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Related Experiment Videos

Expired air temperature during steady-state running

F W Kolkhorst1, T D Toepfer, F A Dolgener

  • 1Human Performance Laboratory, School of Health, Physical Education and Leisure Services, University of Northern Iowa, Cedar Falls 50614-0241, USA. fred.kolkhorst@uni.edu

Medicine and Science in Sports and Exercise
|December 1, 1995
PubMed
Summary

Expired air temperature near the pneumotachometer remains stable during prolonged exercise, whether the device is heated or not. This finding supports using estimated temperatures when direct measurement is unavailable for metabolic systems.

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Area of Science:

  • Exercise Physiology
  • Biomedical Engineering
  • Respiratory Measurement

Background:

  • Metabolic measurement systems often standardize gas volumes using expiratory temperature.
  • Some systems estimate temperature, while others measure it directly.
  • Understanding expiratory temperature stability during exercise is crucial for accurate metabolic data.

Purpose of the Study:

  • To investigate the effect of prolonged exercise on expiratory temperature near the pneumotachometer.
  • To determine if expiratory temperature can be reliably estimated when direct measurement is not feasible.
  • To provide data supporting the use of estimated expiratory temperatures in metabolic analysis.

Main Methods:

  • Seven active females completed two 45-min treadmill runs at a consistent intensity (64.5% +/- 11.8% of VO2max).

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  • The pneumotachometer heater was either set to 37°C or turned off across the two conditions.
  • Expired air temperatures were measured using thermocouples at the nonrebreathing valve (VAL), and 1 cm upstream (UPS) and downstream (DNS) from the pneumotachometer screens.

    • Main Results:

    • No significant temperature differences over time were observed for any condition.
    • No differences in VAL or UPS temperatures were found between the heated and unheated conditions.
    • DNS temperature was significantly higher in the heated condition (30.2 +/- 1.0°C) compared to the unheated condition (27.9 +/- 1.1°C) (P < 0.01).

    Conclusions:

    • Expiratory air temperatures near the pneumotachometer are stable during extended steady-state exercise.
    • The heating status of the pneumotachometer does not significantly affect upstream or valve temperatures.
    • These findings support the estimation of expiratory temperature when direct measurement is not possible in metabolic systems.