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Introduction: Bone strength is dependent on stimulation by skeletal muscles. To diagnose reduced bone strength and density in children and adolescents is therefore important not only to assess the physical and geometric parameters of bones using densitometric methods, but also to objectively assess parameters of muscle function. "Jumping mechanography" is one of the new techniques used for assessment of muscle force and power. The aim of the thesis was to create the gender-specific pediatric reference data on the main parameters of mechanography, muscle force (Fmax) and muscle power (Pmax). And to increase our knowledge of mechanography by defining relations between indicators mentioned above and basic anthropometrical parameters. Material and Methods: The study population included 796 healthy individuals (432 girls and 364 boys) aged 6-18 years. All probands were examined by a "single two-legged jump" and they were measured for their height and body mass. "Multiple one-legged hopping" was performed in a subgroup of 376 children. The participants were recruited from five primary schools and three high schools. Motoric tests were performed using a portable force platform ("Leonardo Mechanograph® GRFP", Novotec Medical GmbH, Pforzheim). LMS method was used to generate smooth centile curves for parameters...

Este trabalho apresenta como objetivo verificar os efeitos de um programa de 12 semanas de treinamento de força sobre variáveis neuromusculares e composição corporal de crianças e adolescentes. A amostra foi composta por alunos de ambos os sexos, entre 10 a 14 anos de idade, que foram divididos em grupo experimental (GE; n=14) e grupo controle (GC; n=11). Para a classificação maturacional, avaliou-se o pico de velocidade de crescimento e a Escala de Tanner. Foram realizadas as seguintes avaliações: ultrassonografia para analisar a espessura muscular e a eco intensidade; força máxima através do teste de uma repetição máxima (1-RM) de extensores de joelho; pico de torque (PT) isométrico e taxa de produção de torque (TPT), no dinamômetro isocinético; ativação muscular por meio do sinal eletromiográfico (EMG) do Vasto Lateral (VL) e Reto Femoral (RF); potência de membros inferiores, através de saltos com contramovimento (CMJ) em tapete de contato; composição corporal e densidade mineral óssea (DMO) por absorciometria de dupla energia de raios-x (DEXA). Para analisar a normalidade e a homogeneidade dos dados das variáveis dependentes, foram realizados o teste de Shapiro-Wilk e o Teste de Levene, respectivamente. Foi utilizado o teste T independente para comparar as variáveis dependentes no momento basal entre grupos Após, aplicou-se o teste de correlação de Pearson, seguido pelo teste de regressão linear com o método backward, entre as variáveis de caracterização da amostra e as variáveis dependentes, sendo que as variáveis significativas (p<0,05) foram utilizadas como covariantes. Para verificar o efeito do treinamento de força, foi aplicada a análise de variância (ANOVA) de duas vias entre os grupos. O índice de significância adotado foi de 0,05 em todas as comparações. Após 12 semanas de TF, o grupo experimental melhorou a qualidade muscular, espessura muscular do Reto Femoral, 1-RM e TPT 0-100 ms, quando comparado ao grupo controle (p<0,05). A partir disso, pode-se constatar que o treinamento de força induz melhorias no sistema neuromuscular de crianças e adolescentes, melhorando parâmetros de saúde física. / The gold from this study is to verify the effects of a twelve-week strength training program in neuromuscular variables, as well as the body composition from children and teenagers. The sample was comprised by the students of both sexes and divided into: experimental group (EG; n=14) and control group (CG; n=11). For the mature classification, it was evaluated the growth velocity peak (GVP) and the Tunner's stages. The following evaluations were done: ultrasonography to analyze the muscle thickness and echo intensity; maximum strength through the one repetition test (1RM) for the right knee extensors’; isometric peak torque (IPT) and rate of force development (RFD) at the isokinetic dynamometer; muscle activation by eletromiographic signal from the Vastus Laterallis (VL) and Recto Femoris (RF); lower limbs’ power through countermovement jumps (CMJ) at the contact rough; body composition and mineral bone density (MBD) by dual x-ray absormetry (DXA). The normality and homogeneity of the dependent variables were verified from the Shapiro-Wilk and Levene's tests, respectively It was made an independent t test in order to compare the differences between groups for the dependent variables at the basal moment. After, a Pearson correlation test was calculated, followed by a linear regression using the backward method, in order to compare the characterization variables from the sample and the dependent variables, using the ones with significance value (p<0,05) as a covariant. To verify the effect of the strength training, a two way analyzes of variance (ANOVA two way) was made between the groups. The 0,05 level of significance was adopted in all analyzes. After twelve weeks of strength training, the experimental group improved its’ muscle quality, Recto Femoris muscle thickness, 1-RM and RFD 0-100ms, when compared to the control group (p<0,05). From this, it could be stated that strength training induced improvements in the neuromuscular system of children and teenagers, improving physical health parameters.

Aktualumas. Kelio sąnario skausmas yra dažna aktyviai gyvenančių vyrų ir moterų problema. Neretai skausmo priežasties nepavyksta nustatyti, tačiau dėl raumenų silpnumo ir kojų asimetrijos biomechanikos pokyčių skausmai yra dažnesni. Todėl šiame darbe iškėlėme hipotezę, kad po kineziterapijos padidės blauzdos lenkiamųjų ir tiesiamųjų raumenų jėga, sumažės kojų raumenų asimetrija bei išnyks kelio sąnario skausmas. Darbo tikslas — nustatyti blauzdos tiesiamųjų ir lenkiamųjų raumenų jėgos pokyčius taikant KT sportuojantiesiems ir nesportuojantiesiems. Buvo atliktas tyrimas, kuriame dalyvavo 29 tiriamieji: 15 sportuojančių asmenų (3 vyrai ir 12 moterų, amžiaus vidurkis 24,1±3,7 metai) ir 14 nesportuojančių asmenų (4 vyrai ir 10 moterų, amžiaus vidurkis 26,5±6,5 metai). Kineziterapija buvo atliekama Lietuvos Olimpiniame Sporto Centre (LOSC) masažo kabinete. Biodex Medikai System (Biodex Medikai System 3 PRO Sertifikuota ISO 9001 EN 46001) aparatūra buvo registruojama raumenų jėga, kai kampinis greitis buvo 60 l/s, 180 l/s ir 360 l/s. Buvo vertinta kairės ir dešinės blauzdos lenkiamujų ir tiesiamųjų raumenų maksimali jėga, galingumas ir maksimali jėga atitinkanti kūno masę. Gauti duomenys parodė, kad didžiausia raumenų jėga pasiekiama tada, kai sportuojančiųjų ir nesportuojančiųjų kampinis greitis yra mažiausias — 60 l/s. Sportuojančiųjų ir nesportuojančiųjų blauzdos tiesiamieji raumenys yra stipresni už lenkiamuosius esant visiems trims kampiniams greičiams. Kineziterapija labiau... [toliau žr. visą tekstą] / Actuality. The problem of the knee joint pain is frequent among women as well as men who lead an active way of life. Unfortunately, causative factors are difficult to state although muscle weaknesses, asymmetry, biomechanical changes with leg pain are frequent. The hypothesis of this work is that due to physical therapy the power of shin flexion and extension increases while their asymmetry decreases and the knee joint pain disappears. The aim of the work is to define the shin flexion and extension muscle power changes while put up into physical therapy among those who are both sport active and sport passive ones. The research work with 29 participants was done; 15 of them were sport active (3 men and 12 women, the average age of them was 24, 1=3,7years old) the rest 14 sport passive ones (4 men and 10 women, the average age of them was 26, 5= 6, 5 years old). Physical therapy exercises took place at Lithuanian Sport Centre in the massage room. The Biodex Medical System (Biodex Medical System 3PRO Certificated ISO 9001 EN 46001) was registered under the power of 60 l/s, 180 l/s and 360 l/s corner speed. The left and the right shin flexion and extension maximal power of participants were evaluated in comparison with their maximal body mass power. The final results reveal that the strongest power is reached under the low 60 l/s corner speed among people who are sport active as well as sport passive. Physical therapy strengthens more shin flexion muscles among sport active... [to full text]

Este trabalho apresenta como objetivo verificar os efeitos de um programa de 12 semanas de treinamento de força sobre variáveis neuromusculares e composição corporal de crianças e adolescentes. A amostra foi composta por alunos de ambos os sexos, entre 10 a 14 anos de idade, que foram divididos em grupo experimental (GE; n=14) e grupo controle (GC; n=11). Para a classificação maturacional, avaliou-se o pico de velocidade de crescimento e a Escala de Tanner. Foram realizadas as seguintes avaliações: ultrassonografia para analisar a espessura muscular e a eco intensidade; força máxima através do teste de uma repetição máxima (1-RM) de extensores de joelho; pico de torque (PT) isométrico e taxa de produção de torque (TPT), no dinamômetro isocinético; ativação muscular por meio do sinal eletromiográfico (EMG) do Vasto Lateral (VL) e Reto Femoral (RF); potência de membros inferiores, através de saltos com contramovimento (CMJ) em tapete de contato; composição corporal e densidade mineral óssea (DMO) por absorciometria de dupla energia de raios-x (DEXA). Para analisar a normalidade e a homogeneidade dos dados das variáveis dependentes, foram realizados o teste de Shapiro-Wilk e o Teste de Levene, respectivamente. Foi utilizado o teste T independente para comparar as variáveis dependentes no momento basal entre grupos Após, aplicou-se o teste de correlação de Pearson, seguido pelo teste de regressão linear com o método backward, entre as variáveis de caracterização da amostra e as variáveis dependentes, sendo que as variáveis significativas (p<0,05) foram utilizadas como covariantes. Para verificar o efeito do treinamento de força, foi aplicada a análise de variância (ANOVA) de duas vias entre os grupos. O índice de significância adotado foi de 0,05 em todas as comparações. Após 12 semanas de TF, o grupo experimental melhorou a qualidade muscular, espessura muscular do Reto Femoral, 1-RM e TPT 0-100 ms, quando comparado ao grupo controle (p<0,05). A partir disso, pode-se constatar que o treinamento de força induz melhorias no sistema neuromuscular de crianças e adolescentes, melhorando parâmetros de saúde física. / The gold from this study is to verify the effects of a twelve-week strength training program in neuromuscular variables, as well as the body composition from children and teenagers. The sample was comprised by the students of both sexes and divided into: experimental group (EG; n=14) and control group (CG; n=11). For the mature classification, it was evaluated the growth velocity peak (GVP) and the Tunner's stages. The following evaluations were done: ultrasonography to analyze the muscle thickness and echo intensity; maximum strength through the one repetition test (1RM) for the right knee extensors’; isometric peak torque (IPT) and rate of force development (RFD) at the isokinetic dynamometer; muscle activation by eletromiographic signal from the Vastus Laterallis (VL) and Recto Femoris (RF); lower limbs’ power through countermovement jumps (CMJ) at the contact rough; body composition and mineral bone density (MBD) by dual x-ray absormetry (DXA). The normality and homogeneity of the dependent variables were verified from the Shapiro-Wilk and Levene's tests, respectively It was made an independent t test in order to compare the differences between groups for the dependent variables at the basal moment. After, a Pearson correlation test was calculated, followed by a linear regression using the backward method, in order to compare the characterization variables from the sample and the dependent variables, using the ones with significance value (p<0,05) as a covariant. To verify the effect of the strength training, a two way analyzes of variance (ANOVA two way) was made between the groups. The 0,05 level of significance was adopted in all analyzes. After twelve weeks of strength training, the experimental group improved its’ muscle quality, Recto Femoris muscle thickness, 1-RM and RFD 0-100ms, when compared to the control group (p<0,05). From this, it could be stated that strength training induced improvements in the neuromuscular system of children and teenagers, improving physical health parameters.

Este trabalho apresenta como objetivo verificar os efeitos de um programa de 12 semanas de treinamento de força sobre variáveis neuromusculares e composição corporal de crianças e adolescentes. A amostra foi composta por alunos de ambos os sexos, entre 10 a 14 anos de idade, que foram divididos em grupo experimental (GE; n=14) e grupo controle (GC; n=11). Para a classificação maturacional, avaliou-se o pico de velocidade de crescimento e a Escala de Tanner. Foram realizadas as seguintes avaliações: ultrassonografia para analisar a espessura muscular e a eco intensidade; força máxima através do teste de uma repetição máxima (1-RM) de extensores de joelho; pico de torque (PT) isométrico e taxa de produção de torque (TPT), no dinamômetro isocinético; ativação muscular por meio do sinal eletromiográfico (EMG) do Vasto Lateral (VL) e Reto Femoral (RF); potência de membros inferiores, através de saltos com contramovimento (CMJ) em tapete de contato; composição corporal e densidade mineral óssea (DMO) por absorciometria de dupla energia de raios-x (DEXA). Para analisar a normalidade e a homogeneidade dos dados das variáveis dependentes, foram realizados o teste de Shapiro-Wilk e o Teste de Levene, respectivamente. Foi utilizado o teste T independente para comparar as variáveis dependentes no momento basal entre grupos Após, aplicou-se o teste de correlação de Pearson, seguido pelo teste de regressão linear com o método backward, entre as variáveis de caracterização da amostra e as variáveis dependentes, sendo que as variáveis significativas (p<0,05) foram utilizadas como covariantes. Para verificar o efeito do treinamento de força, foi aplicada a análise de variância (ANOVA) de duas vias entre os grupos. O índice de significância adotado foi de 0,05 em todas as comparações. Após 12 semanas de TF, o grupo experimental melhorou a qualidade muscular, espessura muscular do Reto Femoral, 1-RM e TPT 0-100 ms, quando comparado ao grupo controle (p<0,05). A partir disso, pode-se constatar que o treinamento de força induz melhorias no sistema neuromuscular de crianças e adolescentes, melhorando parâmetros de saúde física. / The gold from this study is to verify the effects of a twelve-week strength training program in neuromuscular variables, as well as the body composition from children and teenagers. The sample was comprised by the students of both sexes and divided into: experimental group (EG; n=14) and control group (CG; n=11). For the mature classification, it was evaluated the growth velocity peak (GVP) and the Tunner's stages. The following evaluations were done: ultrasonography to analyze the muscle thickness and echo intensity; maximum strength through the one repetition test (1RM) for the right knee extensors’; isometric peak torque (IPT) and rate of force development (RFD) at the isokinetic dynamometer; muscle activation by eletromiographic signal from the Vastus Laterallis (VL) and Recto Femoris (RF); lower limbs’ power through countermovement jumps (CMJ) at the contact rough; body composition and mineral bone density (MBD) by dual x-ray absormetry (DXA). The normality and homogeneity of the dependent variables were verified from the Shapiro-Wilk and Levene's tests, respectively It was made an independent t test in order to compare the differences between groups for the dependent variables at the basal moment. After, a Pearson correlation test was calculated, followed by a linear regression using the backward method, in order to compare the characterization variables from the sample and the dependent variables, using the ones with significance value (p<0,05) as a covariant. To verify the effect of the strength training, a two way analyzes of variance (ANOVA two way) was made between the groups. The 0,05 level of significance was adopted in all analyzes. After twelve weeks of strength training, the experimental group improved its’ muscle quality, Recto Femoris muscle thickness, 1-RM and RFD 0-100ms, when compared to the control group (p<0,05). From this, it could be stated that strength training induced improvements in the neuromuscular system of children and teenagers, improving physical health parameters.

A betaína é um trimetil derivado do aminoácido glicina. Os seus principais efeitos fisiológicos são atuar como um osmólito e como doador de radicais metil. Especulase que a betaína possa contribuir para a síntese de creatina no músculo esquelético pelo fornecimento de grupos metil, resultante da conversão de betaína em dimetilglicina, para a remetilação de homocisteína em metionina. Os efeitos da suplementação de creatina sobre o desempenho são conhecidos e relacionam-se principalmente ao aumento na ressíntese de fosforilcreatina (PCR). Autores de estudos recentes têm atribuído seus resultados positivos em relação ao aumento de força muscular a um possível efeito da betaína sobre as concentrações de PCR. Essa variável, entretanto, não foi avaliada, de maneira que os mecanismos responsáveis pelo aumento de força advindo da suplementação de betaína ainda são inexplorados em humanos. Diante disso, este estudo teve como objetivo investigar os efeitos da suplementação de betaína, combinada ou não com a suplementação de creatina, sobre as concentrações intramusculares de PCR, e a produção de força e potência muscular em indivíduos não treinados em força. Além disso, as respostas fisiológicas e ergogênicas da suplementação de betaína e creatina foram comparadas e avaliados os possíveis efeitos aditivos desses suplementos. Foi conduzido um estudo duplo-cego, randomizado, controlado por placebo. Trinta e quatro sujeitos foram divididos em quatro grupos: Betaína (BET; 2 g/dia), Creatina (CR; 20 g/dia), Betaína + Creatina (BET + CR; 2 + 20 g/dia) e Placebo (PL). No período basal (PRÉ) e após 10 dias de suplementação (PÓS), os indivíduos submeteram-se a avaliações do consumo alimentar e da composição corporal, a testes de força e potência muscular e à quantificação intramuscular de PCR. Após a intervenção, as concentrações intramusculares de PCR foram maiores nos grupos CR e BET + CR, quando comparados ao grupo PL (p = 0,004 e p = 0,006, respectivamente). Não houve diferenças significativas entre os grupos BET e PL (p = 0,78) e CR e BET + CR (p = 0,99). Os grupos CR e BET + CR apresentaram maior produção de potência muscular no exercício de agachamento, quando comparados ao grupo PL (p = 0,003 e p = 0,041, respectivamente). Resultados similares foram encontrados para o exercício de supino. Os grupos CR e BET + CR também demonstraram aumento significativo de força muscular (teste de 1-RM) do teste PRÉ para o teste PÓS nos exercícios de supino e agachamento (CR: p = 0,027 e p 0,0001; BET + CR: p = 0,03 e p 0,0001 para membros superiores e inferiores, respectivamente). Não houve diferenças significativas para os testes de força e de potência muscular entre os grupos BET e PL e os grupos CR e BET + CR. Também não houve diferença significativa entre os grupos para a composição corporal. O consumo alimentar permaneceu inalterado ao longo do estudo. Os resultados permitem concluir que a suplementação de betaína, combinada ou não com a suplementação de creatina, não aumenta o conteúdo intramuscular de PCR e não afeta o desempenho de força e de potência muscular / Betaine is a trimethyl derivative of the amino acid glycine. The main physiological functions of betaine are to act as an organic osmolyte and as a donor of methyl radicals. It is speculated that betaine may contribute to the synthesis of creatine in skeletal muscle through the donation of a methyl group, resulting from the conversion of betaine to dimethylglycine, to homocysteine to form methionine. The effects of creatine supplementation on performance are well known and are related primarily to an increase in fosforilcreatina resynthesis (PCR). Authors of recent studies have attributed its positive results regarding the increase of muscle strength to a possible effect of betaine on the concentrations of PCR. However, this variable was not assessed, so that the mechanisms responsible for the increase in muscle strength coming from betaine supplementation in humans are still unexplored. In light of this, the aim of this study was to investigate the effect of betaine supplementation combined or not with creatine supplementation on muscle PCR content, muscle strength and power output in non-resistance trained subjects. Additionally, we compared the ergogenic and physiological responses to betaine versus creatine supplementation. Finally, we also tested the possible additive effects of creatine and betaine supplementation. A randomized, double-blind, placebo-controlled study was conducted. Thirty and four subjects were assigned into four groups: Betaine (BET; 2 g/day), Creatine (CR; 20 g/day), Betaine + Creatine (BET + CR; 2 + 20 g/day) or Placebo (PL). At baseline (PRE) and after 10 days of supplementation (POST) body composition, food intake, muscle strength and power and muscle PCR were assessed. The CR and BET + CR groups presented greater increase in muscle PCR content than PL (p = 0.004 and p = 0.006, respectively). PCR content was comparable between BET versus PL (p = 0.78) and CR versus BET + CR (p = 0.99). CR and BET + CR presented greater muscle power output than PL in the squat exercise following supplementation (p = 0.003 and p = 0.041, respectively). Similarly, bench press average power was significantly greater for the CR-supplemented groups. CR and BET + CR groups also showed significant pre- to post-test increase in 1-RM squat and bench press (CR: p = 0.027 and p 0.0001; BET + CR: p = 0.03 and p 0.0001 for upper- and lower-body assessments, respectively). No significant differences for 1-RM strength and power were observed between BET versus PL and CR versus BET + CR. Body composition did not differ between the groups. Dietary intake was unchanged throughout the study. Thus, we concluded that betaine supplementation does not augment muscle PCR content and betaine supplementation combined or not with creatine supplementation does not affect strength and power performance in non-resistance trained subjects

A betaína é um trimetil derivado do aminoácido glicina. Os seus principais efeitos fisiológicos são atuar como um osmólito e como doador de radicais metil. Especulase que a betaína possa contribuir para a síntese de creatina no músculo esquelético pelo fornecimento de grupos metil, resultante da conversão de betaína em dimetilglicina, para a remetilação de homocisteína em metionina. Os efeitos da suplementação de creatina sobre o desempenho são conhecidos e relacionam-se principalmente ao aumento na ressíntese de fosforilcreatina (PCR). Autores de estudos recentes têm atribuído seus resultados positivos em relação ao aumento de força muscular a um possível efeito da betaína sobre as concentrações de PCR. Essa variável, entretanto, não foi avaliada, de maneira que os mecanismos responsáveis pelo aumento de força advindo da suplementação de betaína ainda são inexplorados em humanos. Diante disso, este estudo teve como objetivo investigar os efeitos da suplementação de betaína, combinada ou não com a suplementação de creatina, sobre as concentrações intramusculares de PCR, e a produção de força e potência muscular em indivíduos não treinados em força. Além disso, as respostas fisiológicas e ergogênicas da suplementação de betaína e creatina foram comparadas e avaliados os possíveis efeitos aditivos desses suplementos. Foi conduzido um estudo duplo-cego, randomizado, controlado por placebo. Trinta e quatro sujeitos foram divididos em quatro grupos: Betaína (BET; 2 g/dia), Creatina (CR; 20 g/dia), Betaína + Creatina (BET + CR; 2 + 20 g/dia) e Placebo (PL). No período basal (PRÉ) e após 10 dias de suplementação (PÓS), os indivíduos submeteram-se a avaliações do consumo alimentar e da composição corporal, a testes de força e potência muscular e à quantificação intramuscular de PCR. Após a intervenção, as concentrações intramusculares de PCR foram maiores nos grupos CR e BET + CR, quando comparados ao grupo PL (p = 0,004 e p = 0,006, respectivamente). Não houve diferenças significativas entre os grupos BET e PL (p = 0,78) e CR e BET + CR (p = 0,99). Os grupos CR e BET + CR apresentaram maior produção de potência muscular no exercício de agachamento, quando comparados ao grupo PL (p = 0,003 e p = 0,041, respectivamente). Resultados similares foram encontrados para o exercício de supino. Os grupos CR e BET + CR também demonstraram aumento significativo de força muscular (teste de 1-RM) do teste PRÉ para o teste PÓS nos exercícios de supino e agachamento (CR: p = 0,027 e p 0,0001; BET + CR: p = 0,03 e p 0,0001 para membros superiores e inferiores, respectivamente). Não houve diferenças significativas para os testes de força e de potência muscular entre os grupos BET e PL e os grupos CR e BET + CR. Também não houve diferença significativa entre os grupos para a composição corporal. O consumo alimentar permaneceu inalterado ao longo do estudo. Os resultados permitem concluir que a suplementação de betaína, combinada ou não com a suplementação de creatina, não aumenta o conteúdo intramuscular de PCR e não afeta o desempenho de força e de potência muscular / Betaine is a trimethyl derivative of the amino acid glycine. The main physiological functions of betaine are to act as an organic osmolyte and as a donor of methyl radicals. It is speculated that betaine may contribute to the synthesis of creatine in skeletal muscle through the donation of a methyl group, resulting from the conversion of betaine to dimethylglycine, to homocysteine to form methionine. The effects of creatine supplementation on performance are well known and are related primarily to an increase in fosforilcreatina resynthesis (PCR). Authors of recent studies have attributed its positive results regarding the increase of muscle strength to a possible effect of betaine on the concentrations of PCR. However, this variable was not assessed, so that the mechanisms responsible for the increase in muscle strength coming from betaine supplementation in humans are still unexplored. In light of this, the aim of this study was to investigate the effect of betaine supplementation combined or not with creatine supplementation on muscle PCR content, muscle strength and power output in non-resistance trained subjects. Additionally, we compared the ergogenic and physiological responses to betaine versus creatine supplementation. Finally, we also tested the possible additive effects of creatine and betaine supplementation. A randomized, double-blind, placebo-controlled study was conducted. Thirty and four subjects were assigned into four groups: Betaine (BET; 2 g/day), Creatine (CR; 20 g/day), Betaine + Creatine (BET + CR; 2 + 20 g/day) or Placebo (PL). At baseline (PRE) and after 10 days of supplementation (POST) body composition, food intake, muscle strength and power and muscle PCR were assessed. The CR and BET + CR groups presented greater increase in muscle PCR content than PL (p = 0.004 and p = 0.006, respectively). PCR content was comparable between BET versus PL (p = 0.78) and CR versus BET + CR (p = 0.99). CR and BET + CR presented greater muscle power output than PL in the squat exercise following supplementation (p = 0.003 and p = 0.041, respectively). Similarly, bench press average power was significantly greater for the CR-supplemented groups. CR and BET + CR groups also showed significant pre- to post-test increase in 1-RM squat and bench press (CR: p = 0.027 and p 0.0001; BET + CR: p = 0.03 and p 0.0001 for upper- and lower-body assessments, respectively). No significant differences for 1-RM strength and power were observed between BET versus PL and CR versus BET + CR. Body composition did not differ between the groups. Dietary intake was unchanged throughout the study. Thus, we concluded that betaine supplementation does not augment muscle PCR content and betaine supplementation combined or not with creatine supplementation does not affect strength and power performance in non-resistance trained subjects

Patients admitted to intensive care unit (ICU) are known to develop significant impairments in physical function. Patients with critical illness suffer up to 30% reductions in muscle size within the first ten days of admission to the ICU. Muscle strength testing, Medical Research Council-sum score, is current gold-standard to diagnosis ICU-acquired weakness and predicts risk of mortality and long-term physical function. Muscle power different from muscle strength in that it accounts for velocity of movement, is potentially a better independent predictor of function that has not been studied in this population. In addition, we hypothesize that muscle size and quality measured through ultrasound imaging has better applicability and prediction that strength testing. Therefore, we prospectively collected data surrounding these muscle parameters in patients admitted to the medicine ICU at University of Kentucky. Primary outcomes included physical function, muscle power with a novel assessment tool for the critically ill population, muscle strength, and muscle size and quality assess through ultrasound imaging. 36 patients admitted to ICU and 18 aged-matched controlled were enrolled. Patients had significantly lower scores on muscle power assessment at ICU discharge (33.6 ±19.0 W; t= 4.01, p < 0.001) and at hospital discharge (40.9 ±16.5 W; t= 4.81, p < 0.001) in comparison to controls (59.3± 14.7 W). Patients with better scores on muscle power assessment had significantly better scores on physical function measures (Six-minute walk test; rs = 0.548, p = 0.0001). Muscle size (cross-sectional area of rectus femoris muscle) and muscle power were strongly correlated (rs = 0.66, p < 0.0001). These data suggest that patients with critical illness have significantly reduced muscle power which directly related to deficits in physical function.

Background: Knee osteoarthritis is a degenerative disease characterized by damaged joint tissues (e.g., cartilage) that leads to joint pain, and reduced mobility and quality of life. Various factors are involved in disease progression, including biomechanical, patient-reported outcome and mobility measures. This thesis provides important longitudinal data on the role of these factors in disease progression, and the trajectory of biomechanical factors in persons with knee osteoarthritis. Objectives: (1) Determine the extent to which changes over 2.5 years in knee cartilage thickness and volume in persons with knee osteoarthritis were predicted by the knee adduction and flexion moment peaks, and knee adduction moment impulse and loading frequency. (2) Determine the extent to which changes over 2 years in walking and stair-climbing mobility in women with knee osteoarthritis were predicted by quadriceps strength and power, pain and self-efficacy. (3) Estimate the relative and absolute test-retest reliabilities of biomechanical risk factors for knee osteoarthritis progression. Methods: Data were collected at 3-month intervals during a longitudinal (3-year), observational study of persons with clinical knee osteoarthritis (n=64). Magnetic resonance imaging of the study knee was acquired at the first and last assessments, and used to determine cartilage thickness and volume. Accelerometry and dynamometry data were acquired every 3 months, and used to determine knee loading frequency and knee muscle strength and power, respectively. Walking and stair-climbing mobility, as well as pain and self-efficacy data, were also collected every 3 months. Gait analyses were performed every 6 months, and used to calculate lower-extremity kinematics and kinetics. Results: (1) The knee adduction moment peak and impulse each interacted with body mass index to predict loss of medial tibial cartilage volume over 2.5 years. These interactions suggested that larger joint loads in those with a higher body mass index were associated with greater loss of cartilage volume. (2) In women, lower baseline self-efficacy predicted decreased walking and stair ascent performances over 2 years. Higher baseline pain intensity/frequency also predicted decreased walking performance. Quadriceps strength and power each interacted with self-efficacy to predict worsening stair ascent times. These interactions suggested that the impact of lesser quadriceps strength and power on worsening stair ascent performance was more important among women with lower self-efficacy. (3) Relative reliabilities were high for the knee adduction moment peak and impulse, quadriceps strength and power, and body mass index (i.e., intraclass correlation coefficients >0.80). Absolute reliabilities were high for quadriceps strength and body mass index (standard errors of measurement <15% of the mean). Data supported the use of interventions effective in reducing the knee adduction moment and body mass index, and increasing quadriceps strength, in persons with knee osteoarthritis. Conclusion: Findings from this thesis suggest that biomechanical factors play a modest independent role in the progression of knee osteoarthritis. However, in the presence of other circumstances (e.g., obesity, low self-efficacy, high pain intensity/frequency), biomechanical factors can vastly worsen the disease. Strategies aiming to curb structural progression and improve clinical outcomes in knee osteoarthritis should target biomechanical and clinical outcomes simultaneously. / Thesis / Doctor of Philosophy (PhD) / Knee osteoarthritis is a multifactorial disease whose progression involves worsening joint structure, symptoms, and mobility. Various factors are linked to the progression of this disease, including biomechanical, patient-reported outcome and mobility measures. This thesis provides important information on how these factors, separately and collectively, are involved in worsening disease over time, as well as benchmarks that are useful to clinicians and researchers in interpreting results from interventional or longitudinal research. First, we examined how different elements of knee loading were associated with changes in knee cartilage quantity over time in persons with knee osteoarthritis. Second, we examined how different elements of knee muscle capacity and patient-reported outcomes were related to changes in mobility over time in persons with knee osteoarthritis. Third, we examined the stability over time of various biomechanical risk factors for the progression of knee osteoarthritis. Novel results from this thesis showed that: (1) larger knee loads predicted cartilage loss over 2.5 years in obese individuals with knee osteoarthritis but not in persons of normal weight or overweight; (2) among women with knee osteoarthritis with lower self-efficacy (or confidence), lesser knee muscle capacity (strength, power) was an important predictor of declining stair-climbing performance over 2 years; and (3) clinical interventions that can positively alter knee biomechanics include weight loss, knee muscle strengthening, as well as specific knee surgery and alterations during walking to reduce knee loads. Interventions for knee osteoarthritis should target biomechanical and clinical outcomes simultaneously.