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- Alametsä, Jarmo, et al.
(författare)
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Age‐related circulatory responses to whole body cooling: observations by heart rate variability
- 2015
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Ingår i: Finnish Journal of eHealth and eWelfare. - 1798-0798. ; 7:2-3, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to study potential age ‐ related changes in the circulatory system via heart rate variability (HRV) by gradually lowering ambient temperature (0.2°C/min) from thermoneutral (32 C°) towards cold (18 C°). ECG was recorded from a young (31 years) and from an older subject (78 years), both males. During the tests, brachium blood pressure (BP) was recorded. During the cooling, BP increased in both subjects (young from 95/69 to 132/75 mmHg, old from 125/68 to 176/101 mmHg), the latter exhibiting a prominent rise in diastolic values after cooling. HRV parameters increased in both subjects during the cold exposure being modest in the younger subject as compared to the older one. Also, recovery from the cold in terms of HRV was faster in the younger subject. The present preliminary observations indicate that older age is coupled with altered HRV response to a mild whole‐body skin cooling.
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| 2. |
- Delin, Mattias, et al.
(författare)
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Ascending evacuation - Walking speed in stairs as a function of height
- 2015
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Ingår i: Human Behaviour in fire : 6th International Symposium - 6th International Symposium. - 9780993393303 ; , s. 155-160
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Konferensbidrag (refereegranskat)abstract
- During ascending evacuation in long stairs, there is reason to believe that factors such as fatigue, and change in human behaviour will influence the possibility of satisfactory evacuation and affect the ascending walking speed. Based on these assumption, a 2-year research project was initiated at Lund University. This paper gives a brief description of the project and highlight some initial findings according ascending walking speed and effects of fatigue.
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| 4. |
- Gao, Chuansi, et al.
(författare)
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Validation of standard ASTM F2732 and comparison with ISO 11079 with respect to comfort temperature ratings for cold protective clothing
- 2015
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Ingår i: Applied Ergonomics. - : Elsevier BV. - 1872-9126 .- 0003-6870. ; 46:Online 17 July 2014, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- American standard ASTM F2732 estimates the lowest environmental temperature for thermal comfort for cold weather protective clothing. International standard ISO 11079 serves the same purpose but expresses cold stress in terms of required clothing insulation for a given cold climate. The objective of this study was to validate and compare the temperature ratings using human subject tests at two levels of metabolic rates (2 and 4 MET corresponding to 116.4 and 232.8 W/m(2)). Nine young and healthy male subjects participated in the cold exposure at 3.4 and -30.6 °C. The results showed that both standards predict similar temperature ratings for an intrinsic clothing insulation of 1.89 clo and for 2 MET activity. The predicted temperature rating for 2 MET activity is consistent with test subjects' thermophysiological responses, perceived thermal sensation and thermal comfort. For 4 MET activity, however, the whole body responses were on the cold side, particularly the responses of the extremities. ASTM F2732 is also limited due to its omission and simplification of three climatic variables (air velocity, radiant temperature and relative humidity) and exposure time in the cold which are of practical importance.
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| 6. |
- Halder, Amitava, et al.
(författare)
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Effects of cooling on muscle function and duration of stance phase during gait
- 2015
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Ingår i: Extreme Physiology & Medicine. - : Springer Science and Business Media LLC. - 2046-7648.
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Konferensbidrag (refereegranskat)abstract
- Introduction: Cold exposure alters muscular function. Muscle cooling influences the neuromuscular activation during maximal isometric voluntary contractions (MVC) and the amplitude of surface electromyography (sEMG) [1],[2]. It also slows down the mechanical process during contraction [3]. The purpose of this study was to investigate the effects of local cooling in cold water at 10 °C for 20 min in a climate chamber on lower leg muscle activity and gait pattern. Methods: Sixteen healthy adults (eight females), aged Mean (SD) 27.0(2.9) years; body mass 66.3(9.8) kg; and height 169.5(7.8) cm participated in this experimental study. The median frequency (MF) and mean power frequency (MPF) of sEMG from tibialis anterior (TA) and gastrocnemius medialis (GM) muscles during MVC in ankle planter (PF) and dorsi-flexion (DF) against a hand-held dynamometer as well as contact times on a force plate during gait before and after cooling were measured and analysed. Results: The MF and MPF were significantly lower (P<0.01*) in both TA and GM muscle during MVC and in TA during gait trials after cooling. However, the frequency analysis for GM muscle showed no significant difference (P=0.46 and 0.06, respectively) either in MF or MPF during walking on level surface (table 1). Table 1: The means and SD (Hz) for the MF and MPF of the TA and GM during gait and MVC trials before and after cooling (N=16). sEMG Tibialis Anterior (TA) Gastrocnemius Medialis GM Pre Cooling Post Cooling Pre Cooling Post Cooling Gait MF 83.0±10.2* 69.9±9.6* 81.6±12.6 79.3±11.1 Gait MPF 99.7±11.5* 82.3±11.7* 99.8±13.2 93.2±12.4 MVC MF 87.0±9.7* 50.0±6.1* 111.7±16.7* 90.8±14.8* MVC MPF 100.7±10.6* 59.8±7.7* 129.1±15.3* 101.0±16.1* Fig 1: Duration of stance phase in gait trials. Additionally, the post cooling stance phase over the force plate was significantly (P= 0.013) longer than pre-cooling. Discussion: The significant time difference might be caused by the cold induced MF and MPF decrease in sEMG. Our previous investigation reported that cooling increased the sEMG amplitude and produced fatigue like responses in the leg muscles [2]. Moreover, other studies showed that muscle fatigue resulted in electromechanical delay during cold exposure [1], [4]. Conclusion: Moderate degree and duration of cooling may affect muscle motor unit firing rates, thus shifting the sEMG spectrum to lower frequencies, therefore decreasing the leg muscle force production. The result suggests that muscle cooling can cause cold induced frequency decrease in sEMG similar to fatigue response and lead to reduced muscle performance. References: 1. Cè, E., Rampichini, S., Agnello, L., Limonta, E., Veicsteinas, A., & Esposito, F. (2013). Effects of temperature and fatigue on the electromechanical delay components. Muscle & Nerve, 47(4), 566-576. doi:10.1002/mus.23627. 2. Halder A, Gao C, Miller M. (2014). Effects of cooling on ankle muscle maximum performances, gait ground reaction forces and electromyography. Journal of Sports Medicine.doi:10.1155/2014/520124. 3. Drinkwater, E. (2008). Effects of peripheral cooling on characteristics of local muscle. Medicine and Sport Science, 5374-88. doi:10.1159/000151551. 4. Rampichini, S., Cè, E., Limonta, E., & Esposito, F. (2014). Effects of fatigue on the electromechanical delay components in gastrocnemius medialis muscle. European Journal of Applied Physiology, 114(3), 639-651. doi:10.1007/s00421-013-2790-9.
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| 10. |
- Kuklane, Kalev, et al.
(författare)
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Evaluation of BARRIER® EasyWarm on Healthy Volunteers in Three Different Climates and Verification of the Degree of Correlation Between Tests Performed on Healthy Volunteers and in a standardized bench test
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- INTRODUCTION Anaesthesia induced hypothermia is a common serious but preventable condition associated with increased bleeding and blood transfusion, increased risk for surgical site infections and increased risk for morbid cardiac events. Active warming is effective in preventing hypothermia but there is a need for more easy to use cost-effective products making active warming available to more patients. Establishing how the environment affects skin temperature and total body heat content (TBHC) as well as the correlation between standardized bench tests and healthy volunteer skin temperature is an important aspect in developing new, more effective warming products to prevent or treat hypothermia as this means fewer healthy volunteers are needed as changes to skin temperature could be estimated based on data from bench tests. OBJECTIVES This investigation was undertaken in order to investigate the safety and efficacy of Active warming with BARRIER® EasyWarm when used in three different climate settings and using different test methods; standardized bench test T-1127 measuring temperatures on a wooden board and measuring skin and core temperature on healthy volunteers. An additional objective in this investigation was to determine the degree of correlation between these test methods. OUTCOME A statistically significant increase in TBHC is seen when comparing TBHC over time in all three climates, respectively. With this investigation design we cannot show that there is a difference in TBHC between the different climates though, i.e. the heat generated from the blanket to the subject is not significantly different in the different climates. Based on this investigation the active warming blanket managed to maintain or increase the temperature of the subjects without any adverse thermal effects. Thermal comfort and the mean thermal sensation were maintained between slightly cold and warm throughout the whole exposure length. The active self-warming blanket was well tolerated in healthy male volunteers. None of the six Adverse Events (AE) reported were serious and none of them were related to the investigational device but rather to the immobilisation or the tension of participating in the investigation. All AEs were resolved at end of test. Skin temperature reached maximally 42.2°C, and thus, it never reached the lowest pain threshold of 43°C under any conditions. Increase of core temperature over time in climate 18°C and 24°C was in average 0.1°C to 0.2°C leading to mean final core temperatures of 36.9 (SD 0.2) and 37.1 (SD 0.4) °C for 18°C and 24°C exposures, respectively.
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