Comparison of two telemetric intestinal temperature devices with rectal temperature during exercise.

OBJECTIVE: The discomfort caused by rectal probes and esophageal probes for the estimation of body core temperature has triggered the development of gastrointestinal (GI) capsules that are easily accepted by athletes and workers due to their non-invasive characteristics. We compare two new GI capsule devices with rectal temperature during cycle ergometer exercise and rest. APPROACH: Eight participants followed a protocol of (i) 30 min exercise with a power output of 130 W, (ii) 5 min rest, (iii) 10 min self-paced maximum exercise, and (iv) 15 min rest. Core temperature was measured using two GI-capsule devices (e-Celsius and myTemp) and rectal temperature. MAIN RESULTS: The myTemp system provided only slightly different temperatures to the rectal temperature probe during rest and exercise. However, the factory-calibrated e-Celsius system showed a systematic rectal temperature underestimation of 0.2 °C that is corrected in the 2018 versions. Both GI capsules reacted faster to temperature changes in the body compared to the rectal temperature probe during the rest period following maximum exercise. SIGNIFICANCE: The GI-capsules react faster to temperature changes in the body compared to the rectal temperature probe, in particular during the rest period following exercise.

Heat loss variations of full-face motorcycle helmets.

Heat loss of 27 full-face motorcycle helmets was studied using a thermal manikin headform. The headform was electrically heated and positioned at the exit of a wind tunnel, so that the air stream flowed onto its front side. All helmets were measured in three sessions in which all the vents were opened or closed consecutively in random order. Average heat loss was calculated from a steady state period, under controlled environmental conditions of 22+/-0.05 degrees C, 50+/-1% RH and 50.4+/-1.1 km h(-1) (14.0+/-0.3 ms(-1)) wind speed. The results show large variations in heat loss among the different helmets, ranging from 0 to 4 W for the scalp section of the headform and 8 to 18 W for the face section of the headform. Opening all the vents showed an increase in heat loss of more than 1 W (2 W) for four (two) helmets in the scalp section and six (one) helmets in the face section. These levels of heat transfer have been shown to be the thresholds for human sensitivity in scalp and face sections. Furthermore, helmet construction features which could be identified as important for heat loss of motorcycle helmets were identified.

Heat transfer variations of bicycle helmets.

Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets.