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Effects of sweating on distal skin temperature prediction during walking

Introduction

Thermal sensation models require a high quality prediction of local skin temperatures (Tskin,X) from thermoregulation models. However, most thermoregulation models are validated for Tskin,mean under laboratory setting. The objective of this study is to investigate the challenges of simulating distal skin temperatures Tskin,distal during walking.

Methods

For this study, the skin temperature (Tskin) of human subjects (4 males, 2 females) is measured at 15 sites (locations according to [1] plus fingertip) while walking indoors (2.8 met). The subjects wear an everyday outfit consisting of underwear, jeans, T-shirt, long-sleeved shirt, socks and shoes (0.8 clo) [2]. The temperature is recorded every 60 seconds during a one hour experiment. The measured data is then compared to the computed Tskin,X of the mathematical thermoregulation model ThermoSEM [3].

Results

The computed Tskin,mean are within 2 °C of the measured temperatures. The measured Tskin,foot range from 29 °C to 34 °C for all subjects with an increase of 2-3 °C in the course of one hour walking. The computed Tskin,foot largely underestimate the measured values by 4 to 9 °C (Figure 1, light blue squares). For Tskin,hand it differs only 1 to 4 °C. The clothing insulation and metabolic activity are estimates and might differ from reality. By raising the clothing insulation at the foot to a maximal measured value of 2 clo (see [2]) the computed temperatures increase by 3 °C (Figure 1, green crosses). The increase of metabolic rate leads to slightly lower computed Tskin,foot (Figure 1, orange circles). Lower Tskin,foot at increased metabolic rate is due to evaporative heat losses over the entire body because of sweating. If the sweating is neglected in the model, the computed and measured results are in better agreement (Figure 1, red triangles).

Figure 1
figure1

Measured and simulated foot temperature (Tskin, foot) for one male subject while walking indoors (5 minute average). The effects of increased clothing insulation and metabolic rate as well as neglecting sweating are shown.

Discussion

Even though the exclusion of sweating leads to improved results for Tskin,foot, the main issue is the latent heat transport from the foot skin surface to the environment. The current clothing model only includes a total evaporative resistance taken from [4] due to the absence of studies on detailed local evaporative resistances. Therefore new experiments on local (evaporative) clothing resistances are needed.

Conclusions

In order to account for the reduced heat losses when wearing vapour resistant clothing (e.g. shoes), clothing models should differ between sensible and latent heat transport from the skin to the clothing and from the clothing to the environment. Furthermore, experiments are required to quantify the local evaporative resistances more accurately.

References

  1. 1.

    ISO: EN-ISO 9886. Ergonomics - evaluation of thermal strain by physiological measurements. 2004

  2. 2.

    Lee J, Zhang H, Arens E: Typical Clothing Ensemble Insulation Levels for Sixteen Body Parts. In CLIMA Conference. 2013, 9.

  3. 3.

    Kingma BRM, et al: Incorporating neurophysiological concepts in mathematical thermoregulation models. Int J Biometeorol. 2014, 58: 87-99. 10.1007/s00484-012-0628-5.

  4. 4.

    ISO: EN-ISO 9920. Ergonomics of the thermal environment - Estimation of the thermal insulation and water vapour resistance of a clothing ensemble. 2007

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Author information

Correspondence to Stephanie Veselá.

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Keywords

  • Heat Loss
  • Skin Temperature
  • Thermal Sensation
  • Evaporative Heat Loss
  • Reduce Heat Loss