Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 9

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
w słowach kluczowych:  countermovement jump
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
Introduction. The purpose of this study was to compare the acute effects of traditional jumps and rope jumps during warm-up on power and jumping ability in trained men. Material and methods. A group of 12 national-level track and field athletes participated in the study. Peak power and jumping ability were assessed by having participants perform five alternate leg bounds, a countermovement jump (CMJ) and a drop jump (DJ). Three different warm-up protocols were used in random order, with 3-day intervals between them. The first involved traditional jumps, the second rope jumps and the control consisted of general warm-up only (jogging and stretching). Results. The rope-jump warm-up protocol significantly improved jumping distance (p<0.05) as compared to the traditional protocol. There were no significant differences in peak power or jump height among experimental groups in the CMJ and DJ. The study also revealed that traditional and ropejump protocols significantly (p<0.001) increased peak power and jump height for the CMJ and DJ, and jump distance for the five alternate leg bounds compared to the control condition. Conclusion. The results of this study suggest that a warm-up including rope jumps may be more effective for horizontal jumping tasks than a protocol with traditional jumps, and that traditional and rope-jump warm-up protocols provide similar levels of enhancement for vertical jumping tasks.
The aim of the present study was to compare the aerobic and anaerobic power and capacity of elite male basketball players who played multiple positions. Fifty-five healthy players were divided into the following three different subsamples according to their positional role: guards (n = 22), forwards (n = 19) and centers (n = 14). The following three tests were applied to estimate their aerobic and anaerobic power and capacities: the countermovement jump (CMJ), a multistage shuttle run test and the Running-based Anaerobic Sprint Test (RAST). The obtained data were used to calculate the players’ aerobic and anaerobic power and capacities. To determine the possible differences between the subjects considering their different positions on the court, one-way analysis of variance (ANOVA) with the Bonferroni post-hoc test for multiple comparisons was used. The results showed that there was a significant difference between the different groups of players in eleven out of sixteen measured variables. Guards and forwards exhibited greater aerobic and relative values of anaerobic power, allowing shorter recovery times and the ability to repeat high intensity, basketball-specific activities. Centers presented greater values of absolute anaerobic power and capacities, permitting greater force production during discrete tasks. Coaches can use these data to create more individualized strength and conditioning programs for different positional roles.
The main aim of the present study was to analyze the relationships between dry land strength and power measurements with swimming performance. Ten male national level swimmers (age: 14.9 ± 0.74 years, body mass: 60.0 ± 6.26 kg, height: 171.9 ± 6.26, 100 m long course front crawl performance: 59.9 ± 1.87 s) volunteered as subjects. Height and Work were estimated for CMJ. Mean power in the propulsive phase was assessed for squat, bench press (concentric phase) and lat pull down back. Mean force production was evaluated through 30 s maximal effort tethered swimming in front crawl using whole body, arms only and legs only. Swimming velocity was calculated from a maximal bout of 50 m front crawl. Height of CMJ did not correlate with any of the studied variables. There were positive and moderate-strong associations between the work during CMJ and mean propulsive power in squat with tethered forces during whole body and legs only swimming. Mean propulsive power of bench press and lat pull down presented positive and moderate-strong relationships with mean force production in whole body and arms only. Swimming performance is related with mean power of lat pull down back. So, lat pull down back is the most related dry land test with swimming performance; bench press with force production in water arms only; and work during CMJ with tethered forces legs only.
Content available remote Biomechanical Analysis of the Jump Shot in Basketball
Basketball players usually score points during the game using the jump shot. For this reason, the jump shot is considered to be the most important element of technique in basketball and requires a high level of performance. The aim of this study was to compare the biomechanical characteristics of the lower limbs during a jump shot without the ball and a countermovement jump without an arm swing. The differences between variables provide information about the potential that an athlete can utilise during a game when performing a jump shot. The study was conducted among 20 second-league basketball players by means of a Kistler force plate and the BTS SMART system for motion analysis. The variables measured included the take-off time, mean power, peak power, relative mean power, jump height, maximum landing force and calculated impact ratio. Surprisingly, more advantageous variables were found for the jump shot. This finding suggests a very high performance level in the jump shot in the studied group and a maximum utilisation of their motor abilities. Both types of jumps were characterised by high mean and peak power values and average heights. The high forces at landing, which result in considerable impact ratios, may have prompted the studied group to land softly. Use of the countermovement jump without an arm swing is recommended to assess and predict the progression of player’s jumping ability
Purpose: Lower extremity power is an important physical capacity of a soccer athlete. Power represents, and can be modified by, the training of strength and speed. Pre-season and in-season training differs in the relative emphasis on these two quantities. It is nevertheless desirable that the mechanical power remain the same or become higher during the in-season period. The purpose of this study was to identify changes in quantities related to “explosive strength” and to check whether, in collegiate female soccer players, pre- and inseason lower extremity power will remain unaltered. Methods: Twenty collegiate female soccer players, representing all field positions, participated. Lower extremity power was assessed by a series of drop jumps executed from four different heights (15, 30, 45, and 60 cm). Mechanical power was calculated using subject’s mass, jump height, and acceleration due to gravity. This value was further normalized by body mass of each athlete to obtain the relative (or normalized) mechanical power. Results: The normalized lower extremity mechanical power was highest when landing from the 30 cm height for both pre- and inseason periods. However, contrary to expectations, it turned out lower during the in-season than during the pre-season test, even though no significant differences were found between the corresponding jump heights. Conclusions: It is concluded that altered, perhaps inadequate, training strategies were employed during the in-season period. Besides, advantages of adding the relative mechanical power as a season readiness indicator are underlined compared with relying on the jump height alone.
Purpose: The aim of this study was to present the methodology for estimation of a leg stiffness during a countermovement jump. The question was asked whether leg stiffness in the countermovement and take-off phases are similar to each other as demonstrated in previous reports. It was also examined whether the stiffness in left lower limb is similar to the one in right lower limb. Methods: The research was conducted on 35 basketball players. Each participant performed three countermovement jumps with arm swing to the maximum height. Measurements employed a Kistlerforce plate and a BTS SMART system for motion analysis. Leg stiffness (understood as an inclination of the curve of ground reaction forces vs. length) was computed for these parts of countermovement and take-off phases where its value was relatively constant and F(∆l) relationship was similar to linear. Results: Mean value (±SD) of total stiffness of both lower limbs in the countermovement phase was 7.1 ± 2.3 kN/m, whereas this value in the take-off phase was 7.5 ± 1 kN/m. No statistically significant differences were found between the leg stiffness in the countermovement and the take-off phases. No statistically significant differences were found during the comparison of the stiffness in the right and left lower limb. Conclusions: The calculation methodology allows us to estimate the value of leg stiffness based on the actual shape of F(∆l) curve rather than on extreme values of ∆F and ∆l. Despite different tasks of the countermovement and the take-off phases, leg stiffness in these phases is very similar. Leg stiffness during a single vertical jump maintains a relatively constant value in the parts with a small value of acceleration.
The aim of this research was to evaluate the biomechanical parameters of lower limbs and their influence on height of vertical jump. The research was conducted on a group of females practicing basketball and volleyball. The following equipment was used during the experiment: a force plate by Kistler, a Biometrics electrogoniometer and a specially designed chair to measure static torque by OPIW Opole. The results indicated that the jumping abilities of the examined athletes were poor. No statistically significant correlations were observed between knee static torque and heights of vertical jumps: CMJ and DJ. The authors suggest modification of the McClymont index (RSI) to evaluate the selection of platform height during plyometric training. Such modification would enable better choice of loads and better training control of the subject.
Purpose: One inconvenience in finding experimental evidence for the relationship between potential elastic energy and vertical jump height is the difficulty of estimating the value of the stored potential elastic energy. Therefore, the aim of this study is to present a simple method of estimating the potential elastic energy stored by lowering the center of mass during the countermovement phase of a vertical jump. Methods: The research was conducted on 30 able-bodied male university students (age: 20 years, body height: 183.1 ± 7.9 cm, body mass: 80.3 ± 10.4 kg). Each participant performed 10 single countermovement jumps with arms akimbo to maximal height. Measurements employed a Kistler force plate. The value of potential elastic energy was estimated based on the curve of dependence of the ground reaction force on the vertical displacement of the jumper’s center of mass. Results: The mean value (±SD) of potential elastic energy collected due to lowering of the center of mass during the countermovement phase of a vertical jump was 183 ± 69 J. 24.3% of this value can be considered the part of the potential elastic energy (44 ± 21 J) that comes from the transformation of kinetic energy. The total change in gravitational potential energy due to lowering the center of mass was 240 ± 58 J. Conclusions: This estimation of potential elastic energy is only general and rough. However, certain estimations of potential elastic energy may offer some insight into the phenomenon relating vertical quasi-stiffness and the ability to store potential elastic energy with vertical jump height.
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.
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).
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.