No description available.

No description available.

No description available.

No description available.

Background: The proportion of elderly in the population is increasing globally. Aerobic capacity (AC) and muscle strength (MS) are important factors for health and quality of life. AC as well as MS decrease with higher age. Increased knowledge about how longitudinal changes in AC and MS covaries could lead to more accurate assessments and exercise recommendations depending on age and fitness level.  Objective: The overall aim was to examine changes in MS and AC from 34 to 63 years of age and if there was an association between the two variables. Specific research questions: (Q1) Is the Two-hand lift (THL) a valid measuring method of knee extensor strength compared to isokinetic knee extension in Biodex®? (Q2) Is there a correlation between VO2max and knee extensor strength on a cross-sectional level at the ages of 63, 52 and 34? (Q3) Is there a correlation between longitudinal changes in knee extensor strength and VO2max from 34 to 63 years of age? (Q4) Is the longitudinal change in physical capacity between 34 and 63 years of age the same in terms of MS and AC?  Methods: Data from a Swedish longitudinal, prospective cohort-study (SPAF) with objective measures of physical capacity from the same sample of women and men since 1974 was used for statistical analysis. A linear regression model was conducted to investigate construct validity of the THL. Knee extension strength (Nm) in Biodex® was set as the dependent variable and kilogram force (kp) in the THL, Jamar® Hand Grip Strength (kg), bodyweight (kg), height (cm) were set as independent variables with sex and exerciser yes/no as factors. A multiple linear regression model was used to explore correlation between MS and AC on a cross-sectional level. VO2max (L/min) estimated according to Ekblom-Bak’s ergometer cycle test was defined as the dependent variable at age 63 and Åstrand’s test at age 34 and 52. MS (kp) in the THL-test, height (cm) and bodyweight (kg) were defined as independent variables. To explore correlation between change in AC and change in MS from 34 to 63 years of age, data from Åstrand’s ergometer cycle test and the THL was used. Differences between repeated measures of VO2max (L/min), bodyweight (kg) and MS (kp) were calculated as quotients that could be analysed with multiple linear regression. A dependent t-test was executed to find out if there was any statistical difference between change in VO2max (L/min) and change in MS (kp) expressed as quotients between 63 and 34 years of age. Results: (Q1)THL showed to be a significant predictor for knee-extensor strength in the Biodex® (R = 0.78, p <.001). (Q2) For the women (n = 67) there was a positive correlation between MS and VO2max (p <.05) at 63 years of age. For the men (n = 74) the correlation was also significant (p <.05) but inversed. At the age of 52 there was a positive correlation (p <.05) for women but not significant for men, and at the age of 34 there was no significant correlation for neither women nor men. (Q3) Change in MS and change in AC did not correlate from 34 to 63 years of age, but from 34 to 52 years of age there was a significant correlation (p <.05). This applied for both women (n = 42) and men (n = 48). (Q4) For the women there was no significant difference between change in MS and change in AC. The average decrease in MS was 7,2% and 15,7% in AC. For the men there was a significant difference between decrease in MS and decrease in AC (p <0.001). The average decrease in MS was 4.5% and 26% in AC. The results were partly dependent on an unexplainable increase in performance on the THL from 52 to 63 years of age that could be due to a systematic measuring error.  Conclusion: The overall results indicate that there is an association between knee extensor muscle strength and VO2max that especially applies to individuals with low physical fitness. Further research with more reliable measuring methods of knee extensor strength is needed to better understand the relationship between muscle strength and aerobic capacity in the ageing population. / Bakgrund: Andelen äldre i befolkningen ökar globalt. Aerob kapacitet (AK) och muskelstyrka (MS) är viktiga faktorer för hälsa och livskvalitet. Både AK och MS minskar med ökad ålder. Ökad kunskap om hur longitudinella förändringar i AK och MS samvarierar skulle kunna leda till mer träffsäkra bedömningar och träningsrekommendationer beroende på ålder och träningsnivå. Syfte: Det övergripande syftet var att undersöka förändring av MS och AK från 34 till 63 års ålder och om det fanns en association mellan de båda variablerna. Specifika frågeställningar: (Q1) Är Tvåhandslyftet (THL) en valid mätmetod för styrka i knäextensor-muskulaturen jämfört med isokinetisk knäextension i Biodex®? (Q2) Finns det en korrelation mellan VO2max och styrka i knäextensor-muskulaturen på tvärsnittlig nivå i åldrarna 63, 52 and 34? (Q3) Finns det en korrelation mellan longitudinella förändringar i knäextensions-muskelstyrka och VO2max från 34 till 63 års ålder? (Q4) Är den longitudinella förändringen av fysisk kapacitet mellan 34 och 63 års ålder densamma i termer av MS och AK? Metod: Data från en svensk longitudinell, prospektiv kohortstudie (SPAF) som samlat objektiva mått på fysisk kapacitet och hälsa från samma urval av kvinnor och män sedan 1974 användes för statistisk analys. Multipel linjär regression användes för att undersöka begreppsvaliditeten avseende THL. Knäextensor-styrka (Nm) i Biodex® definierades som den beroende variabeln och kilogram kraft (kp) i THL, Jamar® handgreppstyrka (kg), kroppsvikt (kg), längd (cm) definierades som oberoende variabler, samt kön och Motionerar ja/nej som faktorer. En multipel linjär regressionsmodell användes för att undersöka korrelation mellan MS och AK vid 63 års ålder. VO2max (l/min) beräknat enligt Ekblom- Baks ergometercykeltest definierades som den beroende variabeln. MS (kp) i Tvåhandslyft- testet, längd (cm) och kroppsvikt (kg) definierades som oberoende variabler. För att undersöka korrelation mellan förändring av AK och förändring av MS från 34 till 63 års ålder användes data från Åstrands ergometercykeltest och THL. Skillnaden mellan upprepade mätningar av VO2max (l/min), kroppsvikt (kg) och muskelstyrka (kp) beräknades till kvoter som kunde analyseras med multipel linjär regression. Ett parat t-test användes för att ta reda på om det var någon statistisk skillnad mellan förändring av VO2max (l/min) och förändring av muskelstyrka (kp) uttryckt som kvoter mellan 63 och 34 års ålder. Resultat: (Q1) THL visade sig vara en statistiskt significant prediktor för knäextensionsstyrka i Biodex® (R = 0.78, p <.001). (Q2) För kvinnorna (n = 67) var det en positiv korrelation mellan muskelstyrka och VO2max (p <.05) vid 63 års ålder. För männen (n = 74) var korrelationen också signifikant (p <.05) men hade en negativ riktning. (Q3) Förändring av muskelstyrka och förändring av VO2max korrelerade inte från 34 till 63 års ålder, men däremot från 34 till 52 års ålder (p <0.05). Detta gällde både kvinnor (n = 42) och män (n = 48). (Q4) För kvinnorna var det ingen signifikant skillnad mellan förändring av muskelstyrka och förändring av VO2max. Den genomsnittliga minskningen i muskelstyrka var 7,2% respektive 15,7% i VO2max. För männen var det en significant skillnad i minskning mellan muskelstyrka och VO2max (p <0.001). Den genomsnittliga minskningen i MS var 4.5% respektive 26% för VO2max. Resultaten berodde delvis på en oförklarlig ökning av prestation i Tvåhandslyft-testet från 52 till 63 års ålder som kan bero på ett systematiskt mätfel. Slutsats: Sammantaget pekar resultaten mot att det finns en association mellan styrka i knäextensor-muskulaturen och VO2max som särskilt gäller individer med låg fysiskkapacitet. Mer forskning med mer reliabla mätmetoder behövs för att bättre förstå sambandet mellan MS och AK i en åldrande population.

High altitude is one of the most extreme environments experienced by terrestrial mammals due to both low ambient temperatures and oxygen availability. Deer mice native to high altitude have a greater thermogenic capacity in hypoxia compared to a lowland population, likely as a consequence of both genetic adaptations and phenotypic plasticity. To understand the adaptive variation in phenotypic plasticity, F1 generation lab-reared mice were acclimated to chronic warm-hypoxia, cold-normoxia, and cold-hypoxia. Acclimation led to equal increases in thermogenic capacity in hypoxia for all stressors in high altitude deer mice. Low altitude mice also increased their thermogenic capacity after acclimation, with a distinct increase after acclimation to cold-hypoxia. The thermogenic capabilities of the high and low altitude mice tested in hypoxia were equal, suggesting that both populations of mice had reached a “metabolic ceiling”. Basal metabolic rate increased after acclimation to cold and cold-hypoxia. Nonshivering thermogenesis was not affected by acclimation or altitude ancestry. Shivering thermogenesis contributed 70 to 80 % of total heat produced during VO2summit across all acclimations, and in both populations. VO2summit in hypoxia was supported by lipids in deer mice even though carbohydrates would provide an oxygen saving advantage. Also, rates of lipid oxidation increased after acclimation to cold, and cold combined with hypoxia in the high altitude population. Together these findings suggest that the increased thermogenic capacity of the high altitude wild mice is based both on differences in phenotypic plasticity, and on differences in genotype from the low altitude mice. Adult phenotypic plasticity is pivotal in the thermogenic capabilities of both populations, and it is likely that developmental plasticity also plays an important role. / Thesis / Master of Science (MSc)

No description available.

No description available.

No description available.

<p>Knowledge on fuel use and muscle metabolism in high altitude mammals is very limited. Yet, as the oxidation of carbohydrates offers an oxygen-saving advantage over the oxidation of fatty acids (15-30% more energy produced per oxygen used), one possible adaptation to maintain performance at high altitude is to elevate the use of carbohydrates as a fuel source for energy metabolism. To test this hypothesis, I performed intraspecific and interspecific comparisons of whole-body fuel use and muscle metabolism in closely related high (4000-4500 m) and low altitude (100-300 m) native mice (genus <em>Phyllotis</em>), which I collected at different locations in Andean and coastal regions of Peru. My results show a higher proportional use of carbohydrates when oxygen becomes limited in high altitude <em>Phyllotis</em> in comparison to their low altitude counterparts. This phenotype does not seem to result from similar phylogenetic history or from a chronic exposure to hypobaric hypoxia during development or adulthood. Accordingly, this thesis provides the first compelling evidence of enhanced carbohydrate utilization as an adaptation to high altitude, a hypothesis proposed nearly 30 years ago. The mechanisms responsible for this shift in fuel use are unknown. There were no strong indications of a greater capacity for carbohydrate oxidation in skeletal and cardiac muscles of high altitude <em>Phyllotis</em> mice. Finally, as this thesis provides the first report of whole-body fuel use in mice, a comparison with other mammalian species (rats, dogs and goats) revealed that the current model of mammalian fuel selection, which is thought to be conserved among mammals, does not apply to small mammals. I thus revisited the current model and proposed a new one general to all mammals. This thesis thus provides significant advancements not only in the field of high altitude physiology but also in the field of mammalian energetics.</p> / Doctor of Philosophy (PhD)