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1.
J Sports Sci ; 38(20): 2314-2320, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32965184

RESUMO

This study was designated to investigate the kinematical differences between successful and faulty spikes, in order to identify the best strategies leading to better spike performance. Simulating a real-game condition, 13 elite youth attackers performed 6 spikes in the presence of 2 blocks. The kinematic variables of the spike performances were recorded using 6 optoelectronic cameras (Vicon Motion systems, Oxford, UK). The paired sample t-test was used to compare the kinematic variables recorded during the delivery of successful and faulty spikes. Among the successful trials, both the angular velocities of the knees (≈12.4%) and hips (≈13.3%), and the vertical velocity of the centre of mass at take-off (≈6.5%) and arm swing (≈8.2%) were considerably higher during the plant phase. Consequently, the jump (≈4.3%) and spike (≈1.5%) heights, as well as the wrist velocity (≈5.5%), were significantly higher during the jump phase of successful spikes. In successful spike performances, the attackers adopted higher hip and knee angular velocities, combined with efficient arm swings, to produce higher take-off velocities and reach higher jump heights. This approach provides them with the better position regarding the ball and the blockers to find the best path and hit the ball with higher arm velocities.


Assuntos
Destreza Motora/fisiologia , Voleibol/fisiologia , Adolescente , Braço/fisiologia , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Cotovelo/fisiologia , Quadril/fisiologia , Humanos , Joelho/fisiologia , Ombro/fisiologia , Estudos de Tempo e Movimento , Punho/fisiologia
2.
PLoS One ; 15(8): e0227394, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866148

RESUMO

The aim of this study was to assess the impact of a 6-week specialized training program aimed at strengthening core muscles to improve the effectiveness of selected elements of a swimming race on a group of Polish swimmers. Sixteen male national level swimmers (21.6 ± 2.2 years) participated in the research. The competitors were randomly assigned to 1 of 2 groups before the data collection process: an experimental (EG, n = 8) and a control (CG, n = 8) group. Both groups of swimmers underwent the same training program in the water environment (volume and intensity), while swimmers from the EG additionally performed specific core muscle training. The task of the swimmers was an individual front crawl swim of 50 m, during which the kinematic parameters of the start jump, turn and swimming techniques were recorded using a video camera system. In both groups, a minor increase in the flight phase was observed at the start (EG = 0.06 m, 1.8%; p = 0.088; CG = 0.08 m, 2.7%; p = 0.013). The time to cover a distance of 5 m after the turn and the recorded average speed in swimming this distance for the EG statistically significantly improved by 0.1 s (-28.6%; p < 0.001) and 3.56 m∙s-1 (23.2%; p = 0.001), respectively. In the EG, a statistically significant improvement in 50 m front crawl swimming performance of 0.3 s (-1.2%, p = 0.001) was observed. The results of the research show that the implementation of isolated strengthening of the stabilizing muscles seems to be a valuable addition to the standard training of swimmers.


Assuntos
Exercício Físico/fisiologia , Condicionamento Físico Humano/métodos , Natação/fisiologia , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Terapia por Exercício , Humanos , Masculino , Força Muscular/fisiologia , Músculos , Polônia , Treinamento de Resistência/métodos , Adulto Jovem
3.
PLoS One ; 15(8): e0237331, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32822398

RESUMO

Speed skating is a technical endurance sport. Still, little is known about technical changes in junior speed skaters. Therefore, changes in technique throughout a 1500-m time-trial of elite junior speed skaters is investigated to explore differences between sexes, performance levels and competitive seasons. At (inter)national 1500-m competitions, knee and push-off angles were obtained for 120 elite junior speed skaters (56 female, 64 male, age 17.6±1.1 years) per lap at 250m (lap 1), 650m (lap 2), 1050m (lap 3) and 1450m (lap 4). Additionally, 1500m end-times and lap-times were obtained to divide skaters in faster and slower performance groups and to analyze pacing behavior. Fifteen skaters (8 female, 7 male, age 17.3±1.5 years) were measured again after 1.6±0.6 years. (Repeated measures) ANOVAs were used for statistical analyses (p<0.05). ICC, determined in a pilot study, was 0.55 for knee and 0.76 for push-off angles. Elite junior speed skaters increased their knee angles throughout the race (p<0.005), regardless of sex (p = 0.110) or performance level (p = 0.714). Push-off angles increased from lap 1-3 (p<0.001), in which men showed a larger decay than female skaters (p<0.05), this holds for both performance groups (p = 0.103). Faster skaters had smaller knee and push-off angles than slower skaters (p<0.05). Males showed smaller body angles than females (p<0.001). Faster male and female skaters showed a relative slower start and faster lap 3 compared to slower skaters (p<0.05). Development over competitive seasons showed a shift towards smaller push-off angles (p = 0.038) and less decay in knee angles from lap 2-3 (p = 0.026). The present study shows that technique throughout the 1500m deteriorates. Deterioration in technique is regardless of performance level, even with different pacing behaviors. Differences between sexes were found for push-off angles. The longitudinal development suggests changes in technique towards senior level and highlights the importance of studying juniors separate from seniors.


Assuntos
Atletas/estatística & dados numéricos , Desempenho Atlético/fisiologia , Locomoção/fisiologia , Patinação/fisiologia , Adolescente , Fatores Etários , Desempenho Atlético/estatística & dados numéricos , Desempenho Atlético/tendências , Feminino , Humanos , Articulação do Joelho/fisiologia , Masculino , Países Baixos , Projetos Piloto , Fatores Sexuais , Patinação/estatística & dados numéricos , Patinação/tendências , Fatores de Tempo
4.
PLoS One ; 15(8): e0236959, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760122

RESUMO

The study aims were to describe positional differences in the acceleration and sprint profiles of professional football players in match-play, and analyse start speeds required based on the intensity of accelerations and decelerations. This longitudinal study was conducted over thirteen competitive microcycles in a professional football team from LaLiga 123. Data were collected through electronic performance tracking systems. Every player was categorised based on the playing position: central defender (CD), full-back (FB), forward (FW), midfielder (MF), and wide midfielder (WMF). In respect of acceleration profile, positional differences were found for all variables (p < 0.05), except average magnitude of accelerations (ACCAVG, p = 0.56) and decelerations (DECAVG, p = 0.76). The sprint profile also showed positional differences for all variables (p < 0.05), apart from sprint duration (p = 0.07). In addition, although low-intensity accelerations required significantly greater start speeds (Vo) than high-intensity accelerations in WMF (0.4 ± 0.2 km/h; p < 0.05) and FW (0.4 ± 0.2 km/h; p < 0.05), no significant differences (p > 0.05) were found in CD, FB, and MF. However, high-intensity decelerations were performed at significantly higher Vo than low-intensity decelerations in MF (2.65 ± 0.1 km/h; p < 0.05), FW (3.3 ± 0.1 km/h; p < 0.05), FB (3.9 ± 0.4 km/h; p < 0.05), WMF (4.3 ± 0.3 km/h; p < 0.05), and CD (4.1 ± 0.7 km/h; p < 0.05). Therefore, positional differences exist for most variables of the acceleration and sprint profiles. In addition, different Vo were observed between high-intensity and low-intensity accelerations as well as high-intensity and low-intensity decelerations.


Assuntos
Desempenho Atlético/fisiologia , Futebol/fisiologia , Aceleração , Adulto , Desaceleração , Humanos , Estudos Longitudinais , Masculino , Monitorização Ambulatorial , Corrida/fisiologia , Espanha , Dispositivos Eletrônicos Vestíveis , Adulto Jovem
5.
PLoS One ; 15(8): e0237768, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32813742

RESUMO

INTRODUCTION: In cycling, the utilization of the drops position (i.e. the lowest handlebar position relative to the ground) allows for reduced frontal area, likely improved aerodynamics and thus performance compared to the tops (i.e. the position producing the most upright trunk). The reduced trunk angle during seated submaximal cycling has been shown to influence cardiorespiratory factors but the effects on pedalling forces and joint specific power are unclear. The purpose of this study was to investigate the effect of changing handgrip position on joint specific power and cycling kinematics at different external work rates in recreational and professional cyclists. METHOD: Nine professional and nine recreational cyclists performed cycling bouts using three different handgrip positions and three external work rates (i.e. 100W, 200W and external work rate corresponding to the lactate threshold (WRlt)). Joint specific power was calculated from kinematic measurements and pedal forces using 2D inverse dynamics. RESULTS: We found increased hip joint power, decreased knee joint power and increased peak crank torque for the professional cyclist compared to the recreational cyclists, but only at WRlt where the professional cyclists were working at a higher external work rate. There was no main effect of changing handgrip position on any joint, but there was a small interaction effect of external work rate and handgrip position on hip joint power contribution (Generalized eta squared (ηg2) = 0.012). At 100W, changing handgrip position from the tops to the drops decreased the hip joint contribution (-2.0 ± 3.9 percentage points (pct)) and at the WRlt, changing handgrip position increased the hip joint power (1.6 ± 3.1 pct). There was a small effect of handgrip position with the drops leading to increased peak crank torque (ηg2 = 0.02), increased mean dorsiflexion (ηg2 = 0.05) and increased hip flexion (ηg2 = 0.31) compared to the tops. DISCUSSION: The present study demonstrates that there is no main effect of changing handgrip position on joint power. Although there seems to be a small effect on hip joint power when comparing across large ranges in external work rate, any potential negative performance effect would be outweighed by the aerodynamic benefit of the drops position.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Postura/fisiologia , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Mãos/fisiologia , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Torque , Adulto Jovem
6.
Cuad. psicol. deporte ; 20(3): 95-108, jul. 2020. tab
Artigo em Espanhol | IBECS | ID: ibc-193544

RESUMO

El objetivo fue determinar si la técnica de tiro libre ejecutada por jugadores de baloncesto de entre 9 y 11 años no participantes en ninguna selección autonómica y nacional coincidió con la técnica reportada por la literatura y estudios previos. El trabajo se realizó diferenciando la técnica de tiro antes de la salida y a la salida del balón. Participaron 12 jugadores varones de entre 9 y 11 años (M = 10,43, DT = ,63) que nunca habían participado en ninguna selección autonómica ni nacional. Se utilizó la metodología observacional a través de un diseño puntual/nomotético/multidimensional. Se grabó a los jugadores realizando un test que constaba de 10 tiros libres. Posteriormente, dos observadores observaron la ejecución técnica de cada uno de los tiros realizados por los jugadores. Se realizó la detección de t-patterns mediante el software Theme V.6 EDU. No se detectó ningún t-pattern antes de la salida del balón ni a la salida debido a que los tiros se realizaron siguiendo conductas muy dispares, que no se repitieron de forma regular en el tiempo. En el presente trabajo se utilizó un instrumento de observación que permitió la obtención de información directamente aplicable a la realidad diferenciando lo que ocurre antes de la salida del balón y a la salida del mismo. Se comprobó que los jugadores analizados, los cuales no jugaban en ninguna selección, ejecutaron una técnica de tiro que contrastaba en varios criterios con las recomendaciones propuestas por la literatura y estudios previos


The purpose was to determine whether the free throw technique of under-12 basketball players, who did not participated in any regional and national team, was similar to the technique reported by the literature and previous studies. The analysis differentiated prior to shoot and at ball release moments. Participant were 12 male players between 9 and 11 years old (M = 10.43, SD =, 63) who had never participated in any regional and national team. The observational methodology was used through a point/nomothetic/multidimensional design. The players were recorded performing a test consisting of 10 free throws. Two observers observed the technical execution of each of the shots made by the players. T-patterns were detected using Theme V.6 EDU software. Neither prior to ball release nor at ball release t-patterns were detected because the free throws followed very different behaviours, which were not repeated regularly over time. In the present work, an observation instrument was used that allowed obtaining information directly applicable to reality, differentiating between the free throw technique prior to shoot and at ball release moments. The analysed players, who did not play in any regional and national team, executed a free throw technique that contrasted in several criteria with the literature and previous studies recommendations


O objetivo foi determinar se a técnica do tiro livre executada por jogadores de basquete entre 9 e 11 anos de idade que não participavam de nenhuma seleção regional e nacional coincidia com a técnica relatada na literatura e em estudos anteriores. O trabalho foi realizado diferenciando a técnica do chute antes do início e do início da bola. Participaram 12 jogadores do sexo masculino entre 9 e 11 anos (M = 10,43, DT =, 63) que nunca haviam participado de nenhuma equipe regional ou nacional. A metodologia observacional foi utilizada através de um desenho pontual/nomotético/multidimensional. Os jogadores foram gravados realizando um teste composto por 10 chutes da linha de lance livre. Posteriormente, dois observadores observaram a execução técnica de cada um dos tiros feitos pelos jogadores. Os t-patterns foram detectados usando o software Theme V.6 EDU. Nenhum t-patterns foi detectado antes do início da bola ou no início, porque os chutes foram feitos seguindo comportamentos muito diferentes, que não foram repetidos regularmente ao longo do tempo. No presente trabalho, foi utilizado um instrumento de observação que permitiu obter informações diretamente aplicáveis à realidade, diferenciando o que ocorre antes da saída da bola e da saída da bola. Verificou-se que os jogadores analisados, que não jogaram em nenhuma seleção, executaram uma técnica de chute que contrasta em vários critérios com as recomendações propostas pela literatura e estudos anteriores


Assuntos
Humanos , Masculino , Criança , Basquetebol/estatística & dados numéricos , Desempenho Atlético/estatística & dados numéricos , Desempenho Atlético/fisiologia , Esportes Juvenis/estatística & dados numéricos
8.
PLoS One ; 15(7): e0236102, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32667941

RESUMO

Cross-country skiers use different sub-techniques like 'gears' (diagonals stride, double poling with kick, and double poling) depending on terrain (incline) and demand (speed and external work rate). Previous studies have identified the major effect of speed and incline, but not any potential interaction between these parameters: the incline-speed combination determines the work rate, which in itself may be a controlling factor. The aim of this study was to investigate the role of these task conditions (external work rate, speed, incline) and their interactions on the choice of sub-technique in classical roller skiing. Twelve male and nine female cross-country skiers executed three subsets of protocols in which two of three condition parameters were altered every 15 seconds while roller skiing on a treadmill. This design created a quasi-random set of combinations of speed, incline and work rate that were analysed on sub-technique choice. A repeated measures model with sex as between subject factor was conducted for each subset of protocols. The incline appeared to be the factor affecting sub-technique choice most, but not exclusively; at constant incline, athletes applied different sub-techniques, depending mostly on speed rather than work rate. Most athletes did not use one particular sub-technique for a given speed-incline-work rate combination, but it depended on the protocol and direction of condition change in the constant speed protocol (hysteresis). Only minor differences between men and women existed regarding the impact of condition factor on sub-technique choice. The findings disagree with the notion of a simple mechanism that explains the choice of sub-technique, but rather opt for a complex structure that entangles various mechanisms which play a role in the choice of sub-technique under moderate effort conditions.


Assuntos
Atletas/psicologia , Desempenho Atlético/fisiologia , Comportamento de Escolha , Exercício Físico , Esqui/fisiologia , Análise e Desempenho de Tarefas , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Consumo de Oxigênio
9.
PLoS One ; 15(7): e0236024, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32687507

RESUMO

Training prescription and monitoring of team-sport athletes rely on accurate quantification of player movement. Our aim was to determine the sensitivity, reliability and construct validity of measures derived from a wearable device incorporating Global Positioning System (GPS) and accelerometer technology to quantify the peak periods of rugby competition. Match movement data were collected from 30 elite and 30 sub-elite rugby union players across respective competitive seasons. Accelerometer and GPS measures were analysed using a rolling average to identify peak movement for epochs ranging from 5 to 600 seconds. General linear mixed modelling was used to quantify the effects of playing position and match-half on the peak movement and variabilities within and between players represented reliability of each measure. Mean positional differences and match-half changes were assessed via standardisation and magnitude-based decisions. Sensitivity of measures was quantified via evaluation of ("signal") and typical error of measurement ("noise"). GPS and accelerometer measures had poor sensitivity for quantifying peak movement across all epochs and both levels of rugby union competition (noise 4× to 5× the signal). All measures displayed correspondingly low reliability across most epochs and both levels of competition (ICC<0.50). Construct validity was evident in mean differences between playing positions and match halves that were consistent with expected activity profiles in rugby union. However, it was clear from the pattern of differences across epoch durations and levels of competition that GPS and accelerometer measures provided different information about player movement. The poor sensitivity and low reliability of GPS and accelerometer measures of peak movement imply that rugby union players need to be monitored across many matches to obtain adequate precision for assessing individuals. Although all measures displayed construct validity, accelerometers provided meaningful information additional to that of GPS. We recommend using accelerometers alongside GPS to monitor and prescribe match respresentative training.


Assuntos
Acelerometria/métodos , Atletas/estatística & dados numéricos , Desempenho Atlético/fisiologia , Futebol Americano/fisiologia , Sistemas de Informação Geográfica/instrumentação , Corrida/fisiologia , Análise e Desempenho de Tarefas , Adulto , Humanos , Masculino , Curva ROC , Reprodutibilidade dos Testes
10.
J Sports Sci ; 38(16): 1897-1912, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32602418

RESUMO

To date, little is known about overreaching (OR) and the overtraining syndrome (OTS) in strength sports and resistance training (RT) populations. However, the available literature may elucidate the occurrence of both conditions in these populations. A scoping review was conducted. SPORTDiscus, Scopus and Web of Science were searched in a robust and systematic manner, with relevant articles analysed. 1170 records were retrieved during an initial search, with a total of 47 included in the review. Two broad themes were identified during data extraction: 1) overreaching in strength sports; 2) overreaching and overtraining syndrome in RT. Short-term periods of OR achieved with either high-volume or high-intensity RT can elicit functional OR (FOR) but there is also evidence that chronic high-volume and/or intensity RT can lead to non-functional overreaching (NFOR). There is minimal evidence to suggest that true OTS has occurred in strength sports or RT based on the studies entered during this review. More research is needed to develop robust guiding principles for practitioners. Additionally, due to the heterogeneous nature of the existing literature, future research would benefit from the development of practical tools to identify and diagnose the transition from FOR to NFOR, and subsequently OTS in strength athletes and RT populations. ABBREVIATIONS: RT: Resistance training; OR: Overreaching; FOR: Functional overreaching; NFOR: Non-functional overreaching; OTS: Overtraining syndrome; WP: Weightlifting performance.


Assuntos
Traumatismos em Atletas/etiologia , Transtornos Traumáticos Cumulativos/etiologia , Fadiga/etiologia , Treinamento de Resistência/efeitos adversos , Desempenho Atlético/fisiologia , Biomarcadores/sangue , Índice de Massa Corporal , Doença Crônica , Suplementos Nutricionais , Humanos , Músculo Esquelético/anatomia & histologia
11.
J Sports Sci ; 38(11-12): 1432-1440, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32627682

RESUMO

We study the developmental and professional activities engaged in by 86 female adult soccer players from the senior national teams of Australia, Canada, England, Sweden, and the United States of America. Players completed the Participation History Questionnaire (PHQ) to elicit the amount and type of activities engaged in across their developmental and professional years, including milestones, soccer-specific activity and engagement in other sport activity. Greater specialisation than diversification characterised their childhood developmental activities, including all players starting in soccer in childhood and accumulating more hours in soccer activity than other sports during this period. However, interindividual variation further characterised these childhood activities, with a proportion of players diversifying into other sports and/or soccer play to a greater or lesser degree during childhood when compared to the other players. The amount of coach-led soccer practice increased for all players across their development culminating in an average of 15-16 h/wk across a 40-week season in early adulthood. In contrast, the amount of engagement in other sports and soccer peer-led play varied between players but generally decreased across adolescence to negligible amounts in late adolescence. Findings are commensurate with the deliberate practice framework and early engagement.


Assuntos
Aptidão , Desempenho Atlético/fisiologia , Comportamento Competitivo/fisiologia , Destreza Motora/fisiologia , Futebol/fisiologia , Adulto , Austrália , Canadá , Inglaterra , Feminino , Humanos , Condicionamento Físico Humano , Especialização , Suécia , Estados Unidos
12.
J Sports Sci ; 38(20): 2359-2366, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32627681

RESUMO

Successful sprinting depends on covering a specific distance in the shortest time possible. Although external forces are key to sprinting, less consideration is given to the duration of force application, which influences the impulse generated. This study explored relationships between sprint performance measures and external kinetic and kinematic performance indicators. Data were collected from the initial acceleration, transition and maximal velocity phases of a sprint. Relationships were analysed between sprint performance measures and kinetic and kinematic variables. A commonality regression analysis was used to explore how independent variables contributed to multiple-regression models for the sprint phases. Propulsive forces play a key role in sprint performance during the initial acceleration (r = 0.95 ± 0.03) and transition phases (r = 0.74 ± 0.19), while braking duration plays an important role during the transition phase (r = -0.72 ± 0.20). Contact time, vertical force and peak propulsive forces represented key determinants (r = -0.64 ± 0.31, r = 0.57 ± 0.35 and r = 0.66 ± 0.30, respectively) of maximal velocity phase performance, with peak propulsive force providing the largest unique contribution to the regression model for step velocity. These results clarified the role of force and time variables on sprinting performance.


Assuntos
Desempenho Atlético/fisiologia , Corrida/fisiologia , Aceleração , Fenômenos Biomecânicos , Feminino , Humanos , Cinética , Masculino , Análise de Regressão , Estudos de Tempo e Movimento
13.
Apunts, Med. esport (Internet) ; 55(206): 53-61, abr.-jun. 2020. graf, tab
Artigo em Inglês | IBECS | ID: ibc-191744

RESUMO

This study examines the effects of two strength training (ST) programs, one based on mean propulsive velocity (MPV) and another under the traditional method, the % one-repetition maximum (1RM), on neuromuscular performance and muscle composition in girls who play soccer. Fifty players with an average age of 13.6 ± 1.2 years participated in the study and were randomly assigned into three groups: a maximal execution velocity training group (VG, n = 15), a maximal strength group (RMG, n = 13), and a control group (CG, n = 18). The study was developed for a period of twelve weeks during regular team training to prepare for the season. The VG and RMG groups performed additional strength or muscle power training three times a week, including movements of full squat and pedaling on a cycle ergometer. The two types of training groups and the control group exhibited significant gains. However, the greatest increases were achieved with VG training, with significant increases (p < 0.000) in maximal strength, (p < 0.000) squat power, (p < 0.000) velocity over 30 m, (p < 0.000) cycle ergometer power, and (p < 0.008) lower limb muscle mass. Statistically significant differences were observed between VG and RMG in countermovement jump (CMJ) (p < 0.008) and squat power (p < 0.01) tests, between VG and CG in CMJ (p < 0.01), squat power (p < 0.000), and maximal squat strength (p < 0.000), and between RMG and CG in maximal squat strength (p < 0.000) only. These findings might indicate that high-velocity ST can be performed simultaneously with regular training to improve the explosive actions of soccer players


No disponible


Assuntos
Humanos , Feminino , Criança , Adolescente , Desempenho Atlético/fisiologia , Futebol/fisiologia , Força Muscular/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Junção Neuromuscular/fisiologia , Análise de Variância , Treinamento de Resistência/métodos
14.
J Sports Med Phys Fitness ; 60(7): 979-984, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32597615

RESUMO

BACKGROUND: Plyometric exercises are often used to develop lower limb strength and performance-related biomechanics such as leg stiffness. However, the effectiveness of plyometric training may depend on participants' own training and performance demands. The purpose of this study was to examine the effect of plyometric training on Reactive Strength Index (RSI) and leg stiffness (Kleg) on young athletes of different sports. METHODS: Forty eight female athletes (25 Taekwondo (TKD) and 23 rhythmic gymnastics (RG), mean±SD: age: 8.94±2.50 years; mass: 29.73±7.69 kg; height: 138.84±11.90 cm; training experience: 4.62±2.37 years) participated in this study. Participants were randomly assigned to experimental (PT, N.=24) and control (CG, N.=24) groups. The PT group followed a twice-weekly plyometric training program for 4 weeks. Plyometric drills lasted approximately 5-10 s, and at least 90 s rest was allowed after each set. To examine RSI, participants performed trials of five maximal CMJs. Submaximal hopping (20 hops) was performed in order to examine leg stiffness. RESULTS: Significant interaction effect was found for RSI and the post hoc analysis showed that RSI significantly increased by 35% (P=0.017) in RG athletes, whereas a significantly reduction by 28% (P=0.004) was revealed in TKD athletes. The interaction effect between time and group was statistically significant for Kleg (P<0.05) with Kleg significantly increasing by 31% (P=0.008) in TKD athletes, but remaining unchanged (P>0.05) in RG athletes. CONCLUSIONS: The results showed that the effect of a 4-week plyometric training program on RSI and leg stiffness is sport dependent. Further, the applied plyometric program was effective in reducing ground contact time and therefore increasing leg stiffness.


Assuntos
Ginástica/fisiologia , Extremidade Inferior/fisiologia , Artes Marciais/fisiologia , Força Muscular/fisiologia , Exercício Pliométrico/métodos , Adolescente , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Criança , Feminino , Humanos , Movimento/fisiologia
15.
J Sports Med Phys Fitness ; 60(7): 1034-1039, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32597619

RESUMO

BACKGROUND: Creatine represents a natural supplement and ergogenic aid for sport performance, but there are several concerns regarding its safety for health. The present double-blind placebo-controlled study evaluated the effect of creatine monohydrate supplementation on a panel of blood and urine health indicators in resistance training practitioners. METHODS: Eighteen males performing resistance training three times per week were supplemented with 0.3 g/kg per day creatine monohydrate for 7 days and compared with matched controls supplemented with dextrosol. Blood and urine samples were collected pre- and 30 days post-supplementation to evaluate 41 biochemical parameters and renal function. RESULTS: Creatine monohydrate supplementation did not cause adverse events and, as expected, promoted an increase of the performance and body weight. No modification of red blood cells parameters, white blood cells profile, blood lipid profile, metabolic and urine markers, hepatic and renal function were observed in the supplemented group. CONCLUSIONS: Despite the expected weight increase, the creatine monohydrate supplementation is safe for health and no detrimental effects on different organs and physiological systems were observed in our cohort of volunteers.


Assuntos
Desempenho Atlético/fisiologia , Creatina/administração & dosagem , Creatina/efeitos adversos , Suplementos Nutricionais , Substâncias para Melhoria do Desempenho/administração & dosagem , Substâncias para Melhoria do Desempenho/efeitos adversos , Treinamento de Resistência , Adulto , Biomarcadores/sangue , Biomarcadores/urina , Método Duplo-Cego , Testes Hematológicos , Humanos , Rim/fisiologia , Contagem de Leucócitos , Lipídeos/sangue , Fígado/fisiologia , Masculino , Músculo Esquelético/metabolismo , Ganho de Peso , Adulto Jovem
16.
PLoS One ; 15(6): e0234458, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32569264

RESUMO

We investigated the association of multiple single nucleotide polymorphisms (SNPs) with athlete status and power/speed performance in elite male youth soccer players (ESP) and control participants (CON) at different stages of maturity. ESP (n = 535; aged 8-23 years) and CON (n = 151; aged 9-26 years) were genotyped for 10 SNPs and grouped according to years from predicted peak-height-velocity (PHV), i.e. pre- or post-PHV, to determine maturity status. Participants performed bilateral vertical countermovement jumps, bilateral horizontal-forward countermovement jumps, 20m sprints and modified 505-agility tests. Compared to CON, pre-PHV ESP demonstrated a higher ACTN3 (rs1815739) XX ('endurance') genotype frequency distribution, while post-PHV ESP revealed a higher frequency distribution of the PPARA (rs4253778) C-allele, AGT (rs699) GG genotype and NOS3 (rs2070744) T-allele ('power' genotypes/alleles). BDNF (rs6265) CC, COL5A1 (rs12722) CC and NOS3 TT homozygotes sprinted quicker than A-allele carriers, CT heterozygotes and CC homozygotes, respectively. COL2A1 (rs2070739) CC and AMPD1 (rs17602729) GG homozygotes sprinted faster than their respective minor allele carrier counterparts in CON and pre-PHV ESP, respectively. BDNF CC homozygotes jumped further than T-allele carriers, while ESP COL5A1 CC homozygotes jumped higher than TT homozygotes. To conclude, we have shown for the first time that pre- and post-PHV ESP have distinct genetic profiles, with pre-PHV ESP more suited for endurance, and post-PHV ESP for power and speed (the latter phenotypes being crucial attributes for post-PHV ESP). We have also demonstrated that power, acceleration and sprint performance were associated with five SNPs, both individually and in combination, possibly by influencing muscle size and neuromuscular activation.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Perfil Genético , Maturidade Sexual/fisiologia , Futebol , Aceleração , Actinina/genética , Adolescente , Estudos de Casos e Controles , Criança , Colágeno Tipo II/genética , Colágeno Tipo V/genética , Frequência do Gene , Humanos , Masculino , Força Muscular/genética , Polimorfismo de Nucleotídeo Único , Corrida/fisiologia , Adulto Jovem
17.
PLoS One ; 15(6): e0234401, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32584826

RESUMO

Previous studies suggest that marathon running induces lower extremity muscle damage. This study aimed to examine inter- and intramuscular differences in hamstring muscle damage after a marathon using transverse relaxation time (T2)-weighted magnetic resonance images (MRI). 20 healthy collegiate marathon runners (15 males) were recruited for this study. T2-MRI was performed before (PRE) and at 1 (D1), 3 (D3), and 8 days (D8) after marathon, and the T2 values of each hamstring muscle at the distal, middle, and proximal sites were calculated. Results indicated that no significant intermuscular differences in T2 changes were observed and that, regardless of muscle, the T2 values of the distal and middle sites increased significantly at D1 and D3 and recovered at D8, although those values of the proximal site remained constant. T2 significantly increased at distal and middle sites of the biceps femoris long head on D1 (p = 0.030 and p = 0.004, respectively) and D3 (p = 0.007 and p = 0.041, respectively), distal biceps femoris short head on D1 (p = 0.036), distal semitendinosus on D1 (p = 0.047) and D3 (p = 0.010), middle semitendinosus on D1 (p = 0.005), and distal and middle sites of the semimembranosus on D1 (p = 0.008 and p = 0.040, respectively) and D3 (p = 0.002 and p = 0.018, respectively). These results suggest that the distal and middle sites of the hamstring muscles are more susceptible to damage induced by running a full marathon. Conditioning that focuses on the distal and middle sites of the hamstring muscles may be more useful in improving recovery strategies after prolonged running.


Assuntos
Traumatismos em Atletas/diagnóstico por imagem , Traumatismos em Atletas/etiologia , Músculos Isquiossurais/diagnóstico por imagem , Músculos Isquiossurais/lesões , Corrida/fisiologia , Traumatismos em Atletas/fisiopatologia , Desempenho Atlético/fisiologia , Feminino , Músculos Isquiossurais/patologia , Humanos , Contração Isométrica/fisiologia , Japão , Imagem por Ressonância Magnética , Masculino , Fatores de Tempo , Torque , Adulto Jovem
18.
PLoS One ; 15(6): e0233796, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32497130

RESUMO

BACKGROUND: Rugby union match demands are complex, requiring the development of multiple physical qualities concurrently. Quantifying the physical qualities of age grade rugby union players is vital for practitioners to support athlete preparation and long-term development. AIM: This systematic review aimed to identify the methods used to quantify the physical qualities of male age grade (≤ Under-20) rugby union players, present the normative values for physical qualities, and compare physical qualities between age grades and positions. METHODS: Electronic databases were systematically reviewed from the earliest record to November 2019 using key words relating to sex, age, sport and physical testing. RESULTS: Forty-two studies evaluated the physical qualities of age grade rugby union players. Seventy-five tests were used to quantify body composition, muscular strength, muscular power, linear speed, change of direction ability, aerobic capacity and anaerobic endurance. Thirty-one studies met the eligibility criteria to present the physical qualities. Physical qualities differentiate between age groups below Under-16, while differences in older age groups (Under-16 to Under-20) are not clear. Positional differences are present with forwards possessing greater height, body mass, body fat percentage and strength while backs are faster and have greater aerobic capacities. CONCLUSIONS: A wide variety of tests are used to assess physical qualities limiting between study comparisons. Although differences in older age grades are unclear, older age groups (Under-19-20) generally performed better in physical tests. Positional differences are associated with match demands where forwards are exposed to less running but a greater number of collisions. Practitioners can use the results from this review to evaluate the physical qualities of age grade rugby union players to enhance training prescription, goal setting and player development. Future research should consider the use of national standardised testing batteries due to the inconsistency in testing methods and small samples limiting the reporting of positional differences.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Teste de Esforço/métodos , Futebol Americano/fisiologia , Força Muscular/fisiologia , Adolescente , Composição Corporal/fisiologia , Tamanho Corporal/fisiologia , Criança , Humanos , Masculino , Resistência Física/fisiologia , Aptidão Física/fisiologia , Corrida/fisiologia , Adulto Jovem
19.
Int. j. morphol ; 38(3): 545-551, June 2020. tab, graf
Artigo em Inglês | LILACS | ID: biblio-1098285

RESUMO

SUMMARY: The objective of this research is to relate the performance in three vertical jump events with morphological variables of the foot and stature. A total of 177 practitioners of 12 sporting events aged 24.5 ±8.0 years, with 71.01 ±13.00 kg of body mass, 1.71±0.09 m height, and BMI of 24.29±3.24 kg·m-2 were evaluated with an anthropometer in terms of foot length (FL), forefoot width (FW), navicular height (NH), and hindfoot width (HW). These variables were normalized to the height of the subjects. From the footprint record the arch index (AI) was obtained, which indicates the morphology of the medial longitudinal foot arch (MLFA). Performance was evaluated in three vertical jump events: countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ), recording the height reached. FL, FW and HW show a weak positive correlation (r<0.4; p<0.05) with the heights achieved in the three types of jump. The stature is strongly associated with FL, FW and HW (r=0.8; r=0.7 and r=0.6; respectively; p<0.05) and with the height in CMJ, SJ, and DJ (r=0.37; r=0.41 and r=0.32, respectively, p<0.05). The only normalized morphological foot variable that maintained consistency in the correlations analysis was the normalized foot length (NFL) with CMJ (r = 0.2, p<0,05). The subjects whose left foot length was equivalent to 14 % of the stature jumped 27.94 ±6.63 cm, those with 15 % jumped 30.96 ±7.4 cm, and those with 16 % jumped 31.03 ±7.8 cm. FL, FW, HW, and stature are moderately correlated with performance in vertical jump events. However, after discarding the stature of the subjects, only the foot length maintained its relation with performance in CMJ.


RESUMEN: El objetivo de esta investigación fue relacionar el rendimiento en salto vertical con variables morfológicas del pie y estatura. 177 practicantes de 12 disciplinas deportivas de 24,5 ±8,0 años; 71,01 ±13,00 kg; 1,71 ±0,09 m, e IMC de 24,29 ±3,24 kg•m-2 fueron evaluados con un antropómetro obteniendo longitud de pie (FL), ancho de antepié (FW), altura navicular (NH) y ancho de retropié (HW). Estas variables fueron normalizadas a la estatura. Se midió la huella plantar obteniendo el índice del arco (AI), el cual indica la morfología del arco plantar longitudinal medial (MLFA). El rendimiento fue evaluado en tres pruebas de salto: salto con contramovimiento (CMJ), sentadilla con salto (SJ) y salto desde caída (DJ), registrando la altura alcanzada. FL, FW y HW mostraron una débil correlación positiva (r<0,4; p<0,05) con la altura alcanzada en los tres saltos. La estatura se asocia con FL, FW y HW (r=0,8; r=0,7 y r=0,6; respectivamente; p<0,05) y con la altura en CMJ, SJ y DJ (r=0,37; r=0,41 y r=0,32, respectivamente, p<0,05). La única variable normalizada del pie que mantuvo consistencia en el análisis de correlaciones fue la longitud del pie normalizada (NFL) con CMJ (r=0,2; p<0,05). Los sujetos cuyo pie tiene una longitud equivalente al 14 % de la estatura saltaron 27,94 ±6,63 cm, los que equivalen al 15 % saltaron 30,96 ±7,4 cm y quienes tuvieron un pie equivalente a un 16 % de la estatura saltaron 31,03 ±7,8 cm. FL, FW, HW y la estatura se correlacionan moderadamente con el rendimiento en salto vertical. Sin embargo, después de descartar la estatura de los sujetos, solamente la longitud del pie mantiene su relación con el rendimiento en CMJ.


Assuntos
Humanos , Masculino , Feminino , Adolescente , Adulto , Adulto Jovem , Desempenho Atlético/fisiologia , Pé/anatomia & histologia , Movimento
20.
Int J Sports Physiol Perform ; 15(6): 767-776, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32502972

RESUMO

CONTEXT: Combat sports are composed of high-intensity actions (eg, attacks, defensive actions, and counterattacks in both grappling and striking situations depending on the specific sport) interspersed with low-intensity actions (eg, displacement without contact, stepping) or pauses (eg, referee stoppages), characterizing an intermittent activity. Therefore, high-intensity interval training (HIIT) is at the essence of combat-sport-specific training and is used as complementary training, as well. HIIT prescription can be improved by using intensity parameters derived from combat-sport-specific tests. Specifically, the assessment of physiological indexes (intensity associated with the maximal blood lactate steady state, maximal oxygen consumption, and maximal sprint) or of time-motion variables (high-intensity actions, low-intensity actions, and effort:pause ratio) is a key element for a better HIIT prescription because these parameters provide an individualization of the training loads imposed on these athletes. PURPOSE: To present a proposal for HIIT prescription for combat-sport athletes, exemplifying with different HIIT protocols (HIIT short intervals, HIIT long intervals, repeated-sprint training, and sprint interval training) using combat-sport-specific actions and the parameters for the individualization of these protocols. CONCLUSIONS: The use of combat-sport-specific tests is likely to improve HIIT prescription, allowing coaches and strength and conditioning professionals to elaborate HIIT short intervals, HIIT long intervals, repeated-sprint training, and sprint interval training protocols using combat-sport actions, providing more specificity and individualization for the training sessions.


Assuntos
Desempenho Atlético/fisiologia , Comportamento Competitivo/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Tomada de Decisões , Humanos , Ácido Láctico/sangue , Consumo de Oxigênio/fisiologia
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