Vertical Jump Kinetic Parameters on Sand and Rigid Surfaces in Young Female Volleyball Players with a Combined Background in Indoor and Beach Volleyball.

Little is known about the differences in vertical jump biomechanics executed on rigid (RJS) and sand (SJS) surfaces in female indoor and beach volleyball players. Eleven young female beach volleyball players with a combined indoor and beach volleyball sport background performed squat jumps, countermovement jumps with and without an arm swing, and drop jumps from 40 cm on a RJS (force plate) and SJS (sand pit attached to the force plate). The results of the 2 (surface) × 4 (vertical jump test) repeated-measure ANOVA revealed a significant (p < 0.05) main effect of the surface and the vertical jump test on the jump height and time to achieve peak vertical body center of mass velocity. A significant (p < 0.05) main effect of the test, but not of the surface (p > 0.05), was observed for the other examined biomechanical parameters. The only significant (p < 0.05) jump height gain difference between RJS and SJS was observed for the utilization of the stretch-shortening cycle, which was higher in SJS (15.4%) compared to RJS (7.5%). In conclusion, as the testing was conducted during the beach volleyball competitive season, the examined female players showed adaptations relating the effective utilization of the pre-stretch and enhanced stability during the execution of the vertical jump tests on a SJS compared to RJS.

Evaluation of a beach volleyball skill instrument for the line shot attack / Avaliação de um instrumento de habilidade de voleibol de praia para o ataque de tiro à linha

ABSTRACT This study aimed to develop a test for measuring athletes' performance. Logical, content, construct, criterion validity, as well as reliability, were examined. Three beach volleyball experts evaluated how well the test evaluates the shot skill accuracy according to their judgment (logical validity). A group of eight beach volleyball experts analyzed the test and rated it on a scale of 1 to 7 regarding the relevance of the content as a measure of beach volleyball athlete's accuracy, the average score was calculated at 6.75 (SD=0.46) (content validity). 60 beach volleyball players divided into three equal groups of novices, intermediates, and experts were asked to undergo the test on two separate days. A one-way ANOVA between the three groups was performed, which indicated that the mean scores of the three groups differed significantly (p<0.001 for both days): experts achieved better scores than intermediates who in turn scored better than novices (construct validity). The athletes' scores were correlated with their proficiency level, using the Pearson Correlation test, which indicated very high positive (Day-1: r=0.956, n=60, p<0.001; Day-2: r=0.953, n=60, p<0.001) (criterion validity). The intraclass correlation coefficient was calculated between Day-1 and Day-2 and was found equal to 0.980 for average measures (p<0.001) and 0.961 for single measures (p<0.001). In conclusion, the requirements for logical, content, construct, criterion validity, and reliability have been met. Therefore, the line shot attack test can be used as a valid and reliable measurement instrument for evaluating the performance of beach volleyball athletes.

RESUMO Este estudo teve como objetivo desenvolver um teste para mensurar o desempenho de atletas. No teste foram examinados os seguintes itens: lógica, conteúdo, construto, validade de critério, bem como confiabilidade. Três especialistas em voleibol de praia avaliaram o quão bem o teste avalia a precisão da habilidade de arremesso de acordo com seu julgamento (validade lógica). Um grupo de oito especialistas em vôlei de praia analisou o teste e o classificou em uma escala de 1 a 7 quanto à relevância do conteúdo como medida de precisão do atleta de vôlei de praia, a pontuação média foi calculada em 6,75 (DP=0,46) (validade de conteúdo). A amostra foi constituída por 60 jogadores de vôlei de praia divididos em três grupos: novatos, intermediários e experientes foram convidados a realizar o teste em dois dias separados. Uma ANOVA de uma via entre os três grupos foi realizada, o que indicou que as pontuações médias dos três grupos diferiram significativamente (p<0,001 para ambos os dias): os especialistas obtiveram melhores pontuações do que os intermediários que, por sua vez, pontuaram melhor do que os novatos (validade de construção). As pontuações dos atletas foram correlacionadas com seu nível de proficiência, usando o teste de correlação de Pearson, indicando correlação muito alta e positiva (Dia-1: r=0,956, n=60, p<0,001; Dia-2: r=0,953, n=60, p<0,001) (validade de critério). O coeficiente de correlação intraclasse foi calculado entre o Dia-1 e o Dia-2 e foi igual a 0,980 para medidas médias (p<0,001) e 0,961 para medidas isoladas (p<0,001). Em conclusão, os requisitos de lógica, conteúdo, construto, validade de critério e confiabilidade foram atendidos. Portanto, o teste de ataque de tiro de linha pode ser usado como um instrumento de medida válido e confiável para avaliar o desempenho de atletas de vôlei de praia.

Spike Arm Swing Techniques of Olympics Male and Female Elite Volleyball Players (1984-2021).

In the last decades, indoor volleyball has experienced significant rule changes and a high player specialization in both sexes. Different spike attack arm swing techniques have developed which might affect performance and risk of injury. While a variety of arm swing techniques was already shown in world class beach volleyball players, it is unclear if this is also true for world class indoor volleyball. Therefore, the purpose of this study was to assess the spike attack arm swing techniques of Olympic volleyball winners and finalists (1984-2021) and to investigate possible differences between sex, playing position, scoring system, and compared to beach volleyball. Eighty-two male (M) and 85 female (F) players were assessed from video recordings from ten competitions. Five different arm swing techniques in the cocking phase (Straight, Bow-and-arrow high, Bow-and-arrow low, Snap, Circular) were classified by two experts. The most frequent technique for both sexes was the Circular (M = 40.2%; F = 38.8%), followed by Snap (M = 28.0%; F = 23.5%), Bow-and-arrow low (M = 20.7%; F = 21.2%), Bow-and-arrow high (M = 7.3% F = 11.8%), and Straight (M = 3.7%; F = 4.7%). Bow-and-arrow high and Straight techniques were significantly less used than other techniques in both sexes. There were no significant differences (p > 0.05) in arm swing techniques between sexes, playing positions, and scoring system but significant differences (p < 0.001) to beach volleyball. Although most volleyball textbooks only describe the Bow-and-arrow techniques, most of the world class indoor volleyball players used Circular and Snap arm swing techniques. Reasons for that could be the implicit knowledge of players (and coaches) regarding increased performance (ball speed) and injury prevention. Based on these results we suggest to critically revise arm swing technique training especially for young players and players with shoulder problems.

Drop Jumping on Sand Is Characterized by Lower Power, Higher Rate of Force Development and Larger Knee Joint Range of Motion.

Plyometric training on sand is suggested to result in advanced performance in vertical jumping. However, limited information exists concerning the biomechanics of drop jumps (DJ) on sand. The purpose of the study was to compare the biomechanical parameters of DJs executed on rigid (RIGID) and sand (SAND) surface. Sixteen high level male beach-volleyball players executed DJ from 40 cm on RIGID and SAND. Force- and video-recordings were analyzed to extract the kinetic and kinematic parameters of the DJ. Results of paired-samples t-tests revealed that DJ on SAND had significantly (p < 0.05) lower jumping height, peak vertical ground reaction force, power, peak leg stiffness and peak ankle flexion angular velocity than RIGID. In addition, DJ on SAND was characterized by significantly (p < 0.05) larger rate of force development and knee joint flexion in the downward phase. No differences (p > 0.05) were observed for the temporal parameters. The compliance of SAND decreases the efficiency of the mechanisms involved in the optimization of DJ performance. Nevertheless, SAND comprises an exercise surface with less loading during the eccentric phase of the DJ, thus it can be considered as a surface that can offer injury prevention under demands for large energy expenditure.

Biomechanical differences of arm swing countermovement jumps on sand and rigid surface performed by elite beach volleyball players.

The purpose of this study was to investigate the possible arm swing effect on the biomechanical parameters of vertical counter movement jump due to differences of the compliance of the take-off surface. Fifteen elite male beach-volleyball players (26.2 ± 5.9 years; 1.87 ± 0.05 m; 83.4 ± 6.0 kg; mean ± standard deviation, respectively) performed counter movement jumps on sand and on a rigid surface with and without an arm swing. Results showed significant (p < .05) surface effects on the jump height, the ankle joint angle at the lowest height of the body center of mass and the ankle angular velocity. Also, significant arm swing effects were found on jump height, maximum power output, temporal parameters, range of motion and angular velocity of the hip. These findings could be attributed to the instability of the sand, which resulted in reduced peak power output due to the differences of body configuration at the lowest body position and lower limb joints' range of motion. The combined effect of the backward arm swing and the recoil of the sand that resulted in decreased resistance at ankle plantar flexion should be controlled at the preparation of selected jumping tasks in beach-volleyball.

Biomechanical differences in elite beach-volleyball players in vertical squat jump on rigid and sand surface.

The purpose of this investigation was to detect whether differences exist concerning the dynamic and kinematic parameters of vertical squat jump (SJ) on rigid (RS) and sand (SS) surface. Fifteen elite male beach volleyball players (age: 25.6 +/- 6.2 years; height: 188.0 +/- 3.5 cm; body mass: 83.2 +/- 6.0 kg; mean +/- SD, respectively) performed SJ. Force platform and kinematic analyses were used with paired sample T-tests to evaluate the differences. Vertical jump height was significantly smaller (p < .001) on SS than RS. Maximal force and maximal power were significantly higher on RS than SS (p < .05 and p < .01 respectively). Impulse time was larger in SS but with no significant difference (p = .286). Kinematic analysis revealed significant differences between the values of ankle joint during starting posture (p < .01) and of hip joint at the moment of take-off (p < .05). Ankle joint range of motion and angular velocity was larger in SS (p < .05). In conclusion, SJ height on SS was smaller than on RS because of the compliance and the instability of the sand. This resulted in a reduction in maximum force and take-off velocity. Furthermore, the compliance of SS made it hard for the ankle to push along the vertical axis of the movement of the body and as a result it slipped behind in an attempt to maximize propulsion. As a result, the body tries to balance and equalise this movement and move the hip to larger extension.