Transient sweat response of the human head during cycling
ABSTRACT This research aims at quantifying transient spatial gradients in sweat production on a human head while cycling.Six test persons were studied. Each test lasted 30 min while a change in work rate was applied after 5 min (from 80 to 150 W for males and from 50 to 125 W for females). Two conditions were analyzed in this research: warm (28.3 ± 0.1 °C, 38 ± 0.6% RH and 0.1 ± 0.1 m/s air velocity) and standard (16.1° ± 0.2 C, 45% ± 0.6 RH and 2.4 ± 0.2 m/s air velocity). Sweat production of the head was measured as a function of time on the right temple, left temple and forehead. This allowed modelling the dynamics of the sweat production response. Constant steady state sweat production, time delay in sweat production, time constant of sweat production and steady state gain of sweat production were quantified and analyzed.Time constants of sweat production were shorter in the warm condition compared to the standard condition. Mean and SEM time constant of sweat production varied from 561 ± 144 s (frontal region) to 1117 ± 230 s (left temple) and 1080 ± 232 s (right temple) in the warm condition. While, at the standard condition, the time constant of sweat production varied from 873 ± 121 s at the frontal region to 1431 ± 195 s at the left temple and 1727 ± 196 s at the right temple. Additionally, also constant steady state sweat production was 0.4–0.7 mg min−1 cm−2 higher in the warm compared to the standard condition (P < 0.05). However, no differences (P > 0.05) were observed for steady state gain and time delay of sweat production between the standard and warm condition.The results of this research can be used to enhance physiological insight of the sweating process and it can also help to develop sweating thermal manikins that behave more realistically to thermal changes. Knowledge of sweat production might also be valuable when designing active controlled headgear since the reaction time of the actuator should take the dynamics of sweat rate into account as a function of work rate and thermal environmental conditions.Relevance to industryUnderstanding of the dynamic behaviour of sweat production in relation to work rate under different environmental conditions allows the design of model based controllers in headgear that actively minimize sweat production. This could help a user's desire to wear a helmet as well as his ability to concentrate.
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ABSTRACT: This study attempts to find the optimal trunk flexion (TF) of a recreational cyclist's subjective discomfort rating while cycling. Two hundred and fifty cyclists were sagittally filmed while cycling on a cycle-way, and their subjective body discomforts were rated. The cyclists also responded to a brief questionnaire. Results show that the TF is positively related to the discomfort on neck/shoulders and is contrary to that on the buttocks. The bike owner cyclists’ (n = 144) trunks were more flexed than the bike rental cyclists’ (n = 106), with a difference of about 11°. This study also found that the cyclists may subjectively perceive the minimum discomforts of both the buttocks and neck/shoulders regions when the trunk was nearly flexed to 38°. This finding serves as a reference for ergonomic consideration in bike design to avoid extreme discomfort while cycling.Journal of the Chinese Institute of Industrial Engineers-JCIIE. 01/2012; 29(8).
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ABSTRACT: The main objective of this study is to establish an approach for measuring the dry and evaporative heat dissipation cricket helmets. A range of cricket helmets has been tested using a sweating manikin within a controlled climatic chamber. The thermal manikin experiments were conducted in two stages, namely the (i) dry test and (ii) wet test. The ambient air temperature for the dry tests was controlled to ∼23 °C, and the mean skin temperatures averaged ∼35 °C. The thermal insulation value measured for the manikin with helmet ensemble ranged from 1.0 to 1.2 clo. The results showed that among the five cricket helmets, the Masuri helmet offered slightly more thermal insulation while the Elite helmet offered the least. However, under the dry laboratory conditions and with minimal air movement (air velocity = 0.08 ± 0.01 ms(-1)), small differences exist between the thermal resistance values for the tested helmets. The wet tests were conducted in an isothermal condition, with an ambient and skin mean temperatures averaged ∼35 °C, the evaporative resistance, Ret, varied between 36 and 60 m(2) Pa W(-1). These large variations in evaporative heat dissipation values are due to the presence of a thick layer of comfort lining in certain helmet designs. This finding suggests that the type and design of padding may influence the rate of evaporative heat dissipation from the head and face; hence the type of material and thickness of the padding is critical for the effectiveness of evaporative heat loss and comfort of the wearer. Issues for further investigations in field trials are discussed.Applied ergonomics 05/2013; · 1.11 Impact Factor
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ABSTRACT: Respirator comfort and fit are two important parameters for respirator design, usage, and standard development. The contact pressure (as measured between a respirator and the wearer) plays an important role in comfort and fit. This work attempts to investigate the contact mechanism and factors that affect the contact pressure. This paper focuses on mechanical factors such as strap tension, strap orientation, strap location, friction, and seal material. A finite element (FE) model-based method was developed to assess the contact pressure. The FE models for both the headform and the respirator have multiple layers. The headform is a medium size headform developed by the National Institute for Occupational Safety and Health (NIOSH) and the respirator is an MSA Affinity Ultra respirator. The results show that the positive Z directional force of strap tension that forces the respirator to move towards the headform is the most important parameter for measuring pressure distribution. Other factors such as strap orientation, friction, strap location, and softness of the seal material were found to affect the contact pressure distribution in this study. Strap orientation and friction coefficient have no significant effect on maximum pressure and maximum shear stress. The dispersive strap location increased the contact pressure on the nose-bridge area of the wearer, while concentrated location had no considerable effect on contact pressure. A softer seal material causes larger deformations and transfers the location of the maximum pressure from the nose-bridge to the tip of the nose.Relevance to industryThis study investigates the effect of important parameters on contact pressure between a respirator and a headform. The sensitivity analysis can provide insights of the interaction between a respirator and a headform. The findings are critical to respirator designers, users, and standard developers to ensure maximal respirator fit and comfort.International Journal of Industrial Ergonomics 01/2011; 41(3):268-279. · 1.21 Impact Factor