RESUMO
The aims of this study were to describe age- and sex-related differences in total body skeletal muscle (TB-SM) mass and to determine the variance explained by physical activity (PA). This cross-sectional study included 401 males and 402 females, aged 60-79 years. TB-SM was determined by dual-energy x-ray absorptiometry (DXA) and PA by Baecke questionnaire. Statistical analysis included t test, ANOVAs, Pearson correlations, and multiple regression analysis. TB-SM mass was higher in the youngest age group when compared with the oldest in males and females. Males had greater TB-SM values than females. PA made a significant and positive contribution to the variation in TB-SM, ß = 0.071; p = .016. Sex, height, fat mass, and PA explained 77% of the variance in TB-SM. The oldest cohorts and females had lower TB-SM than the younger cohorts and males. This study suggests that PA exerts a significant role in the explanation of TB-SM.
Assuntos
Exercício Físico/fisiologia , Músculo Esquelético/fisiopatologia , Sarcopenia/fisiopatologia , Absorciometria de Fóton , Idoso , Antropometria , Estudos Transversais , Feminino , Marcha/fisiologia , Humanos , Vida Independente , Masculino , Pessoa de Meia-Idade , Portugal , Fatores Sexuais , Inquéritos e QuestionáriosRESUMO
The purposes of this study were to generate functional-fitness norms for Portuguese older adults, to determine age and sex differences, and to analyze the physical activity-associated variation in functional fitness. The sample was composed of 802 older adults, 401 men and 401 women, age 60-79 yr. Functional fitness was assessed using the Senior Fitness Test. Physical activity level was estimated via the Baecke questionnaire. The P50 values decreased from 60 to 64 to 75 to 79 yr of age. A significant main effect for age group was found in all functional-fitness tests. Men scored significantly better than women in the chair stand, 8-ft up-and-go, and 6-min walk. Women scored significantly better than men in chair sit-and-reach and back scratch. Active participants scored better in functional-fitness tests than their average and nonactive peers. This study showed a decline in functional fitness with age, better performance of men, and increased proficiency in active participants.
Assuntos
Envelhecimento/fisiologia , Exercício Físico/fisiologia , Atividade Motora , Aptidão Física , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Portugal , Características de Residência , Inquéritos e QuestionáriosRESUMO
Faigenbaum, AD, Kraemer, WJ, Blimkie, CJR, Jeffreys, I, Micheli, LJ, Nitka, M, and Rowland, TW. Youth resistance training: Updated position statement paper from the National Strength and Conditioning Association. J Strength Cond Res 23(5): S60-S79, 2009-Current recommendations suggest that school-aged youth should participate daily in 60 minutes or more of moderate to vigorous physical activity that is developmentally appropriate and enjoyable and involves a variety of activities (). Not only is regular physical activity essential for normal growth and development, but also a physically active lifestyle during the pediatric years may help to reduce the risk of developing some chronic diseases later in life (). In addition to aerobic activities such as swimming and bicycling, research increasingly indicates that resistance training can offer unique benefits for children and adolescents when appropriately prescribed and supervised (). The qualified acceptance of youth resistance training by medical, fitness, and sport organizations is becoming universal ().Nowadays, comprehensive school-based programs are specifically designed to enhance health-related components of physical fitness, which include muscular strength (). In addition, the health club and sport conditioning industry is getting more involved in the youth fitness market. In the U.S.A., the number of health club members between the ages of 6 and 17 years continues to increase () and a growing number of private sport conditioning centers now cater to young athletes. Thus, as more children and adolescents resistance train in schools, health clubs, and sport training centers, it is imperative to determine safe, effective, and enjoyable practices by which resistance training can improve the health, fitness, and sports performance of younger populations.The National Strength and Conditioning Association (NSCA) recognizes and supports the premise that many of the benefits associated with adult resistance training programs are attainable by children and adolescents who follow age-specific resistance training guidelines. The NSCA published the first position statement paper on youth resistance training in 1985 () and revised this statement in 1996 (). The purpose of the present report is to update and clarify the 1996 recommendations on 4 major areas of importance. These topics include (a) the potential risks and concerns associated with youth resistance training, (b) the potential health and fitness benefits of youth resistance training, (c) the types and amount of resistance training needed by healthy children and adolescents, and (d) program design considerations for optimizing long-term training adaptations. The NSCA based this position statement paper on a comprehensive analysis of the pertinent scientific evidence regarding the anatomical, physiological, and psychosocial effects of youth resistance training. An expert panel of exercise scientists, physicians, and health/physical education teachers with clinical, practical, and research expertise regarding issues related to pediatric exercise science, sports medicine, and resistance training contributed to this statement. The NSCA Research Committee reviewed this report before the formal endorsement by the NSCA.For the purpose of this article, the term children refers to boys and girls who have not yet developed secondary sex characteristics (approximately up to the age of 11 years in girls and 13 years in boys; Tanner stages 1 and 2 of sexual maturation). This period of development is referred to as preadolescence. The term adolescence refers to a period between childhood and adulthood and includes girls aged 12-18 years and boys aged 14-18 years (Tanner stages 3 and 4 of sexual maturation). The terms youth and young athletes are broadly defined in this report to include both children and adolescents.By definition, the term resistance training refers to a specialized method of conditioning, which involves the progressive use of a wide range of resistive loads and a variety of training modalities designed to enhance health, fitness, and sports performance. Although the term resistance training, strength training, and weight training are sometimes used synonymously, the term resistance training encompasses a broader range of training modalities and a wider variety of training goals. The term weightlifting refers to a competitive sport that involves the performance of the snatch and clean and jerk lifts.This article builds on previous recommendations from the NSCA and should serve as the prevailing statement regarding youth resistance training. It is the current position of the NSCA that:
Assuntos
Guias como Assunto , Educação Física e Treinamento/normas , Aptidão Física , Levantamento de Peso , Adolescente , Adulto , Fatores Etários , Traumatismos em Atletas/prevenção & controle , Criança , Proteção da Criança , Feminino , Humanos , Masculino , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Educação Física e Treinamento/tendências , Medição de Risco , Estados Unidos , Adulto JovemRESUMO
The purpose of the present study was to examine genetic and environmental contributions to individual differences in maximal isometric, concentric and eccentric muscle strength and muscle cross-sectional area (MCSA) of the elbow flexors. A generality versus specificity hypothesis was explored to test whether the 4 strength variables share a genetic component or common factors in the environment or whether the genetic/environmental factors are specific for each strength variable. The 4 variables under study were measured in 25 monozygotic and 16 dizygotic male Caucasian twin pairs (22.4 +/- 3.7 years). The multivariate genetic analyses showed that all 4 variables shared a genetic and environmental component, which accounted for 43% and 6% in MCSA (h2 = 81%), 47% and 20% in eccentric (h2 = 65%), 58% and 4% in isometric (h2 = 70%) and 32% and 1% in concentric strength (h2 = 32%) respectively. The remaining variation was accounted for by contraction type specific and muscle cross-sectional area specific genetic and environmental effects, which accounted for 38% and 14% in MCSA, 18% and 15% in eccentric, 12% and 26% in isometric and 0% and 67% in concentric strength respectively. This exploratory multivariate study suggests shared pleiotropic gene action for MCSA, eccentric, isometric and concentric strength, with a moderate to high genetic contribution to the variability of these characteristics.
Assuntos
Contração Isométrica/genética , Força Muscular/genética , Gêmeos Dizigóticos/genética , Gêmeos Monozigóticos/genética , Adolescente , Adulto , Braço , Cotovelo , Humanos , Masculino , Análise MultivariadaRESUMO
The removal of regular weight-bearing activity generates a skeletal adaptive response in both humans and animals, resulting in a loss of bone mineral. Human models of disuse osteoporosis, namely bed rest, spinal cord injury and exposure to micro-gravity demonstrate the negative calcium balance, alterations in biochemical markers of bone turnover and resultant loss of bone mineral in the lower limbs that occurs with reduced weight-bearing loading. The site-specific nature of the bone response is consistent in all models of disuse; however, the magnitude of the skeletal adaptive response may differ across models. It is important to understand the various manifestations of disuse osteoporosis, particularly when extrapolating knowledge gained from research using one model and applying it to another. In rats, hindlimb unloading and exposure to micro-gravity also result in a significant bone response. Bone mineral is lost, and changes in calcium metabolism and biochemical markers of bone turnover similar to humans are noted. Restoration of bone mineral that has been lost because of a period of reduced weight bearing may be restored upon return to normal activity; however, the recovery may not be complete and/or may take longer than the time course of the original bone loss. Fluid shear stress and altered cytokine activity may be mechanistic features of disuse osteoporosis. Current literature for the most common human and animal models of disuse osteoporosis has been reviewed, and the bone responses across models compared.
Assuntos
Densidade Óssea , Osso e Ossos/fisiopatologia , Modelos Animais de Doenças , Osteoporose/fisiopatologia , Suporte de Carga , Adaptação Fisiológica , Animais , Repouso em Cama/efeitos adversos , Cães , Exercício Físico , Humanos , Ratos , Recuperação de Função Fisiológica , Estresse Mecânico , Simulação de Ausência de PesoRESUMO
Shuttle tests are simple, inexpensive field tests that have been used to estimate the cardiorespiratory status of children. It has yet to be validated in children with CF. The aim of this study was to assess the reproducibility and criterion validity of shuttle tests in children with cystic fibrosis (CF). Ninety-three CF patients aged 6 to 16 years of age with a wide range of disease severity performed the study. The 10-m shuttle test was used for children 7 years of age and younger and those deemed too chronically ill by their physicians to perform the longer test (n = 35.) All other children performed the 20-m shuttle test (n = 58). Reproducibility and criterion validity were assessed for each child over a two week period. Gas analysis was performed throughout testing using a polargraphic gas analyzer. The 10-m shuttle tests were reproducible (mean difference between tests VO(2) 2.41 mL/kg/min, CI 3.46,-0.18) and the difference from treadmill testing was not statistically significant (mean difference VO(2) 5.30 mL/kg/min, CI-7.46, 1.18). The 20-m shuttle tests were reproducible (mean difference between tests VO(2) 2.07 mL/kg/min, CI-3.90,0.60) and the difference from treadmill testing was not statistically significant (mean difference VO(2) 3.50 mL/kg/min, CI-4.90, 1.60). We conclude that when formal exercise testing with treadmill or cycle ergometer cannot be performed, the shuttle tests provide a reproducible and valid alternative.
Assuntos
Fibrose Cística/diagnóstico , Fibrose Cística/fisiopatologia , Teste de Esforço , Tolerância ao Exercício/fisiologia , Doença Cardiopulmonar/diagnóstico , Doença Cardiopulmonar/fisiopatologia , Adolescente , Fatores Etários , Criança , Pré-Escolar , Fibrose Cística/complicações , Humanos , Doença Cardiopulmonar/etiologia , Reprodutibilidade dos Testes , Corrida/fisiologia , Índice de Gravidade de Doença , Espirometria , Caminhada/fisiologiaRESUMO
PURPOSE: This study investigated the influence of different exercise types and differences in anatomical distribution of mechanical loading patterns on bone mineral density (BMD) in elite female cyclists, runners, swimmers, triathletes, and controls (N = 15 per group). Associations between leg strength and BMD were also examined. METHODS: Areal BMD (g x cm(-2)) was assessed by duel-energy x-ray absorptiometry (DXA) (total body (TB), lumbar spine (LS), femoral neck (FN), legs, and arms). Right knee flexion and extension strength was measured using a Cybex Norm isokinetic dynamometer at 60 degrees x s(-1). RESULTS: Runners had significantly higher unadjusted TB, LS, FN, and leg BMD than controls (P < 0.05); higher TB, FN, and leg BMD than swimmers (P < 0.05); and greater leg BMD than cyclists (P < 0.05). Absolute knee extension strength was significantly (P < 0.01) correlated (0.33 < or = r < or = 0.44) with TB, FN, LS, and leg BMD for all groups combined. Weaker but still significant correlations (0.28 < or = r < or = 0.33) existed for normalized (per leg lean tissue mass) knee extension strength and all BMD sites, except FN BMD. There were no significant correlations between absolute or normalized knee flexion strength and any of the BMD variables. Absolute knee extension strength was entered as the second independent predictor for LS and leg BMD in stepwise multiple linear regression analysis (MLRA), accounting for increments of 4% and 12%, respectively, in total explained variation. CONCLUSION: We conclude that running, a weight bearing exercise, is associated with larger site-specific BMD than swimming or cycling, that the generalized anatomical distribution of loads in triathlon appears not to significantly enhance total body BMD status, and that knee extension strength is only a weak correlate and independent predictor of BMD in adolescent females.
Assuntos
Adolescente/fisiologia , Densidade Óssea/fisiologia , Músculo Esquelético/fisiologia , Educação Física e Treinamento/métodos , Esportes/fisiologia , Braço/fisiologia , Ciclismo/fisiologia , Feminino , Colo do Fêmur/fisiologia , Humanos , Perna (Membro)/fisiologia , Vértebras Lombares/fisiologia , Valores de Referência , Corrida/fisiologia , Natação/fisiologiaRESUMO
PURPOSE: Right-leg mid-femur geometry and biomechanical indices of bone strength were compared among elite cyclists (CYC), runners (RUN), swimmers (SWIM), triathletes (TRI), and controls (C)-10 subjects per group. METHODS: Bone cross-sectional areas (CSA), volumes (Vol), and cross-sectional moments of inertia (CSMI) were assessed by magnetic resonance imaging (MRI), and cortical volumetric bone density (volBMD) was determined as the quotient of DXA-derived bone mineral content (BMC) and MRI-derived cortical bone volume. Bone strength index (BSI) was calculated as the product of cortical volBMD and CSMI. RESULTS: RUN had higher (P < 0.05) size- (femur length and body mass) adjusted (ANCOVA) cortical CSA than C, SWIM, and CYC; and higher size, age, and years of sport-specific training- (YST) adjusted cortical CSA than SWIM and CYC. TRI had higher (P < 0.05) size-adjusted CSA than SWIM. SWIM and CYC had significantly larger (P < 0.05) size-adjusted medullary cavity CSA than RUN and TRI, and the difference between CYC and RUN persisted after additional adjustment for age and YST. RUN had significantly (P < 0.05) greater size-adjusted CSMI and BSI than C, SWIM, and CYC; and higher size, age, and YST-adjusted CSMI and BSI than SWIM and CYC. Mid-femur areal bone mineral density (BMD) was significantly (P < 0.05) higher for RUN compared with CYC only, but there were no other differences among groups for BMC, bone volumes, or volumetric total or cortical BMD. CONCLUSIONS: Running, a weight-bearing exercise, is associated with more favorable geometric and biomechanical characteristics in relation to bone strength, compared with the weight supported activities of swimming and cycling. Differences may reflect skeletal adaptations to the specific mechanical-loading patterns inherent in these sports.
Assuntos
Fêmur/anatomia & histologia , Fêmur/fisiologia , Esportes/fisiologia , Adaptação Fisiológica/fisiologia , Adolescente , Fenômenos Biomecânicos , Densidade Óssea , Feminino , Fêmur/metabolismo , Humanos , Imageamento por Ressonância Magnética , Resistência à Tração , Suporte de Carga/fisiologiaRESUMO
Few studies have explored osteogenic potential of prepubertal populations. We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 prepubertal girls (6 to 10 years) randomly assigned to control (C), low-drop (LD) or high-drop (HD) exercise groups. The latter two groups performed single-leg drop-landings (3 sessions/week-1 and 50 landings/session-1) from 14 cm(LD) and 28 cm(HD) using the nondominant leg. Osteogenic responses were assessed using Dual Energy X-ray Absorptiometry (DXA). Single-leg peak ground-reaction impact forces (PGRIF) in a subsample ranged from 2.5 to 4.4 x body-weight (BW). No differences (p > .05) were observed among groups at baseline for age, stature, lean tissue mass (LTM), leisure time physical activity, or average daily calcium intake. After adjusting for covariates of body mass, fat mass and LTM, no differences were found in bone mineral measures or site-specific bone mineral density (BMD) at the hip and lower leg among exercise or control groups. Combining data from both exercise groups failed to produce differences in bone properties when compared with the control group. No changes were apparent for between-leg differences from baseline to posttraining. In contrast to some reports, our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low-moderate peak ground-reaction impact forces are not osteogenic in the developing prepubertal female skeleton.
Assuntos
Adaptação Fisiológica , Estatura/fisiologia , Exercício Físico/fisiologia , Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Puberdade/fisiologia , Absorciometria de Fóton , Densidade Óssea , Criança , Teste de Esforço , Feminino , Humanos , Estilo de Vida , Atividade Motora , PosturaRESUMO
OBJECTIVES: To review the effects of physical activity on health and behavior outcomes and develop evidence-based recommendations for physical activity in youth. STUDY DESIGN: A systematic literature review identified 850 articles; additional papers were identified by the expert panelists. Articles in the identified outcome areas were reviewed, evaluated and summarized by an expert panelist. The strength of the evidence, conclusions, key issues, and gaps in the evidence were abstracted in a standardized format and presented and discussed by panelists and organizational representatives. RESULTS: Most intervention studies used supervised programs of moderate to vigorous physical activity of 30 to 45 minutes duration 3 to 5 days per week. The panel believed that a greater amount of physical activity would be necessary to achieve similar beneficial effects on health and behavioral outcomes in ordinary daily circumstances (typically intermittent and unsupervised activity). CONCLUSION: School-age youth should participate daily in 60 minutes or more of moderate to vigorous physical activity that is developmentally appropriate, enjoyable, and involves a variety of activities.
Assuntos
Atividade Motora/fisiologia , Logro , Asma/fisiopatologia , Asma/prevenção & controle , Pressão Sanguínea/fisiologia , Índice de Massa Corporal , Densidade Óssea/fisiologia , Criança , Colesterol/sangue , Humanos , Saúde Mental , Síndrome Metabólica/prevenção & controle , Músculo Esquelético/fisiologia , Resistência Física/fisiologia , Aptidão Física/fisiologia , Ferimentos e Lesões/epidemiologiaRESUMO
The pathophysiology of impaired exercise tolerance in patients with cystic fibrosis (CF) is not completely understood. The objective of this study was to compare exercise ability (at clinical and cellular levels) and resting energy expenditure in female athletes with CF compared with matched control subjects. Sixteen subjects and matched control subjects participated in the study. The girls with CF not only had a significantly greater resting energy expenditure (7.6% higher; p<0.05), their habitual daily activity was also significantly greater than that of control subjects (15% greater; p<0.01). Peak aerobic capacity was similar in both groups. However, peak anaerobic power was 20% less (p<0.05) in girls with CF. The 31P magnetic resonance spectroscopy studies demonstrated that there were no differences between the groups at rest, but at 25% total work output the girls with CF were less acidotic (CF, pH 6.99 [0.06]; control subjects, 6.90 [0.05]) and had a significantly lower inorganic phosphorus-to-phosphocreatine ratio (CF, 0.34 [0.07]; control subjects, 0.41 [0.08]). These differences continued to increase to maximal exercise. This study demonstrates that in spite of normal lung function and good nutritional status, females athletes with CF still had significant deficiencies in some measures of fitness and muscle metabolism compared with healthy athletes.
Assuntos
Fibrose Cística/metabolismo , Metabolismo Energético/fisiologia , Tolerância ao Exercício/fisiologia , Músculo Esquelético/metabolismo , Esportes/fisiologia , Adolescente , Fibrose Cística/fisiopatologia , Teste de Esforço , Feminino , Humanos , Espectroscopia de Ressonância Magnética , Músculo Esquelético/fisiopatologia , Descanso/fisiologiaRESUMO
The relationship between fitness and genotype in children with cystic fibrosis (CF) and at least one copy of the DeltaF508 mutation was examined. Genotype was classified according to the second CF mutation. Fitness was measured by peak aerobic capacity (using a modified Bruce protocol during treadmill exercise) and anaerobic power (using the Wingate test on a cycle ergometer). The class of cystic fibrosis transmembrane regulator proteins (CFTR) mutation was statistically related with aerobic capacity, peak anaerobic power, body mass index, lung function (forced expiratory volume in one second), and disease severity as measured by the Shwachman score. Patients with mutations causing defective CFTR production (Class I) or processing (Class II) had a significantly lower peak aerobic capacity (28.6 +/- 4.2 ml/kg/min and 31.7 +/- 5.4 ml/kg/min, respectively) than those with a mutation conferring defective regulation of CFTR (Class III) (43.9 +/- 6.4 ml/kg/min). The peak anaerobic power in subjects with mutations inducing decreased CFTR conduction (Class IV) or CFTR mRNA (Class V), were significantly higher (11.4 +/- 1.7 and 11.6 +/- 1.5 watts/kg, respectively) than children with Class I (9.7 +/- 1.4 watts/kg), Class II (9.8 +/- 1.4 watts/kg), or Class III (10.5 +/- 1.8 watts/kg) mutations. There were no statistically significant differences in the lung function of patients with the different mutations. These results indicate a relationship between CF genotype and some measures of fitness, the mechanisms of which remain to be determined.