Magister Artium (Sport, Recreation and Exercise Science) - MA(SRES) / Hamstrings muscle injury is the most frequent soccer-related injury in amateur and professional soccer players. Despite various interventions, the risk of hamstrings re-injury remains high. Several scientific studies examined the potential risk factors and their contribution to the occurrence of hamstrings injuries in male soccer players. The aim of the study was to investigate the relationship between selected physical characteristics, such as time-to-peak torque, hip abduction peak torque, hamstrings-to-quadriceps strength ratio, and hamstrings flexibility and the occurrence of hamstrings injuries in amateur male soccer players. A prospective, quantitative cross-sectional study design was utilized in this study. A total of 89 amateur male soccer players aged 18-35 years were recruited from the Cape Town Football District to perform functional assessments before injury occurred, which included anthropometric measurements, an evaluation of lower extremity isokinetic muscle strength (both knee and hip) and hamstrings flexibility tests. Instruments used to measure the anthropometric data were a calibrated Seca balance beam scale and stadiometer, a skinfold caliper, a sliding caliper, an anthropometer (All Harpenden, UK) and a metal tape measure. The Biodex Pro System 4 isokinetic dynamometer was used to measure lower extremity isokinetic muscle strength and a goniometer to measure hamstrings flexibility. Descriptive statistics included means and standard deviations, and inferential statistics included Pearson product-moment correlation to determine the relationship between selected physical characteristics and the occurrence of hamstrings injuries. Multivariate logistic regression via the forward stepwise method was utilised to predict potential physical characteristics (risk factors) for hamstrings injury in amateur male soccer players. Statistical significance was a p value of below 0.05. The prevalence of hamstrings injury was 4.3 %, with the multivariate logistic regression analysis indicating that time-to-peak torque was a significant predictor of the occurrence of hamstrings injury (OR = 1; p = 0.027). In conclusion, time-to-peak torque was a significant predictor of the occurrence of hamstrings injury. The players with hamstrings injuries produced a significantly slower time-to-peak torque, which has relevance for soccer players and coaches in addressing this common injury at all levels of competition.

Made available in DSpace on 2014-06-11T19:34:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-30Bitstream added on 2014-06-13T20:05:58Z : No. of bitstreams: 1 cunha_mgs_dr_guara.pdf: 2456684 bytes, checksum: 35c3e64f73a4469232f7849a6e313dfa (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os músculos estriados esqueléticos, através de suas propriedades de contratilidade, extensibilidade e elasticidade, formam o principal motor das articulações nos seres humanos, através da tração exercida no tendão ou na aponeurose. Os músculos controlam, coordenam e realizam os movimentos articulares. A força produzida pelos músculos pode ser estimada através das alavancas realizadas pelo membro, considerando-se o torque de cada força, quando o músculo se contrai, parte da energia desta contração será dissipada na forma de som. A presente pesquisa tem como objetivo principal desenvolver um sistema para avaliar o sinal acústico muscular e comparar com a força produzida em uma célula de carga pela alavanca do membro superior. Os músculos selecionados para esta pesquisa foram os flexores do cotovelo, pela facilidade de acesso e de posicionamento. Foram coletados os sinais acústicos e do esforço realizado de 16 indivíduos de ambos os sexos, sendo 9 do sexo masculino e 7 do sexo feminino, saudáveis, com idade entre 18 e 35 anos, sem histórico de doenças neurológicas, cardiovasculares, não praticantes de atividade física que produzisse a hipertrofia dos músculos flexores do cotovelo. Foi desenvolvido um sistema para avaliação do sinal acústico muscular utilizando como sensor um estetoscópio adaptado com um microfone, simultaneamente à aquisição do torque produzido pelos flexores do cotovelo e avaliado por uma célula de carga. A presente pesquisa permitiu identificar que as principais freqüências acústicas da contração dos flexores do cotovelo estão na faixa de 10 a 15 Hz quando a contração equivale de 75 a 100% da força máxima para o sexo feminino e de 50 a 100 % da força máxima para o sexo masculino e na faixa de 5 a 10 Hz quando a contração equivale de 25 a 50 % da força máxima para o sexo feminino e 25 % da força máxima para o sexo masculino... / Striated skeletal muscles, through their properties of contractility, extensibility and elasticity, are the main driver of the joints in humans, through the traction exerted on the tendon or aponeurosis, muscle control, coordinate and carry out joint movements. The force produced by muscles can be estimated using from the levers held by the member, considering the torque of each force when the muscle contracts, this contraction of the energy is dissipated in the form of sound. The main objective of this research is to develop a system to evaluate the acustic signal and compare it with the muscular force produced in a load cell by the lever of the upper limb. The muscles selected for this research were elbow flexors, because of the easy access and positioning. Acoustic signals were collected and the effort made to 16 individuals of both sexes. We analyzed 9 male and 7 female, healthy and aged between 18 and 35 years old with no history of neurological and cardiovascular disease and not engaged in physical activity that could develop hypertrophy of the elbow flexor muscles. A system was developed for evaluation of the acoustic signal using muscle as a sensor adapted stethoscope with a microphone, simultaneously with the aquisition of the torque produced by the elbow flexor and evaluated by a load cell. This research has identified that the main acoustic frequencies of contraction of the elbow flexors are in the range of 10 to 15 Hz when the contraction equals 75 to 100% of maximum force for females and 50 to 100% of maximum force to males and in the range 50 to 10 Hz when the contraction equals 25 to 50% of maximum force for females and 25% of maximum force for males, as well as the correlation of the acoustic signals of males female with a coefficient less than 4. It was concluded that the acoustic signal muscle has specific characteristics for different levels of intensity of muscle... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:22:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-06-15Bitstream added on 2014-06-13T20:49:25Z : No. of bitstreams: 1 ruas_vda_me_rcla.pdf: 912357 bytes, checksum: 39029679087dd76e4d8e693443be7ed4 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Em muitos programas de condicionamento físico ou de treinamento esportivo, os indivíduos têm de realizar exercícios aeróbios e de força na mesma sessão. No entanto, o treinamento concorrente demanda adaptações específicas para a melhora do rendimento aeróbio e do rendimento de força, e pode, dependendo das condições que forem realizados, comprometerem o rendimento da força. Portanto, os objetivos deste estudo foram: a) Analisar o efeito do exercício aeróbio realizado no ciclismo sobre a força muscular subseqüente, e; b) Verificar se o efeito do exercício aeróbio prévio é dependente do tipo de exercício de força realizado. Doze indivíduos do gênero masculino fisicamente ativos (23 l 3,7 anos, 77,2 l 8,9 kg, 179,3 l 4 cm, 14,34 l 2,99% gordura) executaram 2 testes incrementais até a exaustão em diferentes cadências de pedalada (50 rev.min-1 e 100 rev.min-1) para determinação do LAn, e um protocolo para a determinação da carga equivalente a 10 repetições máximas (10RM) em um aparelho leg-press 45°. Após a realização destes, os mesmos executaram três séries de repetições máximas com a carga de 10RM no leg-press (L) ou três séries de 10 saltos máximos em uma plataforma de saltos (S), nas seguintes condições: 1) Controle (LC e SC); 2) L50 e S50 após a realização de um exercício de 30 minutos no LAn na cadência de 50 rev.min-1; 3) L100 e S100 após a realização de um exercício de 30 minutos no LAn na cadência de 100 rev.min-1. Houve uma redução significante do número de repetições na primeira série nas condições L50 (10 l 1) e L100 (9 l 2) em relação à LC (12 l 2), e na terceira série na condição L100 (6 l 2) comparada à LC (9 l 1). Houve uma redução significante na altura média de saltos... / In several physical conditioning and sports training programs, individuals have to perform aerobic and strength exercises in the same training session. However, the concurrent training demands specific adaptations to the improvement of aerobic and strength performance and, depending of the conditions which they are performed, the strength performance can be compromised. Thus, the purposes of this study were: a) To analyze the effect of aerobic exercise performed in cycling on subsequent muscular strength, and; b) To analyze if the effect of previous aerobic exercise is dependent on the type of the strength exercise. Twelve active males (23 l 3.7 years, 77.17 l 8.86 kg, 179.33 l 4.03 cm, 14.34 l 2.99% body fat) performed 2 incremental tests until exhaustion in different pedal cadences (50 rev.min-1 and 100 rev.min-1) to in order to determine the anaerobic threshold (AT), and a protocol to determine the workload corresponding to 10 maximal repetitions (10RM) in leg press 45°. Then, they performed 3 sets of maximal repetitions with workload of 10RM in leg press (L) or 3 sets of 10 maximal countermovement jumps in a contact plate (S), in the following conditions: 1) Control (LC and SC); 2) L50 and S50 after 30 minutes of cycling at AT and pedal cadence of 50 rev.min-1; 3) L100 and S100 after 30 minutes of cycling at AT and pedal cadence of 100 rev.min-1. There was a significant reduction on the number of repetitions performed in the first set at the conditions L50 (10 l 1) and L100 (9 l 2) in relation to LC (12 l 2), and in the third set at the condition L100 (6 l 2) compared to LC (9 l 1). There was a significant reduction in the mean jump height in the first (29.0 l 4.1 cm) and third (29.1 l 2.9 cm) sets at S50 in relation to SC (32.0 l 3.3 cm and 31.8 l 2.9 cm, respectively). Thus, at these... (Complete abstract click electronic access below)

Orientador: Camila Coelho Greco / Banca: Emerson Franchini / Banca: Mauro Gonçalves / Resumo: Em muitos programas de condicionamento físico ou de treinamento esportivo, os indivíduos têm de realizar exercícios aeróbios e de força na mesma sessão. No entanto, o treinamento concorrente demanda adaptações específicas para a melhora do rendimento aeróbio e do rendimento de força, e pode, dependendo das condições que forem realizados, comprometerem o rendimento da força. Portanto, os objetivos deste estudo foram: a) Analisar o efeito do exercício aeróbio realizado no ciclismo sobre a força muscular subseqüente, e; b) Verificar se o efeito do exercício aeróbio prévio é dependente do tipo de exercício de força realizado. Doze indivíduos do gênero masculino fisicamente ativos (23 l 3,7 anos, 77,2 l 8,9 kg, 179,3 l 4 cm, 14,34 l 2,99% gordura) executaram 2 testes incrementais até a exaustão em diferentes cadências de pedalada (50 rev.min-1 e 100 rev.min-1) para determinação do LAn, e um protocolo para a determinação da carga equivalente a 10 repetições máximas (10RM) em um aparelho leg-press 45°. Após a realização destes, os mesmos executaram três séries de repetições máximas com a carga de 10RM no leg-press (L) ou três séries de 10 saltos máximos em uma plataforma de saltos (S), nas seguintes condições: 1) Controle (LC e SC); 2) L50 e S50 após a realização de um exercício de 30 minutos no LAn na cadência de 50 rev.min-1; 3) L100 e S100 após a realização de um exercício de 30 minutos no LAn na cadência de 100 rev.min-1. Houve uma redução significante do número de repetições na primeira série nas condições L50 (10 l 1) e L100 (9 l 2) em relação à LC (12 l 2), e na terceira série na condição L100 (6 l 2) comparada à LC (9 l 1). Houve uma redução significante na altura média de saltos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In several physical conditioning and sports training programs, individuals have to perform aerobic and strength exercises in the same training session. However, the concurrent training demands specific adaptations to the improvement of aerobic and strength performance and, depending of the conditions which they are performed, the strength performance can be compromised. Thus, the purposes of this study were: a) To analyze the effect of aerobic exercise performed in cycling on subsequent muscular strength, and; b) To analyze if the effect of previous aerobic exercise is dependent on the type of the strength exercise. Twelve active males (23 l 3.7 years, 77.17 l 8.86 kg, 179.33 l 4.03 cm, 14.34 l 2.99% body fat) performed 2 incremental tests until exhaustion in different pedal cadences (50 rev.min-1 and 100 rev.min-1) to in order to determine the anaerobic threshold (AT), and a protocol to determine the workload corresponding to 10 maximal repetitions (10RM) in leg press 45°. Then, they performed 3 sets of maximal repetitions with workload of 10RM in leg press (L) or 3 sets of 10 maximal countermovement jumps in a contact plate (S), in the following conditions: 1) Control (LC and SC); 2) L50 and S50 after 30 minutes of cycling at AT and pedal cadence of 50 rev.min-1; 3) L100 and S100 after 30 minutes of cycling at AT and pedal cadence of 100 rev.min-1. There was a significant reduction on the number of repetitions performed in the first set at the conditions L50 (10 l 1) and L100 (9 l 2) in relation to LC (12 l 2), and in the third set at the condition L100 (6 l 2) compared to LC (9 l 1). There was a significant reduction in the mean jump height in the first (29.0 l 4.1 cm) and third (29.1 l 2.9 cm) sets at S50 in relation to SC (32.0 l 3.3 cm and 31.8 l 2.9 cm, respectively). Thus, at these... (Complete abstract click electronic access below) / Mestre

The purpose of the study was to determine the accuracy of 11 prediction equations in estimating the 1 repetition maximum (1RM) bench press from repetitions completed by collegiate football players (N = 69) using 225 lb. The demographic variables race, age, height, weight, fat-free weight, and percent body fat were measured to determine whether these variables increased the accuracy of the prediction equations; race was the most frequently selected variable in the regression analyses. The validity of the prediction equations was dependent upon the number of repetitions performed, i.e., validity was higher when fewer repetitions were completed. Explained variability of 1RM was slightly higher for all 11 equations when demographic variables were included. A new prediction equation was also developed using the number of repetitions performed and the demographic variables height and fat-free weight.

Muscle weakness is one of the major causes of post-stroke disability. Stroke rehabilitation programs now often incorporate the same type of resistance training that is used for healthy subjects; however, the training effects induced from these training strategies are often limited for stroke patients. An important resistance training principle is that an optimal level of stress is exerted on the neuromuscular system, both during concentric (shortening) and eccentric (lengthening) contractions. One potential problem for post-stroke patients might be difficulties achieving sufficient levels of stress on the neuromuscular system. This problem may be associated with altered muscular function after stroke. In healthy subjects, maximum strength during eccentric contractions is higher than during concentric contractions. In individuals with stroke, this difference in strength is often increased. Moreover, it has also been shown that individuals with stroke exhibit alteration with respect to how the strength varies throughout the range of motion. For example, healthy subjects exhibit a joint specific torque-angle relationship that normally is the same irrespective of contraction mode and contraction velocity. In contrast, individuals with stroke exhibit an overall change of the torque-angle relationship. This change, as described in the literature, consists of a more pronounced strength loss at short muscle length. In individuals with stroke, torque-angle relationships are only partially investigated and so far these relationships have not been analysed using testing protocols that include eccentric, isometric, and concentric modes of contraction.   This thesis investigates the torque-angle relationship of elbow flexors in subjects with stroke during all three modes of contractions – isometric, concentric, and eccentric ­– and the relative loading throughout the range of movement during a resistance exercise. In addition, this thesis studies possible central nervous system mechanisms involved in the control of muscle activation during eccentric and concentric contractions.   The torque-angle relationship during maximum voluntary elbow flexion was examined in stroke subjects (n=11), age-matched healthy subjects (n=11), and young subjects (n=11) during different contraction modes and velocities. In stroke subjects, maximum torque as well as the torque angle relationship was better preserved during eccentric contractions compared to concentric contractions. Furthermore, the relative loading during a resistance exercise at an intensity of 10RM (repetition maximum) was examined. Relative loading throughout the concentric phase of the resistance exercise, expressed as percentage of concentric torque, was found to be similar in all groups. However, relative loading during the eccentric contraction phase, expressed as the percentage of eccentric isokinetic torque, was significantly lower for the stroke group. In addition, when related to isometric maximum voluntary contraction, the loading for the stroke group was significantly lower than for the control groups during both the concentric and eccentric contraction phases. Functional magnetic resonance imaging was used to examine differences between recruited brain regions during the concentric and the eccentric phase of imagined maximum resistance exercise of the elbow flexors (motor imagery) in young healthy subjects (n=18) and in a selected sample of individuals with stroke (n=4). The motor and premotor cortex was less activated during imagined maximum eccentric contractions compared to imagined maximum concentric contraction of elbow flexors. Moreover, BA44 in the ventrolateral prefrontal cortex, a brain area that has been shown to be involved in inhibitory control of motor activity, was additionally recruited during eccentric compared to concentric conditions. This pattern was evident only on the contralesional (the intact hemisphere) in some of the stroke subjects. On the ipsilesional hemisphere, the recruitment in ventrolateral prefrontal cortex was similar for both modes of contractions.    Compared to healthy subjects, the stroke subjects exhibited altered muscular function comprising a specific reduction of torque producing capacity and deviant torque-angle relationship during concentric contractions. Therefore, the relative training load during the resistance exercise at a training intensity of 10RM was lower for subjects with stroke. Furthermore, neuroimaging data indicates that the ventrolateral prefrontal cortex may be involved in a mechanism that modulates cortical motor drive differently depending on mode of the contractions. This might partly be responsible for why it is impossible to fully activate a muscle during eccentric contractions. Moreover, among individuals with stroke, a disturbance of this system could also lie behind the lack of contraction mode-specific modulation of muscle activation that has been found in this population. The altered neuromuscular function evident after a stroke means that stroke victims may find it difficult to supply a sufficient level of stress during traditional resistance exercises to promote adaptation by the neuromuscular system. This insufficiency may partially explain why the increase in strength, in response to conventional resistance training, often has been found to be low among subjects with stroke. / Muskelsvaghet är en av orsakerna till funktionshinder efter stroke. I rehabiliteringsprogram för personer som drabbats av stroke förekommer det numera att styrketräning används i syfte att öka muskelstyrkan. Effekten av styrketräning har dock ofta visat sig vara begränsad. En viktig styrketräningsprincip är att muskulaturen belastas tillräckligt nära maximal styrka under både koncentriska kontraktioner (när man lyfter en vikt) och excentriska kontraktioner (när man kontrollerat sänker en vikt). Ett potentiellt problem skulle kunna vara att personer med stroke inte belastas optimalt under träning på grund av förändrad muskelfunktion. Efter stroke är muskelfunktionen ofta förändrad såtillvida att styrkenedsättningen är mer uttalad under koncentriska kontraktioner. Därutöver har man funnit att styrkenedsättningen är mest uttalad när muskeln är i sitt mest förkortade läge. Detta fenomen har dock inte studerats för alla tre kontraktionstyper, det vill säga excentriska, koncentriska och isometriska kontraktioner, hos personer med stroke.   Denna avhandling undersöker sambandet mellan styrka och ledvinkel över armbågsleden hos personer med stroke under alla tre kontraktionstyper – excentrisk, koncentrisk och isometrisk, samt relativ belastning genom rörelsebanan under en styrketräningsövning. Därutöver undersöker denna avhandling också hjärnans aktiveringsmönster under excentriska och koncentriska kontraktioner.   Sambandet mellan styrka och ledvinkel undersöktes hos personer med stroke (n = 11), åldersmatchade (n = 11) och unga försökspersoner (n = 11). Jämfört med kontrollgrupperna var maximal styrka för personer med stroke mest nedsatt, samt även den oproportionerligt stora styrkenedsättningen vid kort muskelängd som mest uttalad, under koncentriska kontraktioner. Denna avvikelse var minst uttalad vid excentriska kontraktioner. Vidare studerades hur hög belastningen på muskulaturen var i jämförelse med muskelns maximala styrka under en styrketräningsliknande övning för armbågsflexorer vid en träningsintensitet på 10RM. Den uppmätta belastningen under den koncentriska fasen av styrketräningsövningen, uttryckt som procent av den genomsnittliga koncentriska styrkan, var densamma för alla grupperna. Under den excentriska fasen av övningen var dock belastningen, uttryckt som procent av den maximala excentriska styrkan, signifikant lägre för personer med stroke. Träningsbelastningen utgjorde också en lägre andel av den maximala isometriska styrkan för personer med stroke, både under den koncentriska och under den excentriska fasen.   Funktionell magnetresonanstomografi (fMRI) användes för att undersöka hjärnans aktiveringsmönster hos unga försökspersoner (n = 18) och hos individer med stroke (n = 4) när de föreställde sig att de utförde maximal styrketräning för armbågsflexorer (motor imagery). Resultatet visade att primära motorbarken och premotoriska barken var mindre aktiverade när unga friska försökspersonerna föreställde sig utföra maximala excentriska, jämfört med maximala koncentriska kontraktioner. Dessutom var en region i ventrolaterala prefrontala barken, som i tidigare studier visat sig vara inblandat i reglering och hämning av muskelaktivering, mer aktiverade under föreställda excentriska kontraktioner. Detta aktiveringsmönster i den prefrontala barken återfanns dock endast i den icke skadade hjärnhalvan hos personer med stroke.   Jämfört med kontrollgrupperna uppvisade försökspersonerna med stroke en förändrad muskelfunktion som bestod av en specifik nedsättning av styrkan under koncentriska kontraktioner samt också ett mer avvikande samband mellan styrka och ledvinkel under koncentriska kontraktioner. Den relativa belastningen under utförandet av en styrketräningsövning med en intensitet på 10RM var på grund av dessa avvikelser lägre för försökspersoner med stroke. Hjärnavbildnings-studierna indikerade att ventrolaterala prefrontala barken verkar vara involverat i ett kortikalt moduleringssystem som reglerar muskel-aktivering olika beroende på kontraktionstyp under maximala kontraktioner. Detta skulle kunna vara en underliggande mekanism bakom den hittills obesvarade frågan varför det är omöjligt att aktivera muskulaturen maximalt under excentriska kontraktioner. En störning av detta moduleringssystem hos personer med stroke verkar också kunna ligga bakom den förändrade regleringen av muskelaktivering som visat sig förekomma hos personer med stroke. Neuromuskulär funktion efter stroke är förändrad i flera avseenden vilket verkar medföra att muskulaturen inte belastas optimalt under konventionell styrketräning. Detta kan vara en delförklaring till varför styrkeökningen som svar på träning ofta är liten hos personer med stroke.

The purpose of this study was to investigate strength and flexibility development as each is affected by three training programs using two apparatuss the Exer-Genie and the Super-Mini-Gym.

Two different weight training programs were compared to determine which was most effective in improving strength. The experiment was conducted with the bench press, leg press, and sitting press for a period of fifteen weeks.

O objetivo do estudo foi verificar a ocorrência da potencialização pós-ativação (PPA) e o efeito do treinamento de força (TF) sem e com a plataforma vibratória na capacidade de sprints repetidos (CSR). O estudo foi divido em duas partes: a primeira analisou o efeito do TF associado à plataforma vibratória na CSR; e a segunda verificou a ocorrência da PPA na CSR. No primeiro estudo participaram 29 sujeitos, os quais foram divididos em 3 grupos: TF, TF+vibração a 30 Hz e amplitude de 2-4 mm (TF+V30) e TF+vibração a 50 Hz e amplitude de 4-6 mm (TF+V50). Os sujeitos realizaram inicialmente análise da área de secção transversa do quadríceps (ASTQ), teste de uma repetição máxima (1RM) no exercício agachamento e o teste de CSR. Após isso, os sujeitos foram submetidos a 10 semanas de treinamento de força, de acordo com o seu respectivo grupo e, ao final da intervenção, realizaram as mesmas avaliações aplicadas antes das sessões de treinamento. No segundo estudo, 12 jogadores de handebol realizaram teste de 1RM, e em sequência, de maneira aleatória o teste de CSR sem e com a atividade condicionante. A atividade condicionante foi realizada no exercício agachamento e consistiu de cinco séries de uma repetição a 90% de 1RM. O treinamento de força sem e com a vibração aumentou na mesma magnitude a força muscular e a ASTQ. Para o grupo TF+V30, o tempo do melhor sprint (CSRmelhor) melhorou significantemente após as 10 semanas de treinamento, no entanto, sem diferença em relação aos outros grupos. O tempo médio dos sprints (CSRmédio) diminuiu significantemente em todos os grupos. Contudo, para o percentual de decréscimo nos sprints (CSR%dec) apenas foi verificado melhoria no grupo TF em relação à situação pré-treinamento e ao grupo TF+V30 na mesma situação experimental. No segundo estudo foi verificado que o protocolo de PPA melhorou significantemente o CSRmelhor e o CSRmédio, sem alterar o CSR%dec. Dessa forma, conclui-se que o treinamento de força sem e com a plataforma vibratória aumenta a força muscular, a ASTQ e o desempenho na CSR. No entanto, o treinamento de força com a plataforma vibratória não aumentou o desempenho em maior magnitude quando comparado a situação sem este tipo de equipamento. Além disso, o protocolo de PPA melhorou também o desempenho de CSR (CSRmelhor e CSRmédio) em jogadores de handebol. Assim, estratégias para melhorar a força muscular de maneira aguda (PPA) e crônica (TF) aumentam também o desempenho no teste de CSR. / The purpose of this study was to verify the occurrence postactivation potentiation (PAP) and the effect of strength training (ST) with and without vibration platform on repeated sprint ability (RSA). The study was divided in two parts: in the first part, it was analyzed the effect of ST with vibration platform on RSA; and in the second part, it was verified the occurrence of PAP on RSA. Twenty nine subjects participated in the first study, which were divided into 3 groups: ST, ST+vibration at 30 Hz and amplitude of 2-4 mm (ST+V30) and ST+vibration at 50 Hz and amplitude of 4-6 mm (ST+V50). Initially, the quadriceps cross sectional area measurement (QCSA), one repetition maximum (1RM) test on squat exercise and the RSA test were performed. After this, the subjects performed 10 weeks of strength training according to their groups and, at the end of intervention, they were undertook the same evaluations applied before training sessions. In the second study, 12 handball players performed the 1RM test and subsequently they were submitted at random, to the RSA test with and without conditioning activity. The conditioning activity was performed in squat exercise with five sets of one repetition at 90% of 1RM. The strength training with and without vibration platform increased in the same magnitude the muscular strength and QCSA. For ST+V30 group, the best sprint time (RSAbest) was significantly improved after 10 weeks of training, but without difference when compared with other groups. Mean sprint time (RSAmean) was significantly reduced in all groups. However, the percentage of sprint decrement (RSA%dec) only decreased in ST group when compared with the situation before training and the ST+V30 group in the same experimental situation. In the second study, the PAP protocol significantly improved the RSAbest and RSAmean, without change the RSA%dec. From the results, we conclude that the strength training with and without vibration platform improves the strength, QCSA and performance on RSA. However, the strength training with vibration platform did not increase the performance in higher magnitude when compared to the situation without this equipment. Furthermore, PAP protocol improved the RSA performance (RSAbest e RSAmean) in handball players. Thus, strategies to improve muscle strength in acute (PAP) and chronic manner (ST) also increase the performance on RSA test

Introdução: A qualidade de vida de crianças órfãs por aids pode sofrer um impacto negativo no desenvolvimento e crescimento físico. Objetivo: Estimar a força muscular de membros inferiores de crianças órfãs por aids, segundo características sociodemográficas, condições clínicas, atividade física e crescimento corporal. Material e métodos: Estudo transversal realizado com 171 crianças órfãs por aids no município de São Paulo. A variável dependente foi a força muscular, avaliada por meio do teste salto horizontal. As variáveis independentes foram os aspectos sociodemográficos, condições clínicas, atividade física habitual, brincadeiras no lazer, estágio maturacional, estado nutricional e composições corporais. Na análise estatística, foi utilizado o teste “t"de Student e análise de variância ANOVA. Resultados: Crianças órfãs por aids apresentaram menor força muscular em relação a outras crianças brasileiras. Meninos tiveram melhores resultados no teste de força. Crianças cuidadas por um dos pais saltaram mais. Resultados semelhantes foram obtidos para crianças mais velhas e de maior grau de escolaridade. Maior gordura corporal influenciou negativamente o salto horizontal. Crianças com maior circunferência de panturrilha saltaram mais. Conclusão: Os resultados apontam para a necessidade de atenção à saúde das crianças órfãs por aids. / Background: The quality of life of children orphaned by AIDS may suffer a negative impact on their development and growth. Objective: To estimate the muscular strength of low limb in children orphaned by AIDS according to sociodemographic characteristics, clinical conditions, physical activity, and body growth. Methods: A cross-sectional study was conducted with 171 children orphaned by AIDS in the city of São Paulo. The dependent variable was muscular strength, measured by long jump. The independent variables were sociodemographic characteristics, clinical conditions, habitual physical activity, playing during free time, maturation stage, nutrition state, and body composition. The analyses included Student’s t-Test and ANOVA. Results: Children orphaned by AIDS showed less muscular strength when compared to Brazilian children. Boys had better results in the test of strength. Higher jump was observed among children taken care of by a parent, older children and children with a higher educational level. Higher body fat affected negatively the long jump. Children with higher calf circumference performed long jump better. Conclusion: The results highlight the need of addressing attention to the healthcare of children orphaned by AIDS.