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EN
The eggbeater kick presents an important basic technical skill in water polo. The aim of this study was to examine some different tests in order to recommend the best ones for the evaluation of the eggbeater kick. Twenty eight young male water polo players performed one test (squat jump) on land and ten tests in water: tethered swimming with legs only, using alternating and simultaneous eggbeater kicks, jumps out of water from basic and vertical (arms vertically above the head) position, water start and swimming two meters and swimming horizontally with legs only five meters with a flying start. The differences between tests were checked by executing dependent t-tests, while Pearson"s correlation coefficients were calculated to evaluate the correlation between different parameters. Results showed that when performing alternate eggbeater kicks greater average forces were produced by the water polo players when compared to consecutive simultaneous eggbeater kicks. However, a short time maximal acceleration of the body in the vertical and horizontal plane was greater when the single simultaneous kick was performed. It was determined that horizontal swimming using legs only and a squat jump were less useful for the evaluation of the eggbeater kick. Therefore, the recommendation was to measure the average force of successive alternating eggbeater kicks, the height of the jump out of the water from the basic position and the water start and swim over a distance of 2 meters.
Human Movement
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2011
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tom 12
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nr 4
307-314
EN
Purpose. The aim of this study was to quantitatively investigate the effects of muscle strengthening in a vertical squat jump based on a neuro-musculo-skeletal model and a forward dynamics simulation. Methods. During simulation trials, 16 major muscle groups of the lower extremities were gradually strengthened up to 20%. Results. Complex yet systematic deviations in body kinematics, kinetics and the neural control pattern were observed as a result of gradual muscle strengthening. Conclusions. Based on the generated results it was concluded that: (i) the pattern of kinematical changes depends on which muscles are strengthened, while the magnitude of the changes depends on how much the muscles are strengthened. (ii) Adjustment of muscle coordination, in some cases, can be performed without adjustment of neural control. (iii) The adjustment of neural control is done in an adaptive manner. (iv) Inter-segmental coordination is further altered if a smaller number of muscles are strengthened. (v) The main effect of equally strengthening all the muscles is an increase in joint torque, which is proportional to the increase in muscle strength.
3
Content available remote Effects of a Low-Load Gluteal Warm-Up on Explosive Jump Performance
75%
EN
The purpose of this study was to investigate the effects of a low-load gluteal warm-up protocol on countermovement and squat jump performance. Research by Crow et al. (2012) found that a low-load gluteal warm-up could be effective in enhancing peak power output during a countermovement jump. Eleven subjects performed countermovement and squat jumps before and after the gluteal warm-up protocol. Both jumps were examined in separate testing sessions and performed 30 seconds, and 2, 4, 6 & 8 minutes post warm-up. Height jumped and peak ground reaction force were the dependent variables examined in both jumps, with 6 additional variables related to fast force production being examined in the squat jump only. All jumps were performed on a force platform (AMTI OR6-5). Repeated measures analysis of variance found a number of significant differences (p ≤ 0.05) between baseline and post warm-up scores. Height jumped decreased significantly in both jumps at all rest intervals excluding 8 minutes. Improvement was seen in 7 of the 8 recorded SJ variables at the 8 minute interval. Five of these improvements were deemed statistically significant, namely time to peak GRF (43.0%), and time to the maximum rate of force development (65.7%) significantly decreased, while starting strength (63.4%), change of force in first 100 ms of contraction (49.1%) and speed strength (43.6%) significantly increased. The results indicate that a gluteal warm-up can enhance force production in squat jumps performed after 8 minutes recovery. Future research in this area should include additional warm-up intervention groups for comparative reasons.
EN
ackground. Lower limbs performance plays a huge role in the training processes of martial arts, including taekwondo. By monitoring vertical jumps (VJ) lower limb muscular strength can be assessed. However, the force plate, considered the gold standard device to evaluate VJ performance, is expensive and lab-based. The Polar V800 device is able to measure VJ height, and it has become widely popular among trainers and athletes. However, it has not yet been validated for this purpose. Problem and aim. Due to the impracticability of using the force plate, coaches and athletes have been using the Polar V800 in their training routines. This study aimed to evaluate the validity and reliability of the Polar V800 versus force plate measurements to estimate VJ height in taekwondo athletes. Methods. Thirty male national level taekwondo athletes were asked to perform five squat jumps and five countermovement jumps at maximal effort on the force plate while simultaneously wearing the stride sensor connected to the V800. The mean and the highest jump measurements estimated simultaneously by both devices were compared through Pearson’s correlation and Bland-Altman test. Results. Intraday reliability of the V800 was excellent with ICCs ranging from 0.97 to 0.98. There was strong reliability (ICC > 0.97), a low standard error of measurements (0.69 - 0.92 cm), an excellent correlation between methods (r > 0.96), and excellent agreement observed by Bland-Altman analysis. Conclusion. The Polar V800 device is demonstrated to be a valid and reliable tool for the estimation of VJ height.
PL
Tło. Wydajność kończyn dolnych odgrywa ogromną rolę w procesie treningu sztuk walki, w tym taekwondo. Monitorowanie skoków pionowych (VJ) pozwala na ocenę siły mięśni kończyn dolnych. Jednak talerz do treningu siłowego, uważany za złoty standard urządzenia do oceny wydajności VJ, jest kosztowny i działający w warunkach laboratoryjnych. Urządzenie Polar V800 jest w stanie mierzyć wysokość wyskoku VJ i stało się ono bardzo popularne wśród trenerów i sportowców. Jednak nie uzyskało jeszcze zatwierdzenia. Problem i cel. Ze względu na niepraktyczność talerza do treningu siłowego, trenerzy i sportowcy używają urządzenia Polar V800 w swojej rutynie treningowej. W związku z tym, niniejsze badanie miało na celu ocenę ważności i wiarygodności zastosowania urządzenia Polar V800 z pomiarem siłownika do szacowania wysokości skoku pionowego zawodników taekwondo. Metody. Trzydziestu zawodników taekwondo na poziomie klasy narodowej zostało poproszonych o wykonanie pięciu skoków z przysiadu i pięciu skoków z obrotem przy maksymalnym wysiłku na talerzu do treningu siłowego, przy jednoczesnym użyciu czujnika skoku podłączonego do urządzenia V800. Średnie i najwyższe skoki zostały oszacowane jednocześnie przez oba urządzenia i porównane za pomocą korelacji Pearsona i testu Bland-Altmana. Wyniki. Niezawodność śróddzienna V800 była doskonała przy współczynnikach ICC w zakresie od 0,97 do 0,98. Stwierdzono silną wiarygodność (ICC > 0,97), niski błąd standardowy pomiarów (0,69 - 0,9 cm), doskonałą korelację między metodami (r > 0,96) oraz doskonałą zgodność obserwowaną w analizie Bland-Altmana. Wniosek. Urządzenie Polar V800 okazało się być ważnym i wiarygodnym narzędziem do szacowania wysokości skoku pionowego (VJ).
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