The purpose of the present study was to compare total knee arthroplasty (TKA) rehabilitation with and without whole-body vibration (WBV) to 1) understand if WBV is a useful treatment during TKA rehabilitation to increase quadriceps strength and function, and 2) to investigate the effect of WBV on quadriceps voluntary muscle activation. Subject and Methods. Individuals post TKA (WBV n=8, control n=8) received physical therapy with and without WBV for four weeks. Quadriceps strength and muscle activation, function, perceived pain, and knee range of motion were measured. Results. No adverse side effects were reported in either group. There was a significant increase in strength and function for both groups (P<0.01). There was no difference pre to posttest between groups for strength, muscle activation, or pain (Hotelling’s T2=0.42, P=.80) or for function (F=0.54, P=0.66). Discussion and Conclusion. In individuals with TKA, WBV showed equal strength and function improvement to physical therapy directed progressive resistive exercise. Influence of WBV on muscle activation remains unclear, as initial muscle activation was near established normal quadriceps levels and remained so post treatment.

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Bakgrund En handhållen dynamometer (HHD) är ett kliniskt användbart mätverktyg för att mäta muskelstyrka. På Akademiska sjukhuset i Uppsala finns en HHD av märket MicroFET2® (Hoggan Scientific). Det finns ett fåtal studier gjorda som undersöker intrabedömarreliabiliteten vid mätningar av isometrisk muskelstyrka av knäledens muskelgrupper med denna dynamometer. Syfte Syftet med studien var att undersöka den absoluta och relativa reliabiliteten vid mätningar av maximal muskelstyrka i knäledens muskelgrupper med en HHD. Metod Psykometrisk design med test-retest förfarande. Totalt undersöktes 24 friska vuxna vid två mättillfällen med 6–8 dagars mellanrum. Den relativa reliabiliteten presenterades med Intraclass correlation coefficient (ICC 2,1). Den absoluta reliabiliteten presenteras i standard error of measurement (SEM), SEM% samt smallest detectable change (SDC). Resultat Resultaten visade mycket hög relativ reliabilitet för knäledens extensioner (ICC = 0,950,96) och för knäledens flexorer (ICC = 0,94–0,96). SEM varierade mellan 33,58N-34,81N för knäledens extensorer och 14,16N-17,16N för knäledens flexorer. SDC varierade mellan 93,08N–96,49N för knäledens extensorer och 39,25N-47,57N för knäledens flexorer. Konklusion Resultaten indikerar att HHD har mycket hög relativ reliabilitet för bedömning av styrka i knäledens stora muskelgrupper hos ett bekvämlighetsurval med friska vuxna människor.  Den relativa och absoluta reliabiliteten bedömdes överlag vara i enlighet med tidigare studier. För implementering i klinik behöver framtida studier utvärdera absolut och relativ reliabilitet på specifika patientpopulationer. / Background Hand held dynamometry (HHD) is a practical device for testing muscle strength. There is currently a HHD (MicroFET2® - Hoggan Scientific) available at Uppsala University hospital. Few reliability studies excist where the objective is to examine the intra-rater reliability of isometric maximal knee-strength using this device. Objective To examine the absolute and relative reliability of isometric maximal knee-strength using a MicroFET2. Method Psychometric design through test-retest with 6–8 days between measures on 24 healthy adults. The relative reliability expressed as Intra-class correlation coefficient (ICC 2,1) and the absolute reliability as standard error of measurement (SEM), SEM%, and smallest detecatble change (SDC). Results The results of this study showed very good reliability for both knee extensors (ICC = 0,950,96) and knee flexors (ICC = 0,94–0,96). Regarding the absolute reliability SEM ranged from 33,58N-34,81N for knee extensors and 14,16N-17,16N for knee flexors. SDC ranged from 93,08N-96,49N for knee extensors and 39,25N-47,57N for knee flexors. Conclusion The results indicate that HHD has a very good relative reliability for assessing strength in the large muscle groups of the knee joint when examined on a group of healty adults. The relative and absolute reliability was generally in accordance when compared with previous studies. Before being implemented in praxis, future studies need to evaluate absolute and relative reliability on specific patient populations.

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 &lt;.001). (Q2) For the women (n = 67) there was a positive correlation between MS and VO2max (p &lt;.05) at 63 years of age. For the men (n = 74) the correlation was also significant (p &lt;.05) but inversed. At the age of 52 there was a positive correlation (p &lt;.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 &lt;.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 &lt;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 &lt;.001). (Q2) För kvinnorna (n = 67) var det en positiv korrelation mellan muskelstyrka och VO2max (p &lt;.05) vid 63 års ålder. För männen (n = 74) var korrelationen också signifikant (p &lt;.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 &lt;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 &lt;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.

There is a common belief that children compared with adults are at a greater risk for exercise-induced heat illness. However, a limitation of previous studies involves different exercise intensities used in the comparison between children and adults. Dehydration impairs aerobic performance, but its effects on strength are not well understood. Sports drinks are often used as ergogenic aids. There is some evidence to suggest children have a greater reliance on exogenous carbohydrate compared to adults, which could require special considerations when children exercise in the heat. The overall purpose of this thesis was to compare physiological and metabolic responses during exercise in the heat between boys and men. Three studies were conducted to 1) compare the thermoregulatory responses of boys and men exercising in the heat at a fixed absolute metabolic heat production or a fixed metabolic heat production per unit of body mass; 2) compare the effects of 2% hypohydration or, euhydration with and without carbohydrate ingestion during exercise in the heat on subsequent strength in boys and men; and 3) examine the effects of exogenous carbohydrate on endogenous metabolism in boys and men exercising in the heat. Age and body size differences between boys and men did not influence thermoregulatory responses at a fixed metabolic heat production per unit of body mass. No differences in strength were observed among trials. When exercising in the heat, the relative contribution of ingested carbohydrate and endogenous substrate to total energy yield were not different between groups. These findings together have practical implications for boys and men who exercise in the heat. Specifically, moderate exercise in the heat is equally safe for boys and men. The effects of hypohydration and a carbohydrate drink compared to water on muscle strength performance following exercise in the heat are minimal. An important practical application is that carbohydrate intake spared endogenous fuels during exercise in the heat in both groups. / Thesis / Doctor of Philosophy (PhD) / Children may not adapt to temperature extremes as effectively as adults. Thermoregulatory differences may be due to variable exercise intensities prescribed in available child-adult comparisons. Dehydration affects aerobic performance, but its effects on strength are not well understood. Sports drinks are often used to offset dehydration and improve performance; however, the body may have a harder time using sugar drinks when exercising in the heat. The purpose of this thesis was to compare bodily responses of boys and men during exercise in the heat. Our findings have important practical implications for boys and men who exercise and play sports in hot temperatures. Specifically, exercise in the heat is equally safe for boys and men. The effects of hypohydration and a sports drink on muscle strength performance following exercise in the heat are minimal. Finally, although exercise in the heat may affect the use of a sugar drink, boys and men may use this drink to improve aerobic performance, while maintaining hydration levels.

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Objectives: Sarcopenia is defined using a variety of different muscle variables, muscle mass adjustment techniques and cut offs for each variable. The objectives of this thesis were to assess how operational differences in sarcopenia definitions impact the agreement between definitions and the association between sarcopenia and health outcomes such as falls. Methods: A list of sarcopenia definitions was developed which captured the combinations of muscle variables, muscle mass adjustment techniques, and cut offs used in the literature based on a systematic review conducted for this thesis. These definitions were applied to participants taking part in the Canadian Longitudinal Study on Aging, a national study of participants aged 45 to 85 years at baseline. The agreement between the definitions and the association of each definition with falls was assessed. Findings: Both the combination of muscle variables as well as the different muscle mass adjustment techniques generally had limited agreement. Sarcopenia definitions including muscle mass and muscle strength were associated with falls in males, but none of the sarcopenia definitions were associated with falls in females. Area under the curve analyses revealed that even sarcopenia definitions associated with more than two times the odds of falling in males, had a small impact on identifying fallers with values ≤0.56. Conclusions: The results of this thesis show that the existing range of definitions used to define sarcopenia are not equivalent based on the limited agreement and inconsistent association of sarcopenia with falls. The results also show that sarcopenia may have limitations as clinically useful diagnosis for identifying fallers with area under the curve values for all definitions showing that the identification of fallers based on sarcopenic status was at best, modestly better than chance alone. / Thesis / Doctor of Philosophy (PhD) / Definitions for sarcopenia differ in terms of which muscle variables are included, how muscle mass is adjusted, and which cut offs to use for each variables. This thesis assessed the impact of different methods of operationalizing sarcopenia on the proportion of sarcopenic participants, agreement between definitions, and the strength of the association between sarcopenia and falls. The variables used to operationalize sarcopenia as well as different techniques for adjusting muscle mass resulted in poor agreement between definitions. In males, these factors impacted which definitions were significantly associated with falls, and in females, sarcopenia was not associated with falls for any definition. For all definitions, sarcopenia status poorly discriminated between those that would or would not fall. Together, these results show that different sarcopenia definitions are not equivalent and that a standard definition is required. However, this thesis also shows that more work is required to determine the clinical utility of sarcopenia.