Effects of clothing material on thermoregulatory responses

Effects of clothing material on thermoregulatory responses

Zhang, P

ABSTRACT

The properties of clothing materials critically influence the comfort and performance of the wearer. Clothing is not just a passive cover for the skin: it interacts with and modifies the heat regulating function of the skin, and its effects are modified by the environment. This study investigates the combined effects of the properties of clothing materials and wind on the physiological parameters of human wearers. During exercise, skin temperature, clothing microclimate temperature and relative humidity, clothing surface temperature, body mass loss, and salivary lactic acid concentration are significantly higher for clothing with lower air permeability in a windy environment. Exercise-induced increases in core temperature are also higher for clothing materials with lower air permeability.

Clothing is designed to a much greater extent by fashion and by technological developments than by any scientific analysis of the heat exchange permitted by clothing between the wearer and his environment. But to improve the comfort and performance of the wearer, it is necessary to develop a systematic understanding of the relationship between textile materials and human physiological responses. The water content of clothing fabrics, the motion of water in these fabrics, and the fabric air permeability are all important factors for clothing comfort. In normal stationary conditions, the human body produces little sweat or saturated water vapor. Thus, the wearer may not experience any significant difference in comfort while wearing clothing made of either cotton or polyester, which have different water vapor transmission behaviors [13]. However, during exercising or working in a warm climate, the dry heat flux by conduction, convection, and radiation cannot match the metabolic heat production. Sensible sweating starts to create a latent heat flux by evaporating sweat at the skin surface. Increased sweat evaporation increases the relative humidity of the microclimate with which the clothing is in contact, which can lead to discomfort if adequate vapor transmission is not permitted by the clothing.

One main purpose of clothing is to provide the wearer protection against undesirable environments. The air permeability of a fabric determines its resistance to wind penetration and affects the thermal insulation provided by the clothing. Heat transport accompanies the evaporation and diffusion of water vapor through clothing [5]. Fabric structure, fiber type and yarn details are major factors influencing clothing’s air permeability. Although Hatch et al. found that the skin temperature was not significantly affected by fabric construction [8], Tokura and Natsume found that the rectal temperature of sedentary female subjects was consistently higher in polyester garments than in wool garments in a controlled environment [25]. Clothing insulation and permeability are altered by wind speed as well as by air motion generated by wearer movement. The physical effect of wind can be more accurately measured on a physical apparatus, but in clothing studies, using live subjects to evaluate the effects of wind produces more realistic data. A static manikin measurement can be modified to allow for air motion and for subject-generated air motion [13]. The combined effect of posture and wind speed can reduce the insulation of the surface air layer by up to 80% and the total clothing insulation by up to 53% [9]. Heat and vapor resistance are reduced by increased subject movement and wind [10, 11, 19]. Wind can quickly carry away the warm air surrounding the body, thus evaporating liquid sweat and dissipating the resulting warm vapor [27]. This increases the effectiveness of heat removal by evaporation and results in lower body sweat loss with higher winds during exercise [1].

In this present study, we investigate the combined effects of the properties of clothing materials and wind on human thermoregulatory responses by studying the effects of air permeability during exercise in controlled environments with and without wind.

Conclusions

We have found that physiological responses to heat are influenced by wind and the air permeability of clothing materials. During exercise, skin temperature, clothing microclimate temperature and relative humidity, clothing surface temperature, body mass loss, and salivary lactic acid concentration are significantly lower for clothing with higher air permeability in the environment with wind. An exercise-induced increased core temperature is higher for clothing materials with lower air permeability. These findings are valuable for the development of higher performance sportswear materials because hyperthermia is an important factor limiting exercise performance.

ACKNOWLEDGEMENT

This study was conducted in collaboration with the Research Institute of Human Engineering for Quality Life (HQL), Japan, and was part of the Model Project to Assemble the Human Sensory Database, supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

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P. ZHANG AND R. H. GONG1

Departmant of Textiles, UMHIST, Manchester M60 1QD, United Kingdom

Y. YANAI

Nisshinbo Industries, Miai Research Centre, Miai, Japan

H. TOKURA

Department of Health, Nara Women’s University, Nara, Japan

1To whom all correspondence should be addressed.

Copyright Textile Research Institute Jan 2002

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