Hand as hammer: A comprehensive review of biomechanical studies related to occupational hand strikes

Abstract

A growing number of workers in modern automotive assembly plants are confronted with occupational tasks involving repeated high-impact hand strikes. Such repetitive physical workloads account for diseases of soft tissues or musculoskeletal disorders in the hand, wrist, or entire upper body. The purpose of this review was to identify and discuss the most pertinent occupational and physiological investigations concerning such hand strikes with particular emphasis on the biomechanical parameters examined. Articles were drawn from four databases to identify publications about occupational hand strikes. First, studies were selected that evaluated hand impact loads measured with the help of force measurement devices.For a deeper understanding of biomechanical factors regarding hand impacts, the scope of the search was extended to include ancillary studies about impacts on wrists or elbows. Overall, 945 abstracts were screened, and five full-text articles were included in the final review. In addition, 34 ancillary articles about impact stress on the hand-arm complex were discussed because of positive relations between high forces, repetition rates or acceleration, and progressing stress in the hand-arm complex identified in studies about critical biomechanical load limits, in the field of fall arrests and sports, i.e. tennis. Furthermore, studies about effective arm movements and body postures during hand strikes as used in martial arts were reviewed. Although certain biomechanical parameters are both known and well documented, studies available at present cannot sufficiently account for specific disorders in the wrist or arm that are triggered by occupational hand strikes.

Analysis of the Contact Area for Three Types of Upper Limb Strikes

“…Its use is in self-defense without any protective equipment and according to the type of strike also in specific combat sports such Kyokushin karate [ 27 ], Mixed Martial Art [ 28 ], Muay Thai [ 29 ]. After the impact of the punch, the force is applied for a short period of time [ 30 ] (less than 50 ms with time to peak 5.08 ± 0.57 ms) [ 31 ] as the product of high mass and acceleration just before the impact [ 32 ]. The speed before the impact is the decisive factor determining the impact force [ 33 , 34 ].…”

“…It is useful to know other variables, such as the striking area of the upper limb, for pressure calculation, potentially leading to alternative head injury assessment compared to the standard peak force criterion [ 35 ]. Previous studies [ 30 , 32 ] show that, in addition to the standard variables, the description of the strike area is not sufficiently addressed even though it may have a major impact on the interpretation of interactive forces and pressures developed in strikes.…”

“…Furthermore, hand morphology relates to performance in various areas of sport [ 40 , 41 ] and determines the handgrip strength [ 42 , 43 , 44 ]. Therefore, the report on the hand contact area has a high potential to inform on the impact characteristics of the strike [ 32 ], where these effects have not yet been investigated.…”

“…Besides strength and size, the skinfold thickness of the hand affects the severity of the impact [ 45 ] where a smaller contact area increases the maximum stress on the target [ 32 ]. Compared to that, the larger contact area results in the lower contact pressure and material strain, thereby higher fracture thresholds have to be assumed in the case of elastic contact characteristics due to the larger contact area [ 37 ].…”

Biomechanical investigation of load differences on the upper extremities in dynamic hand strikes and isometric hand pushes during assembly tasks

“…Unfortunately, the results were not put in the context of biomechanical parameters, such as muscle activity. Other studies found that fist strikes, compared with palm strikes, show increased peak stresses, higher effective mass, and smaller peak acceleration and impulse (Hausmanninger et al, 2019). High acceleration values in palm strikes are described as a risk factor for progressing stress in hand surfaces and soft structures (Cochran et al, 2006).…”