The fit between forearm torque force of consumers and required twisting force for opening jars

Abstract

Background and objectives: Opening vacuum-sealed jars can pose a problem for a majority of cosumers because they are unable to exert adequate twisting force. The aims of this study was to evaluate the fit between required force for opening jars and forearm torque strength of comsumers as well aas to propose the optimum force for opening jars based on ergonomic pronciples. Methods: a total of 769 participants (171 from Zanjan city and 598 from Tabriz city) participated in the study. Two measurements were carried out to: 1) determine forearm torque strength pf participants and 2) determine the minimum required twisting force for opening jars. A torque meter (range 0-30 N/m) was used for the purpose of his study. Finally, the fit between required force for opening jars and forearm torque strength of participants were evaluated in the study. Results: The mean required force for opening jars found in the market were 8.6 (SD = 2.4) N/m and 11.9 (SD = 3.2) N/m for small and large size jars, repaectively. The mean forearm torque strength for males and females for small size jars were 4.3 (SD = 1.5) N/m and 3.3 (SD = 0.9) N/m, respectively. The mean forearm torque strength for males and females for large size jars were 4.6 (SD = 1.7) N/m and 3.4 (SD = 0.9) N/m, respectively. The optimum proposed twisting force for opening jars based on the 5th percentile of the studied population (based on gender differences) were 1.4 N/m for small size jars and 1.3 N/m for large size jars, while these values based on age groups were 1.1 N/m and 1.0 N/m for small size and large size jars, respectively. Conlusions: The mean required force for opening both small and large size jars was considerably higher than exerted forearm torque strength of the studied population, which indicates the lack of fit between the required force for opening jars and forearm torque strength of the studied population for all percentiles (i.e. 5th, 50th and 95th).