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- Kuklane, Kalev, et al.
(författare)
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Does reduced heat production during mild whole body cooling override increased heat generation by pre-shivering muscle tension?
- 2011
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Ingår i: Environmental Ergonomics. ; XIV, s. 112-115
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION Preshivering thermogenesis (developing muscle tension) may not be noticed in static situations due to reduced metabolism under mild body cooling. This paper describes the observations of metabolic and heart rate changes under mild body cooling. METHODS Eight men participated in the study. The subjects were dressed in shorts, socks and shoes, and were seated. The air temperature (32 °C) was after 25 minutes gradually reduced to 13°C (0.2 °C/min). Rectal, finger, central skin and air temperatures were recorded. Heart rate was measured continuously. Oxygen consumption was analysed under 5 minutes at 30th and 90th minutes. RESULTS AND DISCUSSION Metabolic rates were commonly decreasing (57((+/-)8 at 30th and 55(+/-)11 W/m2 at 90th minute) during cooling. In one subject (quickest finger cooling and increased final core temperature) the metabolic rate did not reduce. His momentary AVAs reaction indicates a more complex neural input than core cooling. In one subject onset of strong shivering raised metabolism considerably. The mean heart rate of all subjects followed the major trend in metabolic rate (80(+/-)12 at 30th and 72(+/-)12 beats/min at 90th minute). CONCLUSION Increased metabolic rate under mild cooling was not observed, eventually due to the absence of strong enough thermo regulatory responses such as increased muscle tension and superficial shivering. There is a need to repeat the study involving EMG in order to separate thermoregulatory effects from postural effects.
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| 3. |
- Luomala, Matti J., et al.
(författare)
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Adding a cooling vest during cycling improves performance in warm and humid conditions
- 2012
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Ingår i: Journal of Thermal Biology. - : Elsevier BV. - 0306-4565. ; 37:1, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- It is known that warm and humid environment reduces human physical performance. The present study examined whether the use of an ice-vest in such conditions can improve cycling performance. Seven participants cycled with consecutive, non-stop, 10-minute cycles of nine minutes at 60% of their (V) over dot O-2 max punctuated by a one-minute sprint at 80% (V) over dot O-2 max. The cycling protocol was continuously repeated until exhaustion. The protocol was performed with the ice-vest (ICE), worn after 30 min of cycling, and without the ice-vest throughout the protocol (CON). Ventilatory and thermal responses were continuously recorded. Electromyographic (EMG) signals from four muscles of the dominant leg were recorded over one minute, and subjective sensations were evaluated at 10-minute intervals. At exhaustion, the exercise time was recorded. Exercise time improved significantly while wearing the ice-vest from 61 min and 29 s to 74 min and 14 s (+21.5% +/- 7.6: p <0.05). Mean power frequency and amplitude of the EMG revealed decreased neuromuscular fatigue during ICE compared to CON. Ventilatory responses indicated a tendency towards lower ventilation, respiratory quotient was significantly lower and both thermal parameters and subjective sensations indicated lower thermal strain during ICE in comparison to CON. These results suggest that wearing an ice-vest during cycling in warm and humid conditions decreases thermal and physical strain, thereby improving cycling performance. (C) 2011 Elsevier Ltd. All rights reserved.
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| 5. |
- Smolander, Juhani, et al.
(författare)
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Effectiveness of a light-weight ice-vest for body cooling while wearing fire fighter’s protective clothing in the heat
- 2004
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Ingår i: International Journal of Occupational Safety and Ergonomics. - 2376-9130. ; 10:2, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to examine the effects of wearing an ice-vest (ca 1 kg) on physiological and subjective responses in fire fighters. The experiments were carried out on a treadmill in a hot-dry environment. The physical cooling effect of the ice-vest was measured with a thermal manikin. The ice-vest effectively reduced skin temperatures under the vest. On average, heart rate was 10 beats min-1 lower, amount of sweating was reduced by 13%, and subjective sensation of effort and warmth were lower during work with the ice-vest compared to work without it. Thermal manikin tests indicated, that the useful energy available from the vest for body cooling was rather high (58%). In conclusion, the ice-vest reduces physiological and subjective strain responses during heavy work in the heat, and may promote efficient work time by 10%.
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| 8. |
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| 9. |
- Vanggaard, Leif, et al.
(författare)
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Response patterns in finger and central body skin temperatures under mild whole body cooling
- 2011
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Ingår i: Environmental Ergonomics. ; XIV, s. 124-127
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION The actual heat loss may be underestimated especially in studies employing mild whole-body cooling, if AVA-rich distal areas are not taken into account. In the present report, we illustrate the skin temperature response pattern in fingers (rich in AVAs) to transient whole-body cooling as compared to non-acral body sites (without AVAs). METHODS Eight men participated in the study. During the test the subjects were dressed in shorts, socks and shoes and stayed seated with the arms on insulated supports at heart level. The air temperature of 32 °C was after 25 minutes gradually reduced to 13 °C (0.2 °C/min). Core, finger (sulcus lateral to the nailbed) and non-acral skin (8 points) temperatures were measured. RESULTS During cooling the mean skin temperature in all subjects decreased at a similar rate. Higher variation in the end of the cooling could be explained by differences in body fat (R2=0.902). Simultaneously, the finger cooling could start with up to about 1 hour difference in different subjects. DISCUSSION AND CONCLUSION Mean skin temperature did not give any idea on when the subjects left thermal neutrality. It is strongly recommended to measure finger (or toe) temperatures when maintaining the thermal comfort of the subjects in dynamic conditions is important.
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| 10. |
- Vanggaard, Leif, et al.
(författare)
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Thermal responses to whole-body cooling in air with special reference to arteriovenous anastomoses in fingers
- 2012
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 32:6, s. 463-469
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Tidskriftsartikel (refereegranskat)abstract
- The arteriovenous anastomoses (AVAs) in the distal parts of the extremities play a significant role in the heat exchange with the environment. The aim of the study was to examine the thermal responses to whole-body cooling in air, and especially the behaviour of finger skin temperature (Tf, rich in AVAs). Eight young men sat in minimal clothing at 32°C air temperature (Ta), which was then lowered gradually to 13°C in 100 min. In the beginning of cooling, Tf was high and fluctuating, and then suddenly exhibited a rapid fall, while temperatures in other skin sites fell fairly linearly along decreasing Ta to the end of cooling. During the period from start to the rapid fall in Tf, rectal temperature decreased from 37.4°C (SD 0.2) to 37.2°C (0.2), mean skin temperature (Tsk) from 34.6°C (05) to 31.2°C (2.0) and whole-body thermal sensation from ‘slightly warm/warm’ to ‘slightly cool/cold’. The start of the steep fall in Tf varied considerably between individuals in terms of time (2–75 min), Ta (16.7–32.0°C) and Tsk (28.8–34.7°C). On the other hand, the range of Tf at that point was narrower (32.1–35.8°C). The findings stress the importance of taking into account the distal skin temperatures in thermoregulatory studies in addition to the ordinarily used more proximal and central skin sites. Also, it might be advisable to start such experiments with relatively high and fluctuating Tf to guarantee that the thermal state of the subject is well defined.
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