The Influence of Forearm and Wrist Orientation on Static Grip Strength as a Design Criterion for Hand Tools

Abstract

The amount of force required to use a hand tool and its relationship to the user's capacity to exert this force is a critical design criterion of hand tools, often affecting the immediate safety of the tool user and the propensity of the tool to cause injury to the user with long-term use.wrist is often placed in deviated positions, the available data on grip strength with an undeviated wrist configuration may not be applicable to the design of many hand tools. the decreases in grip strength due to wrist deviations and forearm rotation. The position of maximal static grip strength is the neutral wrist with a supinated forearm. Decrements from the neutral position for wrist flexion, hyperextension, radial flexion and ulnar flexion are 30%, 22%, 18% and 15%, respectively. The pronated forearm allows only 87% of the strength of the supinated forearm, and the differences between the supinated and the midposition forearm are not significant. Because the This study demonstrates INTRODUCTION

Relevance of the EMG/Grip Relationship in Isometric Anisotonic Conditions

“…The variation in grip force according to wrist flexion-extension position and forearm pronation-supination position is comparable to that described in the literature (Ranaivosoa, 1992;Terrel & Purswell, 1976).…”

“…In addition, compared to the reference position, the force rel was slightly lower in supination and considerably lower in pronation. The reduction in force between medium extension and 60° flexion as well as between supination and pronation is primarily due to a variation in the length of the flexor digitorum superficialis muscle (Terrel & Purswell, 1976). In contrast, the reduction in MVC between medium extension and extreme extension would appear to be due to less efficient buttressing of the thenar and hypothenar eminence on the wrist (Terrel & Purswell, 1976).…”

Design of liquid container handles in accordance with user preferences

“…It is well known that musculoskeletal disorders of the forearm are usually caused by excessive deviation of the wrists (Armstrong 1986). Repetitive movements of ulnar deviation, such as pouring liquid out of containers, may cause tenosynovitis and, according to Terrell and Purswell (1976), 'wrist deviation in any direction weakens grip strength, which leads to dropping of tools or limited handling of objects. Injuries may occur or work quality may fall as a result'.…”

Evaluation and Optimization of Handle Design Parameters of a Grass Trimming Machine

“…Therefore, one can conclude that the old shape is more stressful especially if used for a long time. For any wrist position other than neutral, grip strength is reduced [26]. The situation becomes more complicated when vibration is also present.…”