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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. [ABSTRACT FROM PUBLISHER]

The aim of this study was to investigate the relative influence of step length (SL) and step frequency (SF) on step velocity (SV) during the approach run of high-level long jumpers and to quantify the asymmetry of these step characteristics. Spatiotemporal data of the approach run were collected during national competition from 10 long jumpers (age 26.2 ± 4.1 years, height 1.84 ± 0.06 m, mass 72.77 ± 3.23 kg, personal best performance 7.96 ± 0.30 m). Analyses were conducted for total approach, early approach and late approach. For the total approach 4/10 athletes were SF reliant and 6/10 athletes favoured neither characteristic. At the early approach, 3/10 athletes were SF reliant and 7/10 athletes favoured neither. During late approach 2/10 athletes demonstrated SL reliance, 7/10 athletes were SF reliant and 1/10 athletes favoured neither. Four athletes displayed significant asymmetry for SL and three for SF. However, no athletes demonstrated significant asymmetry for SV indicating that the asymmetrical demands of take-off do not have a marked influence on step characteristic asymmetry, probably due to the constraints of the event. Consideration should be given to the potentially conflicting demands between limbs for individual athletes. [ABSTRACT FROM PUBLISHER]

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The purpose of the study was to investigate the occurrence of stride regulation at the approach phase of the long jump in athletes with normal vision and visually deprived Class F12 and F13 athletes. All the athletes exhibited the presence of a regulatory mechanism. In the normal vision group this occurred on the fifth-to-last stride. In Class F12 athletes regulation commenced on the fourth-to-last stride for males and third-to-last stride for females. Class F13 males commenced regulation, like the control group, on the fifth-to-last stride; but females commenced on the fourth-to-last stride. The study demonstrated that reduced vision does not prevent Class F12 and F13 athletes from applying a regulatory mechanism similar to that observed in sighted athletes. However, the control mechanism of regulation emerged earlier in non-visually deprived long jumpers and the least visually impaired Class F13 athletes, signifying the importance of visual function in the regulatory stimuli. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to examine the progress of sprint running velocity (SRV) during the initial and secondary acceleration phases in prepubescent (PPS), adolescent (ADS) and adult (AS) sprinters by comparing the progress of the magnitude of the stride length (SL) and stride frequency (SF). SRV, SL and SF progress for each 10-m interval of a 40-m sprinting test were examined with a video-analysis method for a total of thirty-one athletes. A 2 × 4 (age group × 10-m interval) ANOVA with repeated measures on the second factor revealed that SRV was developed similarly in ADS and AS (p > .05) and it was differentiated (p < .05) in PPS due to the limited in distance acceleration phase. Pearson's correlation analysis indicated that SRV and SL were highly correlated (r > .73, p < .05) for the entire distance of the sprinting test for AS and PPS. On the contrary, SF was the main contributor for SRV development in the 10-30m segment for ADS. In conclusion, SRV improvement seemed to be attributed to the increment of SL and SF, which were differently developed in prepubertal, adolescent and adult sprinters in the 40-m sprint. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to present the kinematic characteristics of the last strides, the touchdown and the take-off of junior male and female long jumpers. A digital JVC GR-DVL 9600EG video camera (sampling frequency: 100fields/sec) was used to capture the last two strides of the approach, the touchdown and the take-off of the participants in the finals of the long jump competitions in the Greek National Junior Championships. Kinematic characteristics were obtained utilizing a 2D-DLT analysis, while the technique elements were evaluated according to the Model Technique Analysis Sheet proposed by Tidow (1989). The comparison of the kinematic parameters between male and female jumpers was conducted using independent samples Student's T Test and a Principal Components Analysis with Varimax rotation (Panoutsakopoulos et al., 2007) factor analysis method. Results indicated that the male jumpers, when compared to the female jumpers, performed the long jump with statistical significant (p<.05) larger values in parameters that define the trajectory of the Body Center of Mass during the flight (angle of projection, takeoff velocity, takeoff height). The process of the kinematic data utilizing the factor analysis method revealed that the female athletes were inferior regarding the values of the parameters related to the vertical axis (i.e. vertical take-off velocity). Additionally, female jumpers performed the jump with statistical significant (p<.05) enhanced number of errors regarding the technique elements which were evaluated. In conclusion, the long jump performed by junior male and female athletes was quantitative and qualitative inferior when compared to adult jumpers. Therefore, technique improvement must be in accordance with the development of the parameters of sporting conditioning. [ABSTRACT FROM AUTHOR]

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 6.0kg, 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 maximise propulsion. As a result, the body tries to balance and equalise this movement and move the hip to larger extension. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate the occurrence of stride regulation at the approach phase of the long jump in athletes with normal vision and visually deprived Class F12 and F13 athletes. All the athletes exhibited the presence of a regulatory mechanism. In the normal vision group this occurred on the fifth-to-last stride. In Class F12 athletes regulation commenced on the fourth-to-last stride for males and third-to-last stride for females. Class F13 males commenced regulation, like the control group, on the fifth-to-last stride; but females commenced on the fourth-to-last stride. The study demonstrated that reduced vision does not prevent Class F12 and F13 athletes from applying a regulatory mechanism similar to that observed in sighted athletes. However, the control mechanism of regulation emerged earlier in non-visually deprived long jumpers and the least visually impaired Class F13 athletes, signifying the importance of visual function in the regulatory stimuli. [ABSTRACT FROM AUTHOR]