OBJECTIVE: The aim of this study was to determine how head and neck postures vary when using two ... more OBJECTIVE: The aim of this study was to determine how head and neck postures vary when using two media tablet (slate) computers in four common user configurations.METHODS: Fifteen experienced media tablet users completed a set of simulated tasks with two media tablets in four typical user configurations. The four configurations were: on the lap and held with the user's hands, on the lap and in a case, on a table and in a case, and on a table and in a case set at a high angle for watching movies. An infra-red LED marker based motion analysis system measured head/neck postures.RESULTS: Head and neck flexion significantly varied across the four configurations and across the two tablets tested. Head and neck flexion angles during tablet use were greater, in general, than angles previously reported for desktop and notebook computing. Postural differences between tablets were driven by case designs, which provided significantly different tilt angles, while postural differences between configurations were driven by gaze and viewing angles.CONCLUSION: Head and neck posture during tablet computing can be improved by placing the tablet higher to avoid low gaze angles (i.e. on a table rather than on the lap) and through the use of a case that provides optimal viewing angles.
Page 1. Force distribution at the hand/handle interface for grip and pull tasks Justin G. Young, ... more Page 1. Force distribution at the hand/handle interface for grip and pull tasks Justin G. Young, Michael E. Sackllah, Thomas J. Armstrong Department of Industrial and Operations Engineering, University of Michigan The purpose ...
【摘要】:Hand/work-object coupling is required to hold and use tools,to transfer work objects,operate... more 【摘要】:Hand/work-object coupling is required to hold and use tools,to transfer work objects,operate controls and support the body.It can be shown biomechanically that coupling entails both active finger flexion and passive friction forces.A laboratory study was conducted to compare ...
ABSTRACT Fall-related fatalities and injuries during climbing tasks represent a significant socio... more ABSTRACT Fall-related fatalities and injuries during climbing tasks represent a significant socioeconomic problem whether they occur in children, in the working age population, or in the elderly. The strength of the mechanical coupling between hand and handhold largely determines if a person can support their bodyweight or will lose grip of the handhold, fall and risk injury. It therefore seems prudent to quantify the maximum amount of external force that the coupling between the hand and handhold is capable of withstanding and to determine how handle design properties influence this.
Biomechanical models were evaluated for effects of handle orientation, handle material, gloves an... more Biomechanical models were evaluated for effects of handle orientation, handle material, gloves and arm posture on maximal pull/push force. Eight healthy subjects performed maximum pull/push exertions on handles with two different orientations and two different surface materials, using bare hand and two types of glove as well as two arm postures. The empirical data supported the proposed biomechanical models: Pull/push forces for the bare hand on a rubber handle decreased 10% when the handle was parallel to the pull/push direction, compared with when perpendicular to it. For parallel handles, pull/push forces further decreased with decreasing hand-handle friction coefficient (simulated by different handle materials and gloves). Pull force exerted by the bare hand was 29% greater when the elbow was extended than when flexed. Pull force was greater than push force (with bare hand and flexed elbow). The biomechanical models suggest that friction between the hand and handle limits pull/push forces for parallel handles. Elbow strength may be responsible for decreased pull force for the flexed elbow posture and decreased force for pull compared with push in the postures examined. STATEMENT OF RELEVANCE: Biomechanical models presented in this paper provide insights for causes of upper extremity strength limitations during pull/push tasks. Findings in this paper can be used directly in the design of workstation and objects to reduce fatigue and risk of musculoskeletal disorders.
OBJECTIVE: The aim of this study was to determine how head and neck postures vary when using two ... more OBJECTIVE: The aim of this study was to determine how head and neck postures vary when using two media tablet (slate) computers in four common user configurations.METHODS: Fifteen experienced media tablet users completed a set of simulated tasks with two media tablets in four typical user configurations. The four configurations were: on the lap and held with the user's hands, on the lap and in a case, on a table and in a case, and on a table and in a case set at a high angle for watching movies. An infra-red LED marker based motion analysis system measured head/neck postures.RESULTS: Head and neck flexion significantly varied across the four configurations and across the two tablets tested. Head and neck flexion angles during tablet use were greater, in general, than angles previously reported for desktop and notebook computing. Postural differences between tablets were driven by case designs, which provided significantly different tilt angles, while postural differences between configurations were driven by gaze and viewing angles.CONCLUSION: Head and neck posture during tablet computing can be improved by placing the tablet higher to avoid low gaze angles (i.e. on a table rather than on the lap) and through the use of a case that provides optimal viewing angles.
Page 1. Force distribution at the hand/handle interface for grip and pull tasks Justin G. Young, ... more Page 1. Force distribution at the hand/handle interface for grip and pull tasks Justin G. Young, Michael E. Sackllah, Thomas J. Armstrong Department of Industrial and Operations Engineering, University of Michigan The purpose ...
【摘要】:Hand/work-object coupling is required to hold and use tools,to transfer work objects,operate... more 【摘要】:Hand/work-object coupling is required to hold and use tools,to transfer work objects,operate controls and support the body.It can be shown biomechanically that coupling entails both active finger flexion and passive friction forces.A laboratory study was conducted to compare ...
ABSTRACT Fall-related fatalities and injuries during climbing tasks represent a significant socio... more ABSTRACT Fall-related fatalities and injuries during climbing tasks represent a significant socioeconomic problem whether they occur in children, in the working age population, or in the elderly. The strength of the mechanical coupling between hand and handhold largely determines if a person can support their bodyweight or will lose grip of the handhold, fall and risk injury. It therefore seems prudent to quantify the maximum amount of external force that the coupling between the hand and handhold is capable of withstanding and to determine how handle design properties influence this.
Biomechanical models were evaluated for effects of handle orientation, handle material, gloves an... more Biomechanical models were evaluated for effects of handle orientation, handle material, gloves and arm posture on maximal pull/push force. Eight healthy subjects performed maximum pull/push exertions on handles with two different orientations and two different surface materials, using bare hand and two types of glove as well as two arm postures. The empirical data supported the proposed biomechanical models: Pull/push forces for the bare hand on a rubber handle decreased 10% when the handle was parallel to the pull/push direction, compared with when perpendicular to it. For parallel handles, pull/push forces further decreased with decreasing hand-handle friction coefficient (simulated by different handle materials and gloves). Pull force exerted by the bare hand was 29% greater when the elbow was extended than when flexed. Pull force was greater than push force (with bare hand and flexed elbow). The biomechanical models suggest that friction between the hand and handle limits pull/push forces for parallel handles. Elbow strength may be responsible for decreased pull force for the flexed elbow posture and decreased force for pull compared with push in the postures examined. STATEMENT OF RELEVANCE: Biomechanical models presented in this paper provide insights for causes of upper extremity strength limitations during pull/push tasks. Findings in this paper can be used directly in the design of workstation and objects to reduce fatigue and risk of musculoskeletal disorders.
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