISSUES FACING THE FORGING INDUSTRY By Evelyn King, Ghazal Mashhadiagha, Trinity Blum, Brian Davis, Bud Kinney

Musculoskeletal Loading in the Forging Industry Musculoskeletal loading and associated fatigue profiles specific to forge and metal workers have not been extensively characterized. This is despite the fact that in general, workplace injuries come at a great expense, to both workers and company 1 . An injured worker can experience loss of income, pain and suffering, unaffordable medical bills, and even loss of life. A survey conducted on over five million workers reported back pain from repeated activities at work such as lifting; over one million workers reported that they had stopped working, changed jobs, or made a major change in work activity because of pain/discomfort 2 . A 2004 study developed a risk assessment model for work-related hazards believed to cause carpal tunnel disease and found epidemiologic evidence of a positive association with ergonomic stressors (force, repetitiveness, and hand-arm vibration) 3 . Similarly, Freivalds and colleagues estimated that 37% of back pain worldwide is attributable to occupational hazards 4 .

maximum contractile force of a muscle, working while fatigued is more likely to lead to task failure 5 . Many of these findings are applicable to forging and metalworking because the underlying movement patterns are comparable. Tasks such as hammering, grinding, manipulating tools, and positioning workpieces require repeated shoulder, elbow, and wrist motions over extended periods. Although these actions differ from activities such as placing surgical sutures, installing garment fasteners, or repetitive mouse aiming, the same neuromuscular mechanisms are responsible for controlling repetitive upper-limb motion. Studies of these unrelated occupations have shown that measurable muscular fatigue can develop after as little as 15-20 minutes of continuous work 6 . As this happens, the body compensates by recruiting larger proximal muscle groups to maintain stability and precision, shifting effort from the smaller muscles of the hand toward the biceps, shoulders, and upper back 8 . While this compensation helps sustain task performance, an increase in overall energy expenditure and additional stress on surrounding joints and musculature occurs. The occupations described above generally involve relatively low-force precision tasking, often requiring less than 1 N while still producing measurable muscular fatigue 6 . Forging, however, typically requires substantially greater force production during repetitive hammering, grinding, and material handling 10 . In addition to repetitive loading, forge workers are exposed to high impact forces and hand-arm vibration from striking tools and powered equipment 10 . Hand-arm vibration has been associated with accelerated fatigue development, reduced neuromuscular function, and an increased long-term risk of musculoskeletal disorders such as carpal tunnel syndrome 11 Consequently, the cumulative physical demands placed on forge workers are likely to exceed those observed in many of the occupations used for comparison. Cognitive Fatigue In addition to physical fatigue, forge workers are subject to cognitive fatigue arising from the continuous stream of decisions required throughout the workday. Forging involves repeated assessments of workpiece temperature, hammer strike placement, deformation progression, tool selection, material position, and process timing. Individually, these decisions may appear minor, but together they create substantial cognitive workloads. Research in psychological practices has described this phenomenon as decision fatigue, where the accumulation of numerous small decisions gradually reduces cognitive performance, attention, and decision quality overtime 12 . As cognitive fatigue develops, workers may become less attentive to subtle process changes, slower to recognize hazards, or more likely to rely on habits rather than logical decision-making processes. Physical and cognitive fatigue are also closely related. As muscular fatigue increases, greater mental effort is required to maintain

Figure 1: A study conducted by a team from Cleveland State University (through a grant from FIERF) showed that the top three sites of pain in workers in a forging plant were spine, followed by wrist and shoulder. The repetitive upper-limb movements required in forging can be compared with those of other occupations that have been studied more thoroughly. Workers in industries such as garment manufacturing, construction, surgery, and even esports perform repetitive upper-body tasks that demand varying combinations of motor control, muscular endurance, precision, and strength 5–8 . Research in these fields has demonstrated that prolonged repetitive activity contributes to localized muscle fatigue, reduced motor control, decreased force accuracy, and musculoskeletal injury 6,8,9 . Continuing to work while fatigued can further increase injury risk by requiring greater activation of larger muscle groups to compensate for declining performance 8 . As fatigue decreases the

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