O efeito da potencialização pós-ativação (PPA) tem sido estudado, mas a sua aplicação no desempenho de atletas é muito controversa. Estudos descrevem a possibilidade de que a PPA possa compensar o mecanismo de fadiga, aumentando a taxa de desenvolvimento de força e melhorando a potência muscular. O objetivo deste estudo foi avaliar os efeitos agudos e crônicos de um treinamento pliométrico com e sem indução da PPA na potência muscular de membros inferiores em atletas de voleibol. A amostra foi composta por 16 atletas de voleibol masculino participantes da Superliga Nacional, divididos em grupo pliométrico (GPLIO) e grupo PPA (GPPA). O grupo pliométrico foi submetido a um treinamento de pliometria e o grupo PPA acrescentou ao treinamento pliométrico uma rotina de treinos que estimularam o mecanismo de PPA. O período de treinamento foi de 4 semanas com 2 sessões semanais. Durante a avaliação do pré e pós-treinamento para a determinação dos efeitos crônicos, foi mensurada a potência muscular dos membros inferiores através do salto vertical counter movement jump (CMJ), conforme protocolo sugerido por Bosco (1994), em uma plataforma de força, e contração voluntária máxima para a musculatura da articulação do joelho em um equipamento isocinético. Na avaliação pré e pós-teste para a determinação do efeito agudo, foi utilizado um tapete de contato para obtenção da altura de salto vertical CMJ. Para análise estatística foi utilizado o teste de equações de estimação generalizadas (GEE) no fator tempo e no fator grupo para determinar os efeitos do treinamento em cada grupo (GPLIO e GPPA). Os resultados referente aos efeitos agudos indicam a interação grupo*tempo para o grupo PPA significativa de p<0,001 (38,26 cms / 44,51 cms) do período pré-treinamento para o período de treinamento e de p=0,002 (38,26 cms /44,07 cms) do período pré para o pós treinamento. Ainda observamos que o grupo PPA obteve altura de salto significativamente melhor ao grupo PLIO, tanto no período de treinamento (44,51 cms/35,38cms) como no pós-treinamento pliométrico (44,07cms / 39,32 cms). Quanto aos efeitos crônicos, os resultados demonstraram não haver diferença significativa para as variáveis de torque isocinético. No que diz respeito à altura e potência de salto após o treinamento crônico foi observada diferença significativa nos dois grupos do período pré para o pós-treinamento, não havendo diferença entre os grupos. Concluímos que o treinamento pliométrico com indução de PPA melhora os efeitos agudos do salto vertical, tanto durante o treinamento como até 80 minutos após o treinamento pliométrico. Já no que diz respeito aos efeitos crônicos da indução ou não de PPA no treinamento pliométrico, os resultados indicam não haver diferença significativa no torque isocinético dos músculos extensores do joelho, porém na altura de salto CMJ e potência os resultados indicam que os dois modelos de treinamento têm uma resposta semelhante. / The effect of post-activation potentiation (PPA) has been studied, but its application in the performance of athletes is very controversial. Studies have described the possibility that PPP can compensate for the fatigue mechanism, increasing the rate of strength development and improving muscle power. The objective of this study was to evaluate the acute and chronic effects of a plyometric training with and without PPA induction on lower limb muscle power in volleyball athletes. The sample consisted of 16 male volleyball players participating in the National Superliga, divided into plyometric group (GPLIO) and PPA group (GPPA). The plyometric group underwent a plyometrics training and the PPA group added to the plyometric training a routine of training that stimulated the PPA mechanism. The training period was 4 weeks with 2 weekly sessions. During the pre and post-training evaluation for the determination of the chronic effects, the muscular power of the lower limbs was measured through the vertical jump movement movement (CMJ), according to a protocol suggested by Bosco (1994), on a force platform, And maximal voluntary contraction for the musculature of the knee joint in an isokinetic equipment. In the pre and post-test evaluation for the determination of the acute effect, a contact mat was used to obtain the vertical jump height CMJ. For statistical analysis, the test of generalized estimation equations (GEE) in the time factor and in the group factor was used to determine the effects of the training in each group (GPLIO and GPPA). The results for the acute effects indicate the group*time interaction for the PPA group significant of p<0.001 (38.26 cms / 44.51 cms) of the pre-training period for the training period and p=0.002 (38, 26 cm / 44.07 cm) from the pre and post training period. We also observed that the PPA group had a significantly better jump height in the PLIO group, both in the training period (44.51 cm / 35.38 cm) and in the plyometric training (44.07 cm / 39.32 cm). Regarding the chronic effects, the results showed no significant difference for the isokinetic torque variables. Regarding the height and jumping power after the chronic training, a significant difference was observed in the two groups from the pre-post-training period, with no difference between the groups. We conclude that plyometric training with PPA induction improves the acute effects of vertical jump, both during training and up to 80 minutes after plyometric training. Regarding the chronic effects of PPA or non-PPA induction in plyometric training, the results indicate that there is no significant difference in the isokinetic torque of the knee extensor muscles, but at the height of the CMJ and power jump the results indicate that the two models of Have a similar response.

No description available.

Plyometrics is primarily used by coaches and sport scientists to improve explosive power among athletes who participate in dynamic, high intensity type of sports. One of the plyometric-related training methods that has received attention in recent years, is loaded or resistance (resistive) jump training. Limited research does, however, exist with regard to the benefits and use of this training method as well as in conjunction with other training methods, especially among team sport participants. It is against this background that the research objectives of this study were firstly, to examine the effects of a 4-week combined rugby-conditioning and resisted jump training program compared to a combined rugby-conditioning and normal jump training program, on selected physical, motor ability and anthropometric components of university-level rugby players. The second objective was to examine the acute effects of a resisted compared to a normal jump training session on selected physical and motor ability components of university-level rugby players. Thirty rugby players (age: 19.60 ± 0.79 years) from the first and second u/19 and u/21 rugby teams of a university in South Africa were randomly selected to participate in the first part of study. For the second part of the study thirty senior rugby players (1st and 2nd senior teams) (age: 21.78 ± 1.86 years) of the Rugby Institute at a university in South Africa were randomly selected to participate in the study. For both studies the thirty players were in turn randomly divided into two groups of fifteen players each. One group formed the experimental and the other group the control group. The first objective was tested by subjecting the players to a 4-week combined sport-specific and resisted plyometric training program (experimental group) or a combined sport-specific and normal plyometric training program to investigate the adaptations of body composition, lower body flexibility, explosive leg power, speed, agility and leg strength. After a 10-week period (“wash-out period”) during which subjects continued with their normal rugby-conditioning program, the same testing procedures as before, were executed by following a crossover design. In order to test the second objective of the study players’ body weight and height were firstly measured after which they were subjected to a thorough warm-up, followed by the execution of the flexibility;Vertical Jump Test (VJT); 5-, 10- and 20 m speed tests; the Illinois Agility Run Test (IART) and the 6RM (repetition maximum) Smith Machine Squat Test (6RM-SMST). The experimental group was subject to the resisted jump training session on the Vertimax whereas the control group executed the same exercises on the floor. Directly after the training session each of the players again completed the test battery. After the first week, a crossover design was implemented. Although the overall study (independent t-test and main effect ANOVA) results of the first study suggested that the experimental group experienced more positive changes, especially with regard to the body fat, skeletal mass and somatotype-related anthropometric and flexibility-related measurements, only relaxed upper-arm girth, ectomorphy, left Active-straight-leg-raise-test and the left Modified Thomas Quadriceps Test values showed significant differences (p < 0.05) when the two groups of players were compared. Although the experimental group demonstrated significantly better average scores in the majority of the last-mentioned components, this group experienced a significantly higher reduction in relaxed upper-arm girth due to the conditioning program than the control group. The main effect ANOVA results of the acute study showed that no significant differences were obtained for any of the measured components between an acute resisted and normal jump training session. To conclude, the study revealed that a 4-week combined rugby-conditioning and resisted jump training program (experimental group) did not benefit university-level rugby players significantly more with regard to selected physical, motor ability and anthropometric components than a combined rugby-conditioning and normal jump training program (control group). Furthermore, despite the fact that the acute resisted and normal jump training exercises met all the requirements to produce post-activation potentiation, the study results showed that these exercise sessions did not lead to any significant acute changes in the physical and motor ability components of university-level rugby players. / MA (Sport Science), North-West University, Potchefstroom Campus, 2014

We evaluated anthropometric and performance measures which best predict bone mineral density (BMD) in 54 adolescent girls (14.6��0.5y; 22.7��14.0 months past menarche). BMD for the whole body, femoral neck, greater trochanter, lumbar spine (L2-L4), and mid-femoral shaft was assessed using dual-energy x-ray absorptiometry (DXA) (Hologic QDR 1000/W). Whole body lean mass and fat mass were derived from the whole body scan. Knee extensor strength and leg power were assessed by isokinetic dynamometry and the Wingate Anaerobic Power Test, respectively. Using simple regression, lean mass was significantly correlated with BMD at all bone sites r=.45-.77; p<0.001), and was more highly correlated with BMD at all sites than was body weight. Maximum leg power was also associated with bone mass at all sites (r=.41-.67; p<0.001) while leg strength correlated significantly with all sites (r=.41-.53; p<0.001) except the lumbar spine. Stepwise regression analyses revealed that 59% of the variance in whole body BMD was predicted by lean mass alone. No other variables, including fat mass, height, months past menarche, leg power, or leg strength, contributed additionally to the regression model. Similarly, lean mass was the only predictor of lumbar spine and femoral shaft BMD (R��=.25, R��=.37, respectively), while femoral neck and trochanteric BMD were best predicted by leg power (R��=.38, R��=.36, respectively). In this group of adolescent girls, lean body mass and leg power independently predicted bone mineral density of the whole body, lumbar spine, femoral shaft, and hip, which may suggest an important role for muscle mass development during growth to maximize peak bone density. / Graduation date: 1997

No description available.

Plyometrics is primarily used by coaches and sport scientists to improve explosive power among athletes who participate in dynamic, high intensity type of sports. One of the plyometric-related training methods that has received attention in recent years, is loaded or resistance (resistive) jump training. Limited research does, however, exist with regard to the benefits and use of this training method as well as in conjunction with other training methods, especially among team sport participants. It is against this background that the research objectives of this study were firstly, to examine the effects of a 4-week combined rugby-conditioning and resisted jump training program compared to a combined rugby-conditioning and normal jump training program, on selected physical, motor ability and anthropometric components of university-level rugby players. The second objective was to examine the acute effects of a resisted compared to a normal jump training session on selected physical and motor ability components of university-level rugby players. Thirty rugby players (age: 19.60 ± 0.79 years) from the first and second u/19 and u/21 rugby teams of a university in South Africa were randomly selected to participate in the first part of study. For the second part of the study thirty senior rugby players (1st and 2nd senior teams) (age: 21.78 ± 1.86 years) of the Rugby Institute at a university in South Africa were randomly selected to participate in the study. For both studies the thirty players were in turn randomly divided into two groups of fifteen players each. One group formed the experimental and the other group the control group. The first objective was tested by subjecting the players to a 4-week combined sport-specific and resisted plyometric training program (experimental group) or a combined sport-specific and normal plyometric training program to investigate the adaptations of body composition, lower body flexibility, explosive leg power, speed, agility and leg strength. After a 10-week period (“wash-out period”) during which subjects continued with their normal rugby-conditioning program, the same testing procedures as before, were executed by following a crossover design. In order to test the second objective of the study players’ body weight and height were firstly measured after which they were subjected to a thorough warm-up, followed by the execution of the flexibility;Vertical Jump Test (VJT); 5-, 10- and 20 m speed tests; the Illinois Agility Run Test (IART) and the 6RM (repetition maximum) Smith Machine Squat Test (6RM-SMST). The experimental group was subject to the resisted jump training session on the Vertimax whereas the control group executed the same exercises on the floor. Directly after the training session each of the players again completed the test battery. After the first week, a crossover design was implemented. Although the overall study (independent t-test and main effect ANOVA) results of the first study suggested that the experimental group experienced more positive changes, especially with regard to the body fat, skeletal mass and somatotype-related anthropometric and flexibility-related measurements, only relaxed upper-arm girth, ectomorphy, left Active-straight-leg-raise-test and the left Modified Thomas Quadriceps Test values showed significant differences (p < 0.05) when the two groups of players were compared. Although the experimental group demonstrated significantly better average scores in the majority of the last-mentioned components, this group experienced a significantly higher reduction in relaxed upper-arm girth due to the conditioning program than the control group. The main effect ANOVA results of the acute study showed that no significant differences were obtained for any of the measured components between an acute resisted and normal jump training session. To conclude, the study revealed that a 4-week combined rugby-conditioning and resisted jump training program (experimental group) did not benefit university-level rugby players significantly more with regard to selected physical, motor ability and anthropometric components than a combined rugby-conditioning and normal jump training program (control group). Furthermore, despite the fact that the acute resisted and normal jump training exercises met all the requirements to produce post-activation potentiation, the study results showed that these exercise sessions did not lead to any significant acute changes in the physical and motor ability components of university-level rugby players. / MA (Sport Science), North-West University, Potchefstroom Campus, 2014

This study examined the effects of plyometrics on running economy, performance, and Achilles tendon properties in female distance runners. Seventeen University athletes matched by running economy were randomly assigned to an experimental group that received supplementary plyometrics training (n=9) or a control group that performed run-training only (n=8). Subject attrition led to a final sample of twelve runners (6 experimental, 6 controls). Measurements were made pre-post an 8-week training period. Running economy was measured as oxygen consumption at three submaximal speeds, performance as time to run 3000 meters, and Achilles tendon properties were estimated via ultrasound during ramp, quasi-isometric plantar flexion to maximum on an isokinetic dynamometer. No significant differences were found between the two groups after eight weeks because of poor subject compliance and excessive variability in ultrasound measurements. The results are inconclusive as to the effect of supplementary plyometric training on running economy, performance and Achilles tendon properties.

Thesis (M.S.)--Slippery Rock University of Pennsylvania, 2003. / Includes bibliographical references (leaves 25-26). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (M.S.)--Slippery Rock University of Pennsylvania, 2003. / Includes bibliographical references (leaves 25-26).

Made available in DSpace on 2016-12-06T17:06:59Z (GMT). No. of bitstreams: 1 Elisa DellAntonio.pdf: 1428364 bytes, checksum: 7cad5eef8456a45dd2ee4343be156589 (MD5) Previous issue date: 2014-07-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study aimed to analyze the immersion level effect on kinetic and kinematic characteristics of depth jumps performed on land and in water at different immersion levels. Participants were 26 young male volleyball and track and field athletes (18.2 ± 2.6 years, 1.87 ± 0.1 m in height, and 74.8 ± 9.0 kg body mass). The analyzed variables were the maximum vertical force on the eccentric and concentric sub-phases of contact and landing, the impulse on the eccentric and concentric sub-phases, contact time, eccentric and concentric contact time, and jump flight time. Depth jumps from 0.4 m were executed on land and at four different immersion levels (tibia s midpoint, tibia s lateral condyle, thigh s midpoint and anterior superior iliac spine). A force platform connected to a data acquisition system, a 2-D electrogoniometer and a synchronizing device were used for data collection. Data were processed through specific routines in Scilab 4.1.2 software. Mean values were calculated from three repetitions of each subject in each analyzed condition, and the immersion level effect was analyzed through tests for repeated measures and their respective post-hoc (p <0 05). Results indicate that the higher the immersion level, the lower the values of maximum vertical force on the eccentric and concentric sub-phases of contact and on landing. However, lower levels of immersion (tibia s midpoint and tibia s lateral condyle) were not sufficient to reduce these forces in most cases. Overall, significant reductions of these variables compared with the land execution occurred from the immersion level of the thigh s midpoint. The increase of the immersion level resulted in impulse reduction during eccentric sub-phase and in a longer duration of this phase. However no difference was found between land and water conditions for concentric impulse and contact time. Higher levels of immersion resulted in longer contact time and flight time duration. Therefore, according to these results, due differences between the two environments, aquatic plyometric training may not be adequate to fully replace the plyometric training on land. Despite, aquatic plyometrics present excellent possibilities for training depending on the training purpose, competitive season stage, or the rehabilitation process characteristics. In any of these cases it is necessary to consider the immersion levels, musculoskeletal conditions and individual anthropometrics characteristics. / O objetivo deste estudo foi analisar o efeito da imersão sobre as características cinéticas e cinemáticas de saltos em profundidade realizados no solo e na água com diferentes níveis de imersão. Participaram da pesquisa 26 atletas de voleibol e atletismo, do sexo masculino (18,2 ± 2,6 anos; 1,87 ± 0,1 m de altura; e 74,8 ± 9,0 kg de massa corporal). Foram analisados os valores máximos da força vertical nas subfases excêntrica e concêntrica do contato e na aterrissagem, o impulso nas subfases excêntrica e concêntrica, o tempo de contato, o tempo de contato excêntrico e concêntrico e o tempo de voo durante a execução de saltos em profundidade máximos partindo de 0,4 m no solo e em quatro diferentes níveis de imersão (ponto médio da tíbia, côndilo lateral da tíbia, ponto médio da coxa e espinha ilíaca ântero-superior). Foi utilizada uma plataforma de força conectada a um sistema de aquisição de dados, um eletrogoniômetro 2-D e um sincronizador de sinais. Os dados foram processados através de rotinas específicas no software Scilab 4.1.2. Foram calculados valores médios das três repetições de cada sujeito em cada uma das condições de análise, e o efeito do nível de imersão foi analisado a partir de estatística descritiva e inferencial através de testes para medidas repetidas e seus respectivos post-hoc (p<0,05). Os resultados evidenciam menores valores de força máxima vertical nas subfases excêntrica e concêntrica da queda e na fase de aterrissagem com aumento do nível de imersão. No entanto, na maioria dos casos, níveis baixos de imersão (ponto médio da tíbia e côndilo lateral da tíbia) não foram suficientes para atenuar significativamente estas forças. Em geral, reduções significativas das forças ocorreram a partir do nível de imersão do ponto médio da coxa, em comparação ao solo. O aumento do nível de imersão ocasionou redução no impulso durante a subfase excêntrica e maior duração desta fase. Já para o impulso concêntrico e o tempo de contato concêntrico não foram encontradas diferenças entre a condição solo e as demais. Para o tempo de contato e para o tempo de voo foi constatado que maiores níveis de imersão ocasionam maiores valores dessas variáveis. Os resultados indicam que o treinamento pliométrico no ambiente aquático, devido às diferenças apresentadas entre as execuções dos saltos no solo e na água (nos quatro níveis de imersão analisados), não parece adequado para substituir integralmente a utilização deste método de treinamento em solo. Apesar disso, o treinamento de pliometria na água, por induzir reduções da FRS, apresenta excelentes possibilidades de utilização dependendo do objetivo do treinamento e do momento da temporada competitiva, sendo necessário considerar o nível de imersão, a condição musculoesquelética e as características antropométricas dos indivíduos.