Discriminação de desvios de composição corporal de adultos mediante aptidão física em exercícios de força

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Short-term changes in handgrip strength, body composition, and lymphedema induced by breast cancer surgery

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito de um programa de treinamento funcional de curta duração sobre a composição corporal de mulheres na pós-menopausa

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparação da força de preensão palmar e composição corporal entre mulheres mastectomizadas ou não

Introduction: Loss of muscle strength may represent a burden on everyday tasks significantly compromising the quality of life for mastectomy patients. In addition to the reduced strength of the upper limb, has been shown in mastectomy patients and difficulties in reducing grip. Objectives: To analyze the possible differences in grip strength among women undergoing breast cancer surgery and to compare the body composition. Methods: In the control group (CG n = 46) women participated in the community of FCT / UNESP aged 35 to 70 years without acute orthopedic pathologies. In the experimental group (EG n = 49) participated in women undergoing surgery for breast cancer, without bilateral lymphedema and independent of time and type of surgery. Were evaluated by dynamometer, by Dual Energy X-ray absorptiometry (DEXA) and physical assessment. Results: We observed significant differences in grip strength (p = 0.000), when the group after mastectomy compared with the control group and the radical mastectomy surgery left and quandrandectomia left (p = 0.004). Regarding the presence of lymphedema, statistical difference was observed in the composition of lean mass and trunk fat (p = 0.05). Conclusion: The results of this study suggest that the experimental group are lower grip strength and trunk lean body mass when compared with the control group. The experimental group showed higher values of fat mass when there was presence of lymphedema

Relações entre força muscular e composição corporal e regional em idosos

Exercise, in general have the ability to promote health, reduce loss of physical fitness, reduce declines in body composition and prevent disease, and promote improvements in athletic performance, and that's consensual today. Through analysis of body composition and physical fitness, you can diagnose the possible individuals at risk of developing diseases, and fractures caused by falls in the elderly. The DXA tests were used (densitometry by dual beam X-ray) to assess body composition and regional, 1 RM test to evaluate the maximum strength and girth measurements, diameters and skin folds in order to analyze the balance of power muscle with both body composition as regional. The results showed that the variance in bone mass between older content related to the change in the maximum muscular strength of the upper and lower limbs, but the force values are not related to increased muscle mass. The development of muscle strength fulfills a dual function in aging which is to maintain or reduce the rate of loss of lean body mass, and also so the body bone health

Anthropometric profile and upper-limbs strength of bull rider s competitors

A força de preensão manual tem sido relatada como determinante no desempenho de empunhadura em modalidades como lutas e escalada. Este estudo teve por propósito avaliar a aptidão de força isotônica máxima e de preensão manual em praticantes e não praticantes de montaria em touros, a fim de obter parâmetros de referência desta população. Foram avaliados 20 sujeitos em dois grupos, sendo 10 classificados como atletas de montaria e 10 não-atletas. A avaliação da força de preensão manual foi realizada em dinamômetro em posição convencional (DP) e específica (DE), com ambas as mãos (D e E). A força isotônica máxima foi determinada pelo teste de uma repetição máxima (1RM) e também foram obtidas medidas de circunferência dos segmentos, bem como a composição corporal por protocolo de dobras cutâneas. Os valores das variáveis foram comparados pelo teste-t (ρ ≤ 0,05) para dados independentes. As relações entre os valores de força e características antropométricas foram traçadas pelo coeficiente de Pearson. Os resultados para AMT em DPD (43.8±6.8 kgf), DPE (39.4±7.7 kgf), DED (44.9±5.6 kgf) e DEE (39.8±8.3 kgf) comparados aos apresentados por n-AMT em DPD (47.0±3.0 kgf), DPE (42.2±6.1 kgf), DED (49.2±1.5 kgf) e DEE (46.2±4.1 kgf) apresentaram diferenças apenas para DED e DEE. A força nos testes de 1RM (supino reto: 73.2±12.0 kg e 82.0±12.0 kg; rosca direta: 45.2±8.9 kg e 43.8±8.9 kg; tríceps pulley: 67.0±6.3 kg e 72.0±6.3 kg; e puxada posterior: 73.5±8.5 kg e 73.7±7.5 kg) não mostram diferenças entre os grupos. A influência sobre a dinamometria apresenta-se diferente entre os grupos, sendo relevante a força de flexão do cotovelo em AMT e a antropometria e força isotônica para n-AMT. Conclui-se que as características morfo-funcionais de membros superiores não demandam especificidade à montaria em touros.

Efeitos das antocianinas, ácidos hidroxinâmicos e vitamina C sobre a biometria, composição corporal e qualidade óssea de ratos Wistar

Pós-graduação em Medicina Veterinária - FCAV

Avaliação da composição corporal e consumo de macronutrientes de mulheres atletas do judô

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de força muscular e composição corporal de mulheres com Síndrome dos Ovários Policísticos

OBJETIVOS: Comparar os parâmetros metabólicos, a composição corporal e a força muscular de mulheres com Síndrome dos Ovários Policísticos (SOP) em relação a mulheres com ciclos menstruais ovulatórios. MÉTODOS: Estudo caso-controle com 27 mulheres com SOP e 28 mulheres controles com ciclos ovulatórios, com idade entre 18 e 37 anos, índice de massa corpórea entre 18 e 39,9 kg/m², que não praticassem atividade física regular. Níveis séricos de testosterona, androstenediona, prolactina, globulina carreadora dos hormônios sexuais (SHBG), insulina e glicemia foram avaliados. Índice de andrógeno livre (FAI) e resistência insulina (por HOMA) foram calculados. As voluntárias submetidas avaliação de composição corporal por dobras cutâneas e absorciometria de raio X de dupla energia (DEXA) e testes de força muscular máxima de 1-RM em três exercícios após procedimento de familiarização e de força isométrica de preensão manual. RESULTADOS: Os níveis de testosterona foram mais elevados no grupo SOP em relação ao CO (68,0±20,2 versus 58,2±12,8 ng/dL; p=0,02), assim como o FAI (282,5±223,8 versus 127,0±77,2; p=0,01), a insulina (8,4±7,0 versus 4,0±2,7 uIU/mL; p=0,01), e o HOMA (2,3±2,3 versus1,0±0,8; p=0,01). O SBHG foi inferior no grupo SOP comparado ao controle (52,5±43,3 versus 65,1±27,4 nmol/L; p=0,04). Não foram observadas diferenças significativas na composição corporal com os métodos propostos entre os grupos. O grupo SOP apresentou maior força muscular no teste de 1-RM nos exercícios supino reto (31,2±4,75 versus 27,8±3,6 kg; p=0,04) e cadeira extensora (27,9±6,2 versus 23,4±4,2 kg; p=0,01), assim como nos testes de força isométrica de preensão manual (5079,6±1035,7 versus 4477,3±69,6 kgf/m²; p=0,04). Ser portadora de SOP foi um preditor independente de aumento de força muscular nos exercícios supino reto (estimativa (E)=2,7) (p=0,04) e cadeira extensora (E=3,5) (p=0,04). Assim como o IMC no exercício de força isométrica de preensão manual do membro dominante (E=72,2) (p<0,01), supino reto (E=0,2) (p=0,02) e rosca direta (E=0,3) (p<0,01). Nenhuma associação foi encontrada entre HOMA-IR e força muscular. CONCLUSÕES: Mulheres com SOP apresentam maior força muscular, sem diferença na composição corporal. A RI não esteve associada ao desempenho da força muscular. Possivelmente, a força muscular pode estar relacionada aos níveis elevados de androgênios nessas mulheres.

El fitness como factor determinante en el riesgo de discapacidad, su relación con la composición corporal y el estado cognitivo en población mayor institucionalizada y de vida independiente = Fitness as a determinant factor in the risk of disability, and its relationship to body composition and cognitive status in institutionalized elderly population and independent living

La condición física, o como mejor se la conoce hoy en día el “fitness”, es una variable que está cobrando gran protagonismo, especialmente desde la perspectiva de la salud. La mejora de la calidad de vida que se ha experimentado en los últimos años en las sociedades desarrolladas, conlleva un aumento de la esperanza de vida, lo que hace que cada vez más personas vivan más años. Este rápido crecimiento de la población mayor de 60 años hace que, un grupo poblacional prácticamente olvidado desde el punto de vista de la investigación científica en el campo de la actividad física y del deporte, cobre gran relevancia, con el fin de poder ayudar a alcanzar el dicho “no se trata de aportar años a la vida sino vida a lo años”. La presente memoria de Tesis Doctoral tiene como principal objetivo valorar los niveles de fitness en población mayor española, además de analizar la relación existente entre el fitness, sus condicionantes y otros aspectos de la salud, tales como la composición corporal y el estado cognitivo. Entendemos que para poder establecer futuras políticas de salud pública en relación a la actividad física y el envejecimiento activo es necesario conocer cuáles son los niveles de partida de la población mayor en España y sus condicionantes. El trabajo está basado en los datos del estudio multicéntrico EXERNET (Estudio Multi-céntrico para la Evaluación de los Niveles de Condición Física y su relación con Estilos de Vida Saludables en población mayor española no institucionalizada), así como en los datos de dos estudios, llevados a cabo en población mayor institucionalizada. Se han analizado un total de 3136 mayores de vida independiente, procedentes de 6 comunidades autónomas, y 153 mayores institucionalizados en residencias de la Comunidad de Madrid. Los principales resultados de esta tesis son los siguientes: a) Fueron establecidos los valores de referencia, así como las curvas de percentiles, para cada uno de los test de fitness, de acuerdo a la edad y al sexo, en población mayor española de vida independiente y no institucionalizada. b) Los varones obtuvieron mejores niveles de fitness que las mujeres, excepto en los test de flexibilidad; existe una tendencia a disminuir la condición física en ambos sexos a medida que la edad aumenta. c) Niveles bajos de fitness funcional fueron asociados con un aumento en la percepción de problemas. d) El nivel mínimo de fitness funcional a partir del cual los mayores perciben problemas en sus actividades de la vida diaria (AVD) es similar en ambos sexos. e) Niveles elevados de fitness fueron asociados con un menor riesgo de sufrir obesidad sarcopénica y con una mejor salud percibida en los mayores. f) Las personas mayores con obesidad sarcopénica tienen menor capacidad funcional que las personas mayores sanas. g) Niveles elevados de fuerza fueron asociados con un mejor estado cognitivo siendo el estado cognitivo la variable que más influye en el deterioro de la fuerza, incluso más que el sexo y la edad. ABSTRACT Fitness is a variable that is gaining in prominence, especially from the health perspective. Improvement of life quality that has been experienced in the last few years in developed countries, leads to an expanded life expectancy, increasing the numbers of people living longer. This population consisting of people of over 60 years, an almost forgotten population group from the point of view of scientific research in the field of physical activity and sport, is becoming increasingly important, with the main aim of helping to achieve the saying “do not only add years to life, but also add life to years”. The principal aim of the current thesis was to assess physical fitness levels in Spanish elderly people, of over 65 years, analyzing relationship between physical fitness, its determinants, and other aspects of health such as body composition and cognitive status. In order to establish further public health policies in relation to physical activity and active ageing it is necessary to identify the starting physical fitness levels of the Spanish population and their determinants. The work is based on data from the EXERNET multi-center study ("Multi-center Study for the Evaluation of Fitness levels and their relationship to Healthy Lifestyles in noninstitutionalized Spanish elderly"), and on data from two studies conducted in institutionalized elderly people: a total of 3136 non-institutionalized elderly, from 6 Regions of Spain, and 153 institutionalized elderly in nursing homes of Madrid. The main outcomes of this thesis are: a) sex- and age-specific physical fitness normative values and percentile curves for independent and non-institutionalized Spanish elderly were established. b) Greater physical fitness was present in the elderly men than in women, except for the flexibility test, and a trend toward decreased physical fitness in both sexes as their age increased. c) Lower levels of functional fitness were associated with increased perceived problems. d) The minimum functional fitness level at which older adults perceive problems in their ADLs, is similar for both sexes e) Higher levels of physical fitness were associated with a reduced risk of suffering sarcopenic obesity and better perceived health among the elderly. f) The elderly with sarcopenic obesity have lower physical functioning than healthy counterparts. g) Higher strength values were associated with better cognitive status with cognitive status being the most influencing variable in strength deterioration even more than sex and age.

Estudio de las dinámicas de pérdida de peso corporal en los programas de ejercicio físico y nutrición = Study of the dynamics of body weight loss in exercise and nutritional programs

Introducción. La obesidad puede definirse como una enfermedad metabólica crónica de origen multifactorial, lo que provoca trastornos o problemas físicos y psicológicos a la persona, con patologías asociadas que limitan la esperanza de vida y deterioran la calidad de la misma, siendo determinante para sus áreas sociales y laborales. Este trastorno metabólico crónico se caracteriza por una acumulación excesiva de energía en el cuerpo en forma de grasa, lo que lleva a un aumento de peso con respecto al valor esperado por sexo, edad y altura. La gestión y el tratamiento de la obesidad tienen objetivos más amplios que la pérdida de peso e incluyen la reducción del riesgo y la mejora de la salud. Estos pueden ser alcanzados por la pérdida modesta de peso (es decir, 10.5% del peso corporal inicial), la mejora del contenido nutricional de la dieta y un modesto incremento en la actividad física y condición física. La dieta es uno de los métodos más populares para perder peso corporal. El ejercicio es otra alternativa para perder peso corporal. El aumento de ejercicio provoca un desequilibrio cuando se mantiene la ingesta calórica. También tiene ventajas, como la mejora del tono muscular, la capacidad cardiovascular, fuerza y flexibilidad, aumenta el metabolismo basal y mejora el sistema inmunológico. Objetivos. El objetivo de esta tesis es contribuir en un estudio de intervención para aclarar la evolución del peso corporal durante una intervención de dieta y ejercicio. Para ello, se evaluaron los efectos de la edad, sexo, índice de masa corporal inicial y el tipo de tratamiento en las tendencias de pérdida de peso. Otro objetivo de la tesis era crear un modelo de regresión lineal múltiple capaz de predecir la pérdida de peso corporal después del periodo de intervención. Y, por último, determinar el efecto sobre la composición corporal (peso corporal, índice de masa corporal, la masa grasa, y la masa libre de grasa) de las diferentes intervenciones basadas en ejercicios (fuerza, resistencia, resistencia combinada con fuerza, y las recomendaciones de actividad física (grupo control)) en combinación con dieta de adultos con sobrepeso y obesidad, después de la intervención, así como los cambios de la composición corporal 3 años más tarde. Diseño de la investigación. Los datos empleados en el análisis de esta tesis son parte del proyecto “Programas de Nutrición y Actividad Física para el tratamiento de la obesidad” (PRONAF). El proyecto PRONAF es un estudio clínico sobre programas de nutrición y actividad física para el sobrepeso y la obesidad, desarrollado en España durante varios años de intervención. Fue diseñado, en parte, para comparar diferentes tipos de intervención, con el objetivo de evaluar su impacto en las dinámicas de pérdida de peso, en personas con sobrepeso y obesidad. Como diseño experimental, el estudio se basó en una restricción calórica, a la que, en algunos casos, se le añadió un protocolo de entrenamiento (fuerza, resistencia, o combinado, en igualdad de volumen e intensidad). Las principales variables para la investigación que comprende esta tesis fueron: el peso corporal y la composición corporal (masa grasa y masa libre de grasa). Conclusiones. En esta tesis, para los programas de pérdida de peso en personas con sobrepeso y obesidad con un 25-30% de la restricción calórica, el peso corporal se redujo significativamente en ambos sexos, sin tener en cuenta la edad y el tipo de tratamiento seguido. Según los resultados del estudio, la pérdida de peso realizada por un individuo (hombre o mujer) durante los seis meses puede ser representada por cualquiera de las cinco funciones (lineal, potencial, exponencial, logarítmica y cuadrática) en ambos sexos, siendo la cuadrática la que tiende a representarlo mejor. Además, se puede concluir que la pérdida de peso corporal se ve afectada por el índice de masa corporal inicial y el sexo, siendo mayor para las personas obesas que para las de sobrepeso, que muestran diferencias entre sexos sólo en la condición de sobrepeso. Además, es posible calcular el peso corporal final de cualquier participante involucrado en una intervención utilizando la metodología del proyecto PRONAF sólo conociendo sus variables iniciales de composición corporal. Además, los cuatro tipos de tratamientos tuvieron resultados similares en cambios en la composición corporal al final del período de intervención, con la única excepción de la masa libre de grasa, siendo los grupos de entrenamiento los que la mantuvieron durante la restricción calórica. Por otro lado, sólo el grupo combinado logra mantener la reducción de la masa grasa (%) 3 años después del final de la intervención. ABSTRACT Introduction. Obesity can be defined as a chronic metabolic disease from a multifactorial origin, which leads to physical and psychological impacts to the person, with associated pathologies that limit the life expectancy and deteriorate the quality of it, being determinant for the social and labor areas of the person. This chronic metabolic disorder is characterized by an excessive accumulation of energy in the body as fat, leading to increased weight relative to the value expected by sex, age and height. The management and treatment of obesity have wider objectives than weight loss alone and include risk reduction and health improvement. These may be achieved by modest weight loss (i.e. 5–10% of initial body weight), improved nutritional content of the diet and modest increases in physical activity and fitness. Weight loss through diet is one of the most popular approaches to lose body weight. Exercise is another alternative to lose body weight. The increase of exercise causes an imbalance when the caloric intake is maintained. It also has advantages such as improved muscle tone, cardiovascular fitness, strength and flexibility, increases the basal metabolism and improves immune system. Objectives. The aim of this thesis is to contribute with an interventional study to clarify the evolution of the body weight during a diet and exercise intervention. For this, the effects of age, sex, initial body mass index and type of treatment on weight loss tendencies were evaluated. Another objective of the thesis was to create a multiple linear regression model able to predict the body weight loss after the intervention period. And, finally, to determine the effect upon body composition (body weight, body mass index, fat mass, and fat-free mass of different exercise-based interventions (strength, endurance, combined endurance and strength, and physical activity recommendations group (control group)) combined with diet in overweight and obese adults, after intervention as well as body composition changes 3 years later. Research Design. The data used in the analysis of this thesis are part of the project "Programs of Nutrition and Physical Activity for the treatment of obesity" (PRONAF). The PRONAF project is a clinical trial program about nutrition and physical activity for overweight and obesity, developed in Spain for several years of intervention. It was designed, in part, to compare different types of intervention, in order to assess their impact on the dynamics of weight loss in overweight and obese people. As experimental design, the study was based on caloric restriction, which, in some cases, added a training protocol (strength, endurance, or combined in equal volume and intensity). The main research variables comprising this thesis were: body weight and body composition outcomes (fat mass and fat-free mass). Conclusions. In this thesis, for weight loss programs in overweight and obese people with 25-30% of caloric restriction, the body weight was significantly decreased in both sexes, regardless the age and type of followed treatment. According to the results of the study, the weight loss performed by an individual (male or female) during six months can be represented by any of the five functions (linear, power law, exponential, logarithmic and quadratic) in both sexes, being the quadratic one which tends to represent it better. In addition, it can be concluded that the body weight loss is affected by the initial body mass index and sex condition, being greater for the obese people than for the overweight one, showing differences between sexes only in the overweight condition. Moreover, it is possible to calculate the final body weight of any participant engaged in an intervention using the PRONAF Project methodology only knowing their initial body composition variables. Furthermore, the four types of treatments had similar results on body composition changes at the end of the intervention period, with the only exception of fat-free mass, being the training groups the ones that maintained it during the caloric restriction. On the other hand, only the combined group achieved to maintain the fat mass (%) reduced 3 years after the end of the intervention.

Effects of whole body vibration on strength and jumping performance in volleyball and beach volleyball players

The primary aim of this study was to examine the effects of 6-week strength training with whole body vibration (WBV) on leg strength and jumping performance in volleyball and beach volleyball players. Twenty-three sub-elite male volleyball (VB; n=12) and beach volleyball players (BVB; n=11) aged 21.2±3.0 years were divided into two groups and subjected to 6 weeks of strength training (three one-hour sessions per week): (I) 12 players (6 VB and 6 BVB players) underwent training with WBV (30-40 Hz, 1.7-2.5 mm, 3.0-5.7 g), and (II) 11 players (6 VB and 5 BVB players) underwent traditional strength training. Squat jump (SJ) and countermovement squat jump (CMJ) measurements by the Ergo Tester contact platform and maximum leg press test (1RM) were conducted. Three-factor (2 time x 2 WBV use x 2 discipline) analysis of variance for SJ, CMJ and 1RM revealed a significant time main effect (p<0.001), a WBV use effect (p<0.001) and a discipline effect (p<0.001). Significantly greater improvements in the SJ (p<0.001) and CMJ (p<0.001) and in 1RM (p<0.001) were found in the WBV training groups than in traditional training groups. Significant 3-way interaction effects (training, WBV use, discipline kind) were also found for SJ, CMJ and 1RM (p=0.001, p<0.001, p=0.001, respectively). It can be concluded that implementation of 6-week WBV training in routine practice in volleyball and beach volleyball players increases leg strength more and leads to greater improvement in jump performance than traditional strength training, but greater improvements can be expected in beach volleyball players than in volleyball players.

Comparação de diferentes tipos de exercício na composição corporal e força em jovens desportistas do sexo feminino

O estudo pretende comparar o efeito de diferentes tipos de exercício físico na composição corporal e força em jovens desportistas do sexo feminino. A amostra foi constituída por vinte e seis desportistas femininas com idades compreendidas entre os 16 e 21 anos. Previamente ao início do estudo foram sujeitas ao 1º momento de avaliação, e após vinte e quatro semanas realizaram o segundo e ultimo momento de avaliação. Os parâmetros avaliados foram a composição corporal através da técnica de absorciometria radiológica de dupla energia; a força isocinética, nomeadamente os momentos de força (peak-torques) e rácios nos músculos extensores e flexores do joelho; a potência muscular nos membros inferiores através dos saltos verticais Squat jump e Countermovement jump. Posteriormente foram separadas em quatro grupos, grupo natação e exercício vibratório (NAT EV; n= 6), grupo natação (NAT; n=6), grupo futsal (FUTS; n= 6) e o grupo de controlo (CONT; n= 8). O grupo (NAT/EV), participou num programa de exercício vibratório (EV), três sessões por semana complementar ao treino de natação. O grupo de (NAT) cumpriu o plano de treino correspondente à disciplina, o grupo de (FUTS) cumpriu o treino referente à respetiva modalidade, o grupo controlo (CONT) realizou somente os exercícios físicos inerentes às aulas de educação física na escola. Resultados: Nas comparações inter grupos, verificou-se no grupo FUTS um aumento de 0,1 (g/m2) ± 0,0 nos valores da DMO-PE, quando comparado com o grupo de CONT, nas comparações intra grupo o grupo de NAT EV registou um acréscimo de 0,1 (g/m2) ± 0,1 nos valores da DMO-TC. Em conclusão, os resultados obtidos sugerem que a modalidade de FUTS promoveu mais alterações na composição corporal, nomeadamente na DMO-PE, no entanto dados conseguidos pelo grupo de NAT EV sugerem que o exercício vibratório poderá influenciar positivamente o incremento da DMO; ABSTRACT: The objective of this study was to compare the effect of different types of exercise on body composition and strength in young female athletes. The sample consisted of twenty-six female athletes aged between 16 and 21. Before the study there was a 1st evaluation point, after twenty-four weeks there was the 2nd and final evaluation. We evaluated body composition through x-ray absorptiometry technique of dual energy, isokinetic strength, including the peak-torques and ratios in the extensor and flexor muscles of the knee; the muscle power in the lower limbs was evaluatated through the vertical jumps Squat jump and countermovement jump. During the study they were separated into four groups, swimming exercise group and vibration (NAT EV; n = 6), swimming group (NAT; n= 6), footsal group (FUTS; n= 6) and control group (CONT; n= 8). The NAT/EV group, participated in a vibrating exercise program (EV), complementary to swimming training, with three sessions per week. The NAT group fulfilled the corresponding swimming workout plan, FUTS group fulfilled the training related to futsal, the CONT group only performed the usual exercises in physical education classes at school. Results: In intergroup comparisons, there was an increase in FUTS group of 0.1 (g / m2) ± 0.0 in the values of MBD-PE, when compared with the CONT group comparisons in intra-group group NAT EV increased by 0.1 (g / m2) ± 0.1 in BMD-TC values. In conclusion, the results suggest that FUTS group promoted more changes in body composition, particularly in BMD-PE, but data obtained by NAT EV group suggest that vibration exercise can positively influence the increase in BMD.

The mechanical strength of phosphates under friction-induced cross-linking

Purpose: In the present study, we consider mechanical properties of phosphate glasses under high temperatureinduced and under friction-induced cross-linking, which enhance the modulus of elasticity. Design/methodology/approach: Two nanomechanical properties are evaluated, the first parameter is the modulus of elasticity (E) (or Young's modulus) and the second parameter is the hardness (H). Zinc meta-, pyro - and orthophosphates were recognized as amorphous-colloidal nanoparticles were synthesized under laboratory conditions and showed antiwear properties in engine oil. Findings: Young's modulus of the phosphate glasses formed under high temperature was in the 60-89 GPa range. For phosphate tribofilm formed under friction hardness and the Young's modulus were in the range of 2-10 GPa and 40-215 GPa, respectively. The degree of cross-linking during friction is provided by internal pressure of about 600 MPa and temperature close to 1000°C enhancing mechanical properties by factor of 3 (see Fig 1). Research limitations/implications: The addition of iron or aluminum ions to phosphate glasses under high temperature - and friction-induced amorphization of zinc metaphosphate and pyrophosphate tends to provide more cross-linking and mechanically stronger structures. Iron and aluminum (FeO4 or AlO4 units), incorporated into phosphate structure as network formers, contribute to the anion network bonding by converting the P=O bonds into bridging oxygen. Future work should consider on development of new of materials prepared by solgel processes, eg., zinc (II)-silicic acid. Originality/value: This paper analyses the friction pressure-induced and temperature–induced the two factors lead phosphate tribofilm glasses to chemically advanced glass structures, which may enhance the wear inhibition. Adding the coordinating ions alters the pressure at which cross-linking occurs and increases the antiwear properties of the surface material significantly.