Abstract:

Significance Protective clothing is used to resist the threat of external flames, ammunition and other threats. However, the bulkiness of the protective clothing will hinder wearer’s mobility and hence performance. The existing evaluation methods for human performance and ability are vulnerable to individual differences in physical fitness and muscle strength, and there is a lack of objective and stable evaluation indicators. Clothing resistance moment refers to the hindrance of clothing to human joint movement, relevant research of which has made remarkable progress. This paper reviews and analyzes the existing evaluation methods and their shortcomings, as well as discusses the influencing factors and applications of clothing resistance moment in research of human performance and ability.

Progress At present, collecting job progress and physiological load index when performing simulated job tasks are the most common evaluation methods for human performance and ability. Job progress and difficulty evaluation are a direct evaluation method for the job itself. Physiological load assessment reflects a person's ability to continue working and potential occupational health risks. The clothing resistance moment is connected with each evaluation metrics. It is mainly affected by the mechanical properties of material, the weight, looseness and detailed structure of clothing. Previous research in functional clothing has led to two types of measurement methods for clothing resistance moment, namely the calculation method based on contact force and measurement method based on the use of equipment. The former uses mechanical sensors or simulation software to measure the contact force between the wearer and clothing, and then convert it to resistance moment, and this method is widely used in tight and stiff clothing. The latter uses test equipment that simulates human activity to measure the clothing resistance moment directly. There are two types of clothing resistance moment test equipment, one is dummy/hand test device and the other is a single joint test device. The dummy device could only test one single size garment, but simulate the contact process between human and clothing. The single joint test device could match various sizes of protective clothing, but the results can only represent the torque required to bend the joint of garment through external forces in an unmanned state. Some studies established the coupling model of human body and clothing to predict the muscle force based on reverse dynamics simulation. Researchers also used clothing resistance moment to predict personnel performance based on statistical analysis.

Conclusion and Prospect At present, due to the limitations of evaluation methods and numerous factors of clothing affecting human performance and ability, the current research is still in the qualitatively exploratory stage. In order to build a stable and reliable evaluation method, further research orientations are proposed. Firstly, clothing resistance moment is a physical clothing characteristic parameter and closely related to all indicators of human performance and ability. Therefore, it can be used as a representative index of clothing mobility for unified judgment of human performance and ability. Secondly, the existing research on the impact of protective clothing are limited to the discussion of a single variable, hence lacking in analysis of the comprehensive effect of multiple factors. As a numerical intermediate variable, the clothing resistance moment can quantitatively guide the ergonomic performance design of protective clothing from the perspective of reducing the resistance moment. Thirdly, it is necessary to put forward more accurate and operable evaluation methods for clothing resistance moment. As for the contact force based calculation method, soft matrix pressure sensors can be considered for measuring distribution of pressure. Regarding the device based measurement method, the compression and friction characteristics of human skin should be simulated to optimize the existing measurement dummies. Finally, due to different experimental conditions and subjects set up in research, it is difficult to quantitatively estimate the influence of protective clothing on job effectiveness. The application of nonlinear models or other empirical formulas and statistical methods can be explored in the prediction of physical exertion or fatigue, so as to avoid the influence of individual differences on the prediction accuracy. Musculoskeletal model with the clothing resistance moment as the external load can also be constructed to analyze the dynamic response of wearers.

Key words: human performance and ability, protective clothing, clothing resistance moment, metabolic cost, muscle strength