تأثیر قطر ابزار دستی غیر قدرتی در میزان راحتی و حداکثر گشتاور تولید شده دست

مقدمه: ضعف طراحی ابزار دستی و عدم تناسب آن با کاربر یکی از اصلی‌ترین ریسک فاکتورهای اختلالات اسکلتی-عضلانی اندام فوقانی شناخته شده است. آسیب­های ناشی از ابزارهای دستی تقریباً 9% از کل آسیب­های ناشی از کار را شامل می­شود. هدف از انجام این مطالعه بررسی تأثیر قطر ابزار در میزان راحتی و حداکثر گشتاور تولید شده دست و برآورد قطر بهینه ابزار دستی بوده است. مواد و روش ­ها: شرکت‌کنندگان شامل 12 نفر (6 مرد و 6 زن) با میانگین سنی 7/24 و انحراف معیار 84/5 سال می‌باشد. روش پژوهش بدین صورت بوده که هریک از شرکت‌کنندگان با 7 دسته ابزار با قطرهای متنوع به‌وسیله ابزار محقق ساخته سنجش گشتاور دست شروع به اعمال نیرو و چرخاندن دسته ابزار با تمام نیرو می‌کردند. سپس مدت زمان آزمون، حداکثر گشتاور و میزان راحتی دسته ابزار سنجیده و در نهایت آنالیز واریانس و آزمون تی صورت گرفته است. یافته‌ها: میانگین حداکثر گشتاور 88/1 و انحراف معیار 95/0 نیوتن متر، مدت زمان رسیدن به حداکثر گشتاور 96/13 و انحراف معیار 03/9 ثانیه، میانگین راحتی 27/3 و انحراف معیار 48/1 در بازه 1-7 نمره‌ای به دست آمده است. تفاوت معنی­دار بین حداکثر گشتاور تولید شده بین دو گروه مردان و زنان مشاهده شد (001/0 P <). میانگین حداکثر گشتاور 034/3 نیوتن متر و حداکثر سطح راحتی با میانگین 67/4 در قطر چنگش 38 میلی‌متر به دست آمد

Identification of Handbrake Patterns of Young Motorcycle Riders in Thailand Using a Newly Invented Force Measuring Device

The paper aims at identifying handbrake control behavior of young Thai volunteer riders by focusing on small underbone-type of motorcycle using a newly developed force measuring device. The device has been invented to measure the handbrake force using the potentiometer through the fulcrum of hand control lever. Through calibration with the discrete static loads, the relation between the rotational hand control lever and the handbrake force has been determined. This technique is applicable for both hydraulic or cable handbrake systems. It has been employed to measure each rider’s handbrake force against both handbrake levers during brake application. Our sample included thirty volunteers and a professional rider. We conducted the tests based on transportation standard regulation of the United Nations Economic Commission for Europe (UNECE) regulation No. 78, under speed of 40 km/hr. Three types of handbrake patterns have been identified from these tests. Consequently, the force response characteristics from hydraulic and cable systems in motorcycle are notably different. The number of rider’s finger actuation and various patterns applied at the hand brake levers have been revealed to improve the brake skill from young motorcyclists

Investigation of Factors Influencing Ergonomic Characteristics of Water Bottle Handles

Increasingly competitive market environment pushes products and their packaging to meet functional and aesthetic requirements and expectations of consumers. Ergonomic features are one of the most important features for fulfilling consumer expectations and achieving a satisfying user experience. Drinking water in retail is commonly packaged in PET bottles ranging from 0.2 up to 6 litres. The weight of the 6-litre bottle is roughly 6 kilos which can produce strain on the hand while carried from the place of purchase to the place of usage. The goal of this research was to investigate the influence of water bottle handles and to determine how much does handle length, width, and curvature of the grip\u27s edges affect the comfort of product use. This research presents objective experimental measurements and subjective judgment regarding ergonomic characteristics of the 5-6 litre water bottle handles, based on the variations in their shape and dimensions

A Study on Hand Grip Force for Push Activity at Aerospace Industry

Grip strength is the force applied by the hand to push objects and is a specific part of hand strength. It is generally considered that all aspects of the hand must be exercised to produce a healthy and strong grip. The purpose of this study is to analyze the hand grip force that causes discomfort for push activity among the workers in the aerospace industry while workers performing their task. Data were collected by using observation, interview, questionnaires, and Tekscan grip system tools were used to evaluate hand grip pressure force of the workers. Findings show that the individual factors such as age and body size have affected the hand pressure grip force. Besides, the study shows that the hand grip pressure forces when pushing the mold with the right hand are higher than left hand. At the end of this study, the authors concluded that high grip forces will lead to a risk factor for the development of MSDs

Using kinematic reduction for studying grasping postures. An application to power and precision grasp of cylinders

The kinematic analysis of human grasping is challenging because of the high number of degrees of freedom involved. The use of principal component and factorial analyses is proposed in the present study to reduce the hand kinematics dimensionality in the analysis of posture for ergonomic purposes, allowing for a comprehensive study without losing accuracy while also enabling velocity and acceleration analyses to be performed. A laboratory study was designed to analyse the effect of weight and diameter in the grasping posture for cylinders. This study measured the hand posture from six subjects when transporting cylinders of different weights and diameters with precision and power grasps. The hand posture was measured using a Vicon® motion-tracking system, and the principal component analysis was applied to reduce the kinematics dimensionality. Different ANOVAs were performed on the reduced kinematic variables to check the effect of weight and diameter of the cylinders, as well as that of the subject. The results show that the original twenty-three degrees of freedom of the hand were reduced to five, which were identified as digit arching, closeness, palmar arching, finger adduction and thumb opposition. Both cylinder diameter and weight significantly affected the precision grasping posture: diameter affects closeness, palmar arching and opposition, while weight affects digit arching, palmar arching and closeness. The power-grasping posture was mainly affected by the cylinder diameter, through digit arching, closeness and opposition. The grasping posture was largely affected by the subject factor and this effect couldn't be attributed only to hand size. In conclusion, this kinematic reduction allowed identifying the effect of the diameter and weight of the cylinders in a comprehensive way, being diameter more important than weight.We are grateful to the Universitat Jaume I for financial support through project P1·1B2013-33, and the Spanish Ministry of Research and Innovation and the EU (FEDER funds) jointly through projects DPI2010-18177 and DPI2014-52095-P

Med Eng Phys

Inverse dynamics models used to investigate musculoskeletal disorders associated with handle gripping require accurate phalangeal kinetics. Cylindrical handles wrapped with pressure film grids have been used in studies of gripping kinetics. We present a method fusing six degree-of-freedom hand kinematics and a kinematic calibration of a cylinder-wrapped pressure film. Phalanges are modeled as conic frusta and projected onto the pressure grid, automatically segmenting the pressure map into regions of interest (ROIs). To demonstrate the method, segmented pressure maps are presented from two subjects with substantially different hand length and body mass, gripping cylinders 50 and 70 mm in diameter. For each ROI, surface-normal force vectors were summed to create a reaction force vector and center of pressure location. Phalangeal force magnitudes for a data sample were similar to that reported in previous studies. To evaluate our method, a surrogate was designed for each handle such that when modeled as a phalanx it would generate a ROI around the cells under its supports; the classification F-score was above 0.95 for both handles. Both the human subject results and the surrogate evaluation suggest that the approach can be used to automatically segment the pressure map for quantifying phalangeal kinetics of the fingers during cylindrical gripping.CC999999/Intramural CDC HHS/United States2017-02-01T00:00:00Z26709291PMC483042

Measurement of hand/handrim grip forces in two different one arm drive wheelchairs

Purpose. The aim of this study was to explore the total and regional grip forces in the hand when propelling two different manual one arm drive wheelchairs: the Neater Uni-wheelchair (NUW) and a foot steered Action3 wheelchair. Methods. 17 nondisabled users were randomly assigned to each wheelchair to drive around an indoor obstacle course. The Grip, a multiple sensor system taking continuous measurement of handgrip force, was attached to the propelling hand. Total grip force in each region of the hand and total grip force across the whole hand were calculated per user per wheelchair. Results. The Action3 with foot steering only generated significantly greater total grip force in straight running compared to the NUW and also in the fingers and thumb in straight running. Conclusions. The results suggest that the Action3 with foot steering generated greater grip forces which may infer a greater potential for repetitive strain injury in the upper limb. Further work is required to explore whether the difference in grip force is of clinical significance in a disabled population

Grip force vectors for varying handle diameters and hand sizes

Grip force was measured along two orthogonal axes and vector summed. Sixtyone participants recruited from a manufacturing facility (29 men and 32 women) grasped instrumented cylinders (2.54, 3.81, 5.08, 6.35, and 7.62 cm diameter) using a maximal voluntary power grip. Two orthogonal force measurements relative to the third metacarpal were resolved into a magnitude and corresponding angle. On average, magnitude increased 34.8 N as handle diameter increased from 2.54 cm to 3.81 cm, and then monotonically declined 103.8 N as the handle diameter increased to 7.62 cm. The average direction monotonically decreased from 59.20 to 37.7° as handle diameter decreased from the largest to the smallest. When the diameter was smallest, the greatest force component, F,, (168.6 N), was in the direction where the fingertips opposed the palm. Conversely, when the diameter was largest, the smallest component, F,, (77.7 N), was in the same direction. These values are averaged for the left and right hand. The angle for the largest diameter increased with increasing hand size. These relationships should be useful for the design of handles that require gripping in specific directions, such as for hand tools and controls. Actual or potential applications of this research include the design of handles that require gripping in specific directions, such as for hand tools and controls, that reduce effort, and that prevent fatigue and overexertion