Sarcopenia (Sc) é uma doença caracterizada por sintomas patológicos sem causas específicas que acomete parte dos idosos. A Sc promove reduções na massa muscular (MM) e força muscular (FM), com sérios impactos funcionais e motores. A força de preensão manual (FPM) utilizada para diagnosticar Sc não é representativa da FM global, especialmente para FM de membros inferiores (MMII), quando idosos passam por intervenção com treinamento de FM. Embora utilizada para definir a Sc, FM é considerada de forma absoluta ou relativizada pela massa corporal (MC), cuja relação nem sempre é linear. Assim, o objetivo deste estudo foi estabelecer parâmetros válidos para diagnóstico da Sc, a partir de diferentes expressões da FM de MMII em idosos. Uma amostra de 98 idosos fisicamente independentes foi medida pela absorciometria radiológia de dupla energia (DXA) para determinação do Tecido Mole Magro apendicular. Os idosos foram classificados por sexo e Sc (1=Sc; 0=não Sc), segundo os critérios do European Working Group on Sarcopenia in Older People (EWGSOP). A FM de extensão de joelhos (FMEJ) isocinética determinada a 60º/s (Biodex, System 4 Pro), foi considerada como FM referencial (FMEJTorquePico-60°/s), e a FMEJ Estimada em cadeira extensora (CMáxEstFMEJcad-ext), em protocolo de repetição máxima. Análise descritiva com medidas de tendência central foi utilizada para caracterização da amostra. A validação da FMEJ Estimada foi testada por correlação com a FMEJ de referência. Os valores de CMáxEstFMEJcad-ext foram relativizados pela massa corporal (FMEJ/MC) e por ajustes alométricos (FMEJ/MCb), onde b é o expoente gerado por regressão log-linear entre FMEJ e MC. Para determinar um modelo explicativo da Sc a partir de cada expressão da CMáxEstFMEJcad-ext (absoluta, FMEJ/MC e FMEJ/MCb) foi empregada a regressão logística simples. Os pontos de corte para Sc a partir da CMáxEstFMEJcad-ext foram definidos pela curva Característica de Operação do Receptor (ROC) e localizados pelo índice de Youden. As análises foram realizadas no Statistical Product and Service Solutions (SPSS) 20.0 e MedCalc 15.2 com níveis de significância previamente estabelecidos (?=0,05). Os resultados indicaram que a Sc esteve presente em 12,9% dos homens e 9,0% das mulheres. Houve alta correlação entre a medida de FMEJ de referência e a Estimada (r=0,81), mesmo entre idosos com Sc (r=0,72). Os expoentes b obtidos foram de 0,96 e 0,70 para homens e mulheres, respectivamente. Na regressão logística, as expressões relativas (FMEJ/MC e FMEJ/MCb) não explicaram a probabilidade para ocorrência da Sc em nenhum dos sexos. Somente a CMáxEstFMEJcad-ext absoluta explicou a chance para homens (?2=3,869; p=0,049) e mulheres (?2=4,145; p=0,042). A área abaixo da curva foi elevada (AUC>0,70), com pontos de corte de 65,0kg para homens e 34,9kg para mulheres. Conclui-se que a CMáxEstFMEJcad-ext é uma medida válida para monitorar Sc como parâmetro de FM em idosos, mesmo quando apresentam Sc. Os limiares de carga (kg) propostos como pontos de corte podem ser usados em um simples teste FMEJ da prática clínica profissional. Além disso, tem boa sensibilidade para monitorar a distância do ponto corte para Sc, o que não é possível com o modelo dicotômico do EWGSOP / Sarcopenia (Sc) is a disease characterized by pathological symptoms without specific causes that affects part of the elderly. Sc promotes reductions in muscle mass (MM) and muscle strength (MS), with serious functional and motor impacts. The handgrip strength (HS) used to diagnose Sc is not representative of global MS, especially for lower limb (LL) MS, when the elderly go through an intervention with MS training. Although used to define Sc, MS is considered absolutely or relativized by body mass (BM), whose relationship is not always linear. Thus, the objective of this study was to establish valid parameters for the diagnosis of Sc, from different MS expressions of LL in the elderly. A sample of 98 physically independent elderly subjects was measured by dual energy absorptiometry (DXA) to determine appendicular lean soft tissue. The elderly were classified by sex and Sc (1=Sc; 0=not Sc), according to the criteria of the European Working Group on Sarcopenia in Older People (EWGSOP). The isokinetic knee extension MS (KEMS) determined at 60º/s (Biodex, System 4 Pro) was considered as referential (KEMSPeakTork-60°/s), and KEMS Estimated in extensor chair (EstMaxLoadKEMSext-ch), in maximal repetition protocol. Descriptive analysis with measures of central tendency was used to characterize the sample. Validation of the estimated KEMS was tested by correlation with the reference KEMS. The values of EstMaxLoadKEMSext-ch were relativized by body mass (KEMS/BM) and by allometric adjustments (KEMS/BMb), where b is the allometric exponent generated from the log-linear regression between KEMS and BM. To determine an explanatory model of Sc from each expression of EstMaxLoadKEMSext-ch (absolute, KEMS/BM and KEMS/BMb), simple logistic regression was used. The cutoff points for Sc from the EstMaxLoadKEMSext-ch were defined by the Receiver Operating Characteristic (ROC) curve and located by the Youden index. The analyzes were performed in Statistical Product and Service Solutions (SPSS) 20.0 and MedCalc 15.2 with previously established levels of significance (? = 0.05). The results indicated that Sc was present in 12.9% of men and 9.0% of women. There was a high correlation between the reference KEMS and the estimated (r=0.81), even among the elderly with Sc (r=0.72). The exponent b obtained was 0.96 and 0.70 for men and women, respectively. In the logistic regression, the relative expressions (KEMS/BM and KEMS/BMb) did not explain the probability for occurrence of Sc in any of the sexes. Only absolute EstMaxLoadKEMSext-ch explained the chance for males (?2=3,869, p=0.049) and females (?2=4.145, p=0.042). The area below the curve was elevated (AUC>0.70), with cutoff points of 65.0kg for men and 34.9kg for women. It is concluded that the EstMaxLoadKEMSext-ch is a valid measure to monitor Sc as MS parameter in the elderly, even when they present Sc. Load thresholds (kg) proposed as cutoff points can be used in a simple clinical practice test. In addition, it has good sensitivity to monitor the distance from the cut point to MS, which is not possible with the dichotomous model of the EWGSOP

Modelos antropométricos são alternativas mais usadas no estudo da composição corporal (CC) de campo, contudo as propostas bicompartimentais acarretam vieses na sua interpretação. Os objetivos deste estudo foram quantificar, relacionar, comparar e predizer a CC de jovens, considerando idade, maturação e prática esportiva, a partir de uma análise multivariada referenciada por Absortometria de Raios X de Dupla Energia (DXA). Quatrocentos e oito sujeitos de 8 a 18 anos, foram agrupados em esportistas (ES) e não-esportistas (NE), classificados por idade e pico de velocidade de crescimento (PVC). Foram determinadas a massa de gordura (MG), massa óssea (MO) e massa muscular (MM). Das 36 medidas antropométricas iniciais, nove foram as resultantes no modelo utilizado ( n Υ m = n Χ ( r + 1) ( r + 1) β m + n ε m ). O aumento contínuo da CC com a idade, apresentou expressivas variações inter-individuais nas idades próximas ao PVC. As mudanças da CC foram previsíveis e apresentaram velocidades distintas de desenvolvimento, mais coincidentes com as alterações maturacionais. A equação antropométrica multivariada apresentou altos coeficientes de determinação e baixos erros de estimativa. A validação interna do modelo (PRESS = 0,95; 0,93; 0,96), o coeficiente (Q2 = 0,97; 0,97; 0,98) e a confiabilidade (SPRESS = 0,09; 0,01; 0,08), respectivamente para MG, MO e MM, permitiram recomendar sua aplicação para populações com características semelhantes a esta amostra. Não houve diferenças significantes entre ES e NE na MM e MO, mas foram encontradas na MG / Anthropometric models are the most common alternatives used in field body composition (BC) studies, but the bicompartmental models can cause bias in analysis. The objectives of this study was to quantify, relate, compare and predict the BC on youth, considering age, maturation and sport practice from a referenced multivariate analysis by Dual Energy Absorptiometry X-Ray (DXA). Four hundred and eight subjects from 8 to 18 years old were grouped in sport practitioners (SP) and non practitioner (NP), classified by age and peak high velocity (PHV). Fat mass (FM), bone mass (BM) and muscle mass (MM) was determined. From the 36 anthropometric initial measurements, nine resulted in the utilized model ( n Υ m = n Χ ( r + 1) ( r + 1) β m + n ε m ). The continuous increase of the BC related by age expressed inter-individual variations on the PHV ranging ages. The body composition changes were predictable and showed distinct development velocities that coincide with the maturational modifications. The equations showed high determinations coefficients and low estimative errors. Internal validation of the model (PRESS = 0.95; 0.93; 0.96), the coefficient (Q2 = 0.97; 0.97; 0.98) and reliability (SPRESS = 0.09; 0.01; 0.08) respectively for FM, BM and MM allowed to recommend its application for populations with the same characteristics of the subjects in this study. There was no significant differences between SP and NP for MM and BM, but was differences on FM

No description available.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Background: Body composition measures include fat mass (FM), fat free mass (FFM), and percent body fat (%BF), which are markers of health status and disease risk. Accurate body composition assessment is needed to evaluate an individual’s health and the efficacy of treatment strategies. Objective: Compare body composition estimates obtained from the Norland DXA, BodPod®, and iDXA before and after a 12-week exercise intervention. Subjects/setting: Overweight to obese (BMI 25–35 kg/m2) sedentary men and women (n=30) aged 18 to 40 years were recruited from central KY. Main outcome measure: Agreement in FM, FFM, and %BF between Norland DXA, iDXA, and BodPod®. Statistical analysis: Bland Altman plots evaluated mean bias and limits of agreement between iDXA vs Norland DXA, BodPod® vs Norland, and BodPod® vs iDXA. T-tests determined if each mean bias was different from zero. Results: Compared to the iDXA, Norland DXA overestimated BF% and FM at baseline and post intervention (P < 0.01), without differences in FFM (P > 0.05). The BodPod® underestimated BF% and FM and overestimated FFM compared to both DXA machines(all P < 0.01). Conclusion: The Norland and iDXA produce different measures of FM but similar measures of FFM. As well, the BodPod® measures FM and FFM differently than either DXA machine.

These PhD projects represent secondary analyses of data from the ongoing Iowa Fluoride Study (IFS)/Iowa Bone Development Study (IBDS). The aim of this dissertation was to explore the associations between period-specific and cumulative fluoride intakes from birth to age 17, and from birth to age 19 years and bone measures of participants. Also, this dissertation looked into the associations between the clinical presence of dental fluorosis and bone outcomes. Participants have been participating in the IBDS that grew out of the IFS, which is a longitudinal investigation of dietary and non-dietary fluoride exposures, dental fluorosis and dental caries. IFS participants were recruited during 1992-95 from 8 hospital postpartum wards in Iowa, and detailed questionnaires were sent every 1.5-6 months. Data on intakes from water, other beverages, selected foods, dietary fluoride supplements and dentifrice were collected from the questionnaires, and, in combination with water and beverage fluoride levels, combined fluoride was estimated. For the first dissertation project, the association between fluoride intake and peripheral quantitative computed tomography (pQCT)-derived bone outcomes at age 17 were assessed. Participants underwent pQCT of the radius and tibia (XCT-2000) at age 17 years. pQCT results of trabecular bone mineral density (BMD) and bone mineral content (BMC), cortical BMD and BMC, and compression and torsion strength were related to fluoride intake through bivariate and multivariable analyses, adjusting for height, weight, years since peak height velocity, average daily time spent in moderate-to-vigorous intensity physical activity, daily calcium intake, and daily protein intake. P-values < 0.01 were considered statistically significant rather than p< 0.05 due to multiple hypothesis tests. The mean daily fluoride intake estimated by area-under-the-curve (AUC) from birth to 17 years was 0.79 mg (SD = 0.32) for males and 0.70 mg (SD = 0.25) for females. Spearman correlation coefficients between daily fluoride intake and pQCT bone measures were weak (for females r= -0.01 to 0.15 for radius bone outcomes and -0.001 to 0.23 for tibia bone outcomes; for males r= 0.03 to 0.24 for radius bone outcomes and -0.008 to 0.27 for tibia bone outcomes). In sex-specific linear regression analyses for females, partially-adjusted for height, weight, and years since peak height velocity, statistically significant negative associations were detected between all radial bone outcomes and period-specific fluoride intake from 0-8.5 years. Significant positive associations were detected for females between period-specific fluoride intakes from 14-17 years and all tibia bone outcomes, and between period-specific fluoride intakes from 14-17 years and all radius and tibia bone outcomes for males. In the fully-adjusted models, which also included physical activity, protein intake and calcium intake, statistically suggestive negative associations were detected for females during the early fluoride intake period from 0 to 8.5 years and radial cortical bone content and torsion bone strength. A statistically suggestive positive association was found between period-specific fluoride intake from 8.5 to 14 years and torsion bone strength (pSSI) (p< 0.05) for females. For males, statistically significant positive associations were detected between fluoride intake for the period from 14 to 17 years and cortical content and torsion strength (pSSI) at the 0.01 level. The second project examined the associations between period-specific and cumulative fluoride intakes from birth to age 19 years and MDCT-derived bone outcomes at age 19. Age 19 MDCT-derived trabecular and cortical bone micro-architecture scans were acquired at the University of Iowa Comprehensive Lung Imaging Center. MDCT results of the trabecular (volumetric bone mineral density (vBMD), transpose bone mineral density (tBMD), plate trabecula bone mineral density (pBMD), plate width (TS-PW), trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), trabecular network area (Tb.NA)) and cortical (cortical bone porosity (Cb.Poro), cortical thickness (Cb.Th)) bone were related to fluoride intake through bivariate and multivariable analyses, adjusting for height, weight, years since peak height velocity, average daily time spent in moderate-to-vigorous intensity physical activity, Healthy Eating Index (HEI) score, calcium intake and protein intake. P-values < 0.01 were considered statistically significant rather than p< 0.05 due to multiple hypothesis tests. The mean daily fluoride intake estimated by area-under-the-curve (AUC) from birth to 19 years was 0.81 mg (SD = 0.33) for males and 0.69 mg (SD = 0.27) for females. Spearman correlation coefficients between daily fluoride intake and MDCT bone measures were weak (for females r= -0.001 to 0.20 for trabecular bone outcomes and -0.01 to 0.02 for cortical bone outcomes; for males r= -0.003 to 0.16 for trabecular bone outcomes and -0.09 to -0.02 for cortical bone outcomes). In sex-specific partially-adjusted regression analysis adjusted for height, weight, and years since peak height velocity, no statistically significant associations were found for females or males. In the fully-adjusted models, which also included physical activity, HEI score, and protein and calcium intakes, no statistically significant associations were found for either females or males. The third project explored the associations between dental fluorosis score at age 8 and DXA-derived bone outcomes at age 5. DXA bone assessments of the whole body, proximal femur (hip), and lumbar spine were performed at The University of Iowa in the Clinical Research Center (Hologic QDR-2000 DXA unit). The dental fluorosis score was defined as the proportion of zones with definitive or severe fluorosis per person. In the unadjusted associations between bone outcomes and dental fluorosis score, no statistically significant associations were detected for females at the 0.05 level. For males, a statistically significant negative association was found between hip BMD and dental fluorosis score. Sex-specific partial correlation coefficients were estimated between DXA-derived bone outcomes and dental fluorosis score adjusted for height, weight, physical activity, calcium intake and fluoride intake. No statistically significant associations were found for females. For males, a statistically significant negative association was detected between dental fluorosis score and hip BMD. The findings of this dissertation show that life-long intakes from combined sources for adolescents and young adults living in fluoridated areas in the United States were weakly associated with bone measures at age 17 and 19. Furthermore, it was shown that bone outcomes can’t be predicted by the score of dental fluorosis. Fluoride is a mineral that plays an important role in the mineralization of bone and teeth, as well as in dental caries prevention. Numerous professional health organizations endorse the adjusted fluoridation of public water supplies for caries prevention. Results from this dissertation will also help in supporting additional efforts to promote water fluoridation and expand its use, as this dissertation’s outcomes did not demonstrate adverse outcomes related to bone.

Osteoporosis, through its association with age-related fracture, is a major public health concern worldwide. Although osteoporosis was once considered a disease of the elderly, it is now recognized as a condition that has childhood antecedents. The capacity of bone to adapt is the greatest before puberty because of a higher rate of modeling and remodeling. Therefore, the amount of bone gained during childhood and adolescence has the potential to impact lifetime skeletal health. Children who participate in greater amounts of physical activity have greater bone mineral accrual in adolescence as well as a greater peak bone mass in young adulthood. Structured impact loading during growth also positively influences bone parameters. However, the intensity, duration and frequency of loading that is required to elicit skeletal benefits are not well established. Furthermore, although structured physical activity during growth has been hypothesized to delay or prevent the risk of osteoporosis and related fracture later in life there is no clear evidence of a persisting benefit once the loading stimulus has been removed. Therefore, the objective of this thesis was to investigate low-level impact loading during growth and skeletal development as well as to determine the influence of the withdrawal of the loading stimulus on adult bone parameters. Two studies were necessary to realize this objective. The findings should help to determine whether adolescent and adult bone health benefits from structured physical activity during growth. If this is found to be the case then structured gymnastic activity could be promoted as an effective means to optimize adult bone mass, structure and estimated strength.<p> Study 1: The purpose of study one was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts (high level gymnastics exposure) are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics (low level gymnastics exposure). One hundred and sixty three children (30 gymnasts, 61 ex-gymnasts, and 72 non-gymnasts) between 4 and 6 years of age were recruited and measured annually for four years. Total body (TB), lumbar spine (LS) and femoral neck (FN) bone mineral content (BMC) was measured by dual energy x-ray absorptiometry (DXA) at each measurement occasion. Bone mass, density, structure and estimated strength was determined using peripheral quantitative computed tomography (pQCT) at the radius and tibia during the third measurement occasion. Multilevel random effects models were constructed and used to predict differences in TB, LS and FN BMC between groups while controlling for differences in body size, physical activity and diet. Analysis of covariance (covariates of sex, age and height) was used to investigate differences in bone content, density, area, and estimated strength at the radius and tibia. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at the fourth measurement occasion (p<0.05). Gymnasts were also found have 6-25% greater adjusted BMC, volumetric bone mineral density and estimated strength at the distal radius compared to non-gymnasts (p<0.05). These findings suggest that recreational and precompetitive gymnastics participation (low level gymnastics exposure) is associated with greater bone parameters. This is important as beginner gymnastics skills are attainable by most children and do not require a high level of training. Low-level gymnastics skills can easily be integrated into school physical education programs potentially impacting skeletal health.<p> Study 2: The purpose of study 2 was to assess whether the previously reported greater bone mineral content in premenarcheal gymnasts was maintained 10 years after the cessation of participation and removal of the gymnastics loading stimulus. In 1995, thirty elite premenarcheal female gymnasts were recruited into a study investigating the role of high impact physical activity on bone mass in childhood and compared to 30 non-gymnasts. In 2009-2010 gymnasts and non-gymnasts (n=60) were re-contacted and 25 retired gymnasts and 22 non-gymnasts consented to participate. Total body, LS, and FN BMC was assessed at both measurement occasions by DXA. Bone geometric and densitometric parameters were measured by pQCT at the radius and tibia in 2009/10. ANCOVA was used to compare gymnasts and non-gymnasts bone parameters while controlling for differences in age, body composition and maturation. Gymnasts had significantly greater size adjusted TB, LS, and FN BMC (15, 17, and 12%, respectively) at 12 years of age (1995) (p<0.05). At follow-up, retired gymnasts also had significantly greater size adjusted TB, LS, and FN BMC (13, 19 and 13%, respectively) (p<0.05). Furthermore, retired female gymnasts had greater bone area, content and estimated strength at the radius and greater BMC and estimated strength at the tibia compared to non-gymnasts (p<0.05). Premenarcheal gymnasts have bone benefits that were apparent in adulthood after long-term removal of the gymnastics loading stimulus. Low level gymnastics exposure was associated with greater bone parameters in childhood. If these benefits can be maintained, as is suggested in retired competitive gymnasts, recreational gymnastics participation has the potential to positively impact lifetime skeletal health.

Osteoporosis, through its association with age-related fracture, is a major public health concern worldwide. Although osteoporosis was once considered a disease of the elderly, it is now recognized as a condition that has childhood antecedents. The capacity of bone to adapt is the greatest before puberty because of a higher rate of modeling and remodeling. Therefore, the amount of bone gained during childhood and adolescence has the potential to impact lifetime skeletal health. Children who participate in greater amounts of physical activity have greater bone mineral accrual in adolescence as well as a greater peak bone mass in young adulthood. Structured impact loading during growth also positively influences bone parameters. However, the intensity, duration and frequency of loading that is required to elicit skeletal benefits are not well established. Furthermore, although structured physical activity during growth has been hypothesized to delay or prevent the risk of osteoporosis and related fracture later in life there is no clear evidence of a persisting benefit once the loading stimulus has been removed. Therefore, the objective of this thesis was to investigate low-level impact loading during growth and skeletal development as well as to determine the influence of the withdrawal of the loading stimulus on adult bone parameters. Two studies were necessary to realize this objective. The findings should help to determine whether adolescent and adult bone health benefits from structured physical activity during growth. If this is found to be the case then structured gymnastic activity could be promoted as an effective means to optimize adult bone mass, structure and estimated strength.<p> Study 1: The purpose of study one was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts (high level gymnastics exposure) are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics (low level gymnastics exposure). One hundred and sixty three children (30 gymnasts, 61 ex-gymnasts, and 72 non-gymnasts) between 4 and 6 years of age were recruited and measured annually for four years. Total body (TB), lumbar spine (LS) and femoral neck (FN) bone mineral content (BMC) was measured by dual energy x-ray absorptiometry (DXA) at each measurement occasion. Bone mass, density, structure and estimated strength was determined using peripheral quantitative computed tomography (pQCT) at the radius and tibia during the third measurement occasion. Multilevel random effects models were constructed and used to predict differences in TB, LS and FN BMC between groups while controlling for differences in body size, physical activity and diet. Analysis of covariance (covariates of sex, age and height) was used to investigate differences in bone content, density, area, and estimated strength at the radius and tibia. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at the fourth measurement occasion (p<0.05). Gymnasts were also found have 6-25% greater adjusted BMC, volumetric bone mineral density and estimated strength at the distal radius compared to non-gymnasts (p<0.05). These findings suggest that recreational and precompetitive gymnastics participation (low level gymnastics exposure) is associated with greater bone parameters. This is important as beginner gymnastics skills are attainable by most children and do not require a high level of training. Low-level gymnastics skills can easily be integrated into school physical education programs potentially impacting skeletal health.<p> Study 2: The purpose of study 2 was to assess whether the previously reported greater bone mineral content in premenarcheal gymnasts was maintained 10 years after the cessation of participation and removal of the gymnastics loading stimulus. In 1995, thirty elite premenarcheal female gymnasts were recruited into a study investigating the role of high impact physical activity on bone mass in childhood and compared to 30 non-gymnasts. In 2009-2010 gymnasts and non-gymnasts (n=60) were re-contacted and 25 retired gymnasts and 22 non-gymnasts consented to participate. Total body, LS, and FN BMC was assessed at both measurement occasions by DXA. Bone geometric and densitometric parameters were measured by pQCT at the radius and tibia in 2009/10. ANCOVA was used to compare gymnasts and non-gymnasts bone parameters while controlling for differences in age, body composition and maturation. Gymnasts had significantly greater size adjusted TB, LS, and FN BMC (15, 17, and 12%, respectively) at 12 years of age (1995) (p<0.05). At follow-up, retired gymnasts also had significantly greater size adjusted TB, LS, and FN BMC (13, 19 and 13%, respectively) (p<0.05). Furthermore, retired female gymnasts had greater bone area, content and estimated strength at the radius and greater BMC and estimated strength at the tibia compared to non-gymnasts (p<0.05). Premenarcheal gymnasts have bone benefits that were apparent in adulthood after long-term removal of the gymnastics loading stimulus. Low level gymnastics exposure was associated with greater bone parameters in childhood. If these benefits can be maintained, as is suggested in retired competitive gymnasts, recreational gymnastics participation has the potential to positively impact lifetime skeletal health.

PURPOSE: To establish the reliability of anthropometric and dual energy X-ray absorptiometry(DXA) techniques used to assess percent body fat (% BF)in female athletes; to establish limits for detecting the smallest real change in % BF associated with anthropometric and DXA testing;to evaluate the validity of commonly used % BF prediction equations recommended by national certification programs along with equations derived from Multicompartment (MC), and DXA, in female athletes; and to create a new DXA based regression equation for elite female athletes. METHODS:Female athletes aged 17-31 were recruited into the study and participated in the establishment of anthropometric reliability (N=20), DXA reliability (N=32), and /or skinfold validity (N=95) testing. Anthropometric testing consisted of measurements of skinfolds,circumferences, and breadths. DXA measurements were conducted using a GE Lunar Prodigy DXA which served as the criterion measure (% BF DXA). RESULTS: Excellent reliability for both anthropometric sum5 skinfolds (ICC= .997, %TEM=0.9 %) and DXA (ICC =.996, CV =1.13% BF) techniques allows for detection of smallest real differences of 2.2 mm and 721g in summed skinfolds (sum5) and fat mass respectively. The DXA based equation of Ball et al.(2004) displayed the greatest validity of existing equations R=.874, total error (TE) 2.9% BF, and Bland Altman Limits of Agreement -4.7to 6.5 % BF. The newly created regression equation demonstrated a non-linear characteristic and displayed similar predictive ability R= .840, TE 3.0%BF, and Bland Altman Limits of Agreement of -6.1to 6.1 % BF. CONCLUSIONS: Anthropometric equations derived from various criteria yielded dissimilar results. Long utilized popular equations advocated in national accreditation schemes (ACSM, CSEP) show considerable bias compared to modern values obtained by current DXA technology. A new regression equation was created for female Canadian athletes 17-31yrs of age using skinfolds taught in the Canadian national professional certification program (CSEP).

In this thesis, a two-dimensional (2D) finite element (FE) model was developed from the patient’s hip DXA image to evaluate osteoporotic fracture risk. The loading configuration was designed to simulate a lateral fall onto the greater trochanter. Bone inhomogeneous mechanical properties (e.g. Young’s modulus) assigned to the FE model were correlated to bone mineral density captured in DXA image using empirical functions. In-house MATLAB codes were developed to investigate the effects of different factors such as bone mineral density, femoral neck length, neck diameter, neck angle and patient’s body weight on fracture risk. The 2D FE model constructed from DXA image was able to de-termine the factors which affect fracture risk to a greater extent based on the location of femur. The model developed here can be considered as a first attempt for investigating the effects of different parameters on fracture risk using patient specific 2D FE method.