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"Cross-adaptation": the effect cold habituation has on the physiological responses to acute hypoxia in humans.

https://arctichealth.org/en/permalink/ahliterature295221
Source
University of Portsmouth. 246 p.
Publication Type
Dissertation
Date
2010
fulfilment of its requirements for the award of the degree of Doctor of Philosophy of the University of Portsmouth. Portsmouth December 2010 ABSTRACT I ABSTRACT Physiological adaptation to environmental stressors is often studied in isolation, but
  1 document  
Author
Lunt, Heather
Source
University of Portsmouth. 246 p.
Date
2010
Language
English
Publication Type
Dissertation
File Size
2398449
Keywords
Acclimatization
Hypoxia
Physiology
Humans
Heart rate
Breathing
Exercise
Water immersion
Catecholamine
Abstract
Physiological adaptation to environmental stressors is often studied in isolation, but these stressors are frequently combined outside of laboratory settings, for example cold and hypoxia at altitude. There is also limited information about the effect that adaptation to one environment has on exposure to another. The five studies in this thesis were conducted in humans to assess the effect cold habituation has on the response to a simulated hypoxic exposure, and also to investigate a possible mechanism through which any change may occur.
A possible site for the =cross-adaptation‘ between cold habituation and hypoxia is the autonomic nervous system. Heart rate variability (HRV) is an non-invasive measurement technique which has been used to quantify autonomic activity. The two main frequency bands of interest when using HRV are referred to as the Low-Frequency (LF) band (the power found between 0.04 and 0.15 Hz) and the High-Frequency (HF) band (the power found between 0.15 and 0.4 Hz). Study One assessed the reliability of heart rate variability as a technique to indicate autonomic activity during both paced (breathing in time to a standard audible signal) and spontaneous breathing conditions, and at different cycling exercise intensities in a thermoneutral environment. It was hypothesised that within each condition HRV indices would be reliable between repeated recordings, which were separated by 96 hours. Eight participants performed each condition on the two occasions. Analysis of the data (coefficients of variation [CV] and intraclass correlation coefficients [ICC]) showed that the paced breathing condition was the most reliable condition, and time domain HRV indices were reliable, whilst not all frequency domain HRV indices were. Normalising and log transforming the raw data did improve reliability and log transformed total and high frequency (Ln HF) power and low:high frequency ratio (Ln LF:HF) met the a priori criteria (CV r=0.8). It was concluded that most log transformed HRV indices were reliable at rest, during paced breathing and during moderate intensity exercise. Thus, the hypothesis was accepted, but caution was advised as several of the indices were close to exceeding the reliability criteria (Ln total power, Ln HF and Ln LF:HF) and a second autonomic measurement technique may be considered to substantiate its use.
The previous study identified that Ln HF power increased when breathing frequency was reduced at rest. Study Two investigated the effect that alterations in breathing patterns had on HRV indices during rest and unloaded seated cycle ergometery (0 Watts) in 16 male participants. It was hypothesised that breathing which was externally paced would increase HF power compared to spontaneous breathing conditions. HF power was elevated during the paced breathing conditions in comparison to spontaneous breathing at rest and during unloaded exercise. Consequently, the hypothesis was accepted. Thus, ventilatory variables should be recorded in following studies as there may be links between ventilation and HRV indices.
The previous studies used participants‘ freely chosen cadence when cycling, this may have influenced the HRV. The third study tested the hypothesis that cycling cadence affected HRV indices. HRV indices from 16 male participants were analysed when cycling at 40, 60, 80 and 100 revs.min-1 on an unloaded (0 Watts) and loaded (100 Watts) seated cycle ergometer. HRV indices declined as cadence was increased. Thus, the hypothesis was accepted. If HRV indices were to be calculated during subsequent experiments, both cadence and power output would have to be standardised.
The first three studies provided information on the conditions which must be present to produce reliable HRV data during moderate intensity exercise. These studies also indicated that an additional means of measuring autonomic activity should be included.
Study Four was designed to establish if one hypoxic exposure would influence a second exposure, if there was no effect the model could be adopted for the final experiment. This study also examined the effect of hypoxia on HRV indices at rest and during exercise. It was hypothesised that exercise and hypoxia would exert separate and additive effects on HRV indices and catecholamine concentrations. Twelve male participants rested and exercised on a loaded cycle ergometer (100 Watts) in normoxic (faction of inspired Oxygen, FIo2 0.2093) and hypoxic conditions (FIo2 0.15) on two occasions, separated by 96 hours. HRV and catecholamine concentrations were similar between the normoxic and hypoxic resting conditions. During exercise in normoxia catecholamine concentrations increased and Ln HF power was reduced, further increases in catecholamine concentrations and a reduction in Ln HF power were found during exercise in hypoxic conditions. The hypothesis was rejected for resting conditions, and accepted for the exercise conditions. It was also found that the first hypoxic exposure did not influence the HRV indices and catecholamine concentrations of the second hypoxic exposure and this model could therefore be used for the final experiment.
The final study (Study Five) tested for the presence of a 'cross-adaptation‘ response in cold habituated humans to hypoxic exposures during rest and moderate intensity exercise. This study was designed on the basis of the information obtained from the previous four experiments and tested the hypothesis that cold habituation by repeated cold-water immersions would reduce the sympathetic activity and cardio-respiratory responses during loaded cycling (100 W) in hypoxic conditions (FIo2 0.12). Thirty-two male participants underwent six, five minute immersions in either cold (12 °C) or thermoneutral (35 °C) water over a three day period. The normoxic and hypoxic exposures were performed before and after the water immersions. It was established that cold habituation attenuated the sympathetic response to loaded exercise during an acute hypoxic exposure and reduced the number and severity of acute mountain sickness (AMS) symptoms. The study provides the first evidence of a cross-adaptation between cold habituation and hypoxic exposure in humans. This was not found in participants who performed thermoneutral water immersions. Therefore, the hypothesis was accepted. In conclusion, in four of four participants whose catecholamine concentrations were analysed and eight from 16 volunteers whose HRV was analysed, showed that cold habituation reduces the sympathetic response to an acute hypoxic stimulus during loaded cycling. However, it is not known if this cross-adaptation provides an adaptive or maladaptive response to prolonged exposure to hypoxia or altitude. ABSTRACT IV Additionally, the permanence of the cross-adaptation also requires further investigation.
Notes
A thesis submitted in partial fulfilment of its requirements for the award of the degree of Doctor of Philosophy of the University of Portsmouth.
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Riddu Riddu, joik or rock-n-roll? A study of Riddu Riddu Festivála and its role as a cultural tool for ethnic revialization [sic].

https://arctichealth.org/en/permalink/ahliterature297029
Source
Faculty of Social Sciences, University of Tromsø, Norway.
Publication Type
Dissertation
Date
April 2008
  1 document  
Author
Leonenko, Anastassia Valerievna
Source
Faculty of Social Sciences, University of Tromsø, Norway.
Date
April 2008
Language
English
Geographic Location
Norway
Publication Type
Dissertation
File Size
1656646
Keywords
International Indigenous Riddu Riddu Festivála
Manndalen
Coastal Saami
Culture
Language
Lifestyle
Revitalisation
Abstract
The International Indigenous Riddu Riddu Festivála has taken place every year since 1991 in Manndalen, a Coastal Saami hamlet, in the municipality of Kåfjord in the county of Troms in the North of Norway. The festival represents by itself an independent event that through indigenous management and developed ethno-relations inside the country, promoting the idea of cultural awareness and sensitivity to all ethnic groups, however different they might be, and support them in terms of preservation of their culture, language, and lifestyle in our global and developed world.
This thesis is intended to show the ambiguity and complexity of the Coastal Saami identity in Manndalen, not only with relation to Norwegians, but also with reference to the situation among locals, between adults and youth, traditions and modernity. In other words, which relations between traditions and modernity does Riddu Riddu demonstrate? Therefore this thesis will try to find out the relation of manndalinger to the cultural invention and show their chosen way of the invasion of traditions and how far they accept distortions as authentic to their heritage during the process of cultural invention and which sign-substitutions can be defined in relation to Coastal Saami culture today. Moreover, the purpose of this thesis is to understand the process by which means invented portions of culture acquire authenticity. In other words, how the social reproduction of culture – the process whereby people learn, embody, and transmit the conventional behaviours of their society (Hanson 1989:898) – is happening in the Coastal Saami community today. Therefore the Riddu Riddu festival will be considered further as one of the examples of Coastal Saami cultural invention with the purpose of revitalization an ethnic identity.
Thus, the Riddu Riddu festival can be seen as a visible tool in Manndalen’s process of ethnic revitalisation. In this case, can the festival be considered as an example of an imagined community (Anderson 1983), created as a cultural arena for the Saami political debates and bringing Saami people, the young and the old generation, together? Further, the festival can be seen as an important tool in the process of Coastal Saami ethnic revitalisation with perspectives on northern indigenous and in general world community nowadays. What is the role of this imagined community for its participants? What challenges do manndalinger have in creating both a local and a global symbolic community?
This master thesis is tended to bring up questions for further discussions and become one of the colourful pieces in the mosaic of understanding the Riddu Riddu festival and its role in the revitalisation of Saami identity.
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