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Artículos de revistas sobre el tema "Jumping drops"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 11 de febrero de 2022

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1

Liu, Fangjie, Giovanni Ghigliotti, James J. Feng y Chuan-Hua Chen. "Self-propelled jumping upon drop coalescence on Leidenfrost surfaces". Journal of Fluid Mechanics 752 (2 de julio de 2014): 22–38. http://dx.doi.org/10.1017/jfm.2014.319.

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AbstractSelf-propelled jumping upon drop coalescence has been observed on a variety of textured superhydrophobic surfaces, where the jumping motion follows the capillary–inertial velocity scaling as long as the drop radius is above a threshold. In this paper, we report an experimental study of the self-propelled jumping on a Leidenfrost surface, where the heated substrate gives rise to a vapour layer on which liquid drops float. For the coalescence of identical water drops, we have tested initial drop radii ranging from 20 to $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}500\ \mu \mathrm{m}$, where the lower bound is related to the spontaneous takeoff of individual drops and the upper bound to gravitational effects. Regardless of the approaching velocity prior to coalescence, the measured jumping velocity is around 0.2 when scaled by the capillary–inertial velocity. This constant non-dimensional velocity holds for the experimentally accessible range of drop radii, and we have found no cutoff radius for the scaling, in contrast to prior experiments on textured superhydrophobic surfaces. The Leidenfrost experiments quantitatively agree with our numerical simulations of drop coalescence on a flat surface with a contact angle of 180°, suggesting that the cutoff is likely to be due to drop–surface interactions unique to the textured superhydrophobic surfaces.

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2

Liu, Fangjie, Giovanni Ghigliotti, James J. Feng y Chuan-Hua Chen. "Numerical simulations of self-propelled jumping upon drop coalescence on non-wetting surfaces". Journal of Fluid Mechanics 752 (2 de julio de 2014): 39–65. http://dx.doi.org/10.1017/jfm.2014.320.

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AbstractCoalescing drops spontaneously jump out of plane on a variety of biological and synthetic superhydrophobic surfaces, with potential applications ranging from self-cleaning materials to self-sustained condensers. To investigate the mechanism of self-propelled jumping, we report three-dimensional phase-field simulations of two identical spherical drops coalescing on a flat surface with a contact angle of 180°. The numerical simulations capture the spontaneous jumping process, which follows the capillary–inertial scaling. The out-of-plane directionality is shown to result from the counter-action of the substrate to the impingement of the liquid bridge between the coalescing drops. A viscous cutoff to the capillary–inertial velocity scaling is identified when the Ohnesorge number of the initial drops is around 0.1, but the corresponding viscous cutoff radius is too small to be tested experimentally. Compared to experiments on both superhydrophobic and Leidenfrost surfaces, our simulations accurately predict the nearly constant jumping velocity of around 0.2 when scaled by the capillary–inertial velocity. By comparing the simulated drop coalescence processes with and without the substrate, we attribute this low non-dimensional velocity to the substrate intercepting only a small fraction of the expanding liquid bridge.

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3

Boreyko, Jonathan B. y Chuan-Hua Chen. "Self-propelled jumping drops on superhydrophobic surfaces". Physics of Fluids 22, n.º 9 (septiembre de 2010): 091110. http://dx.doi.org/10.1063/1.3483222.

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4

Terentiev, A. G. "Jumping drops on the surface of the water". Multiphase Systems 15, n.º 3-4 (2020): 228–31. http://dx.doi.org/10.21662/mfs2020.3.135.

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The paper proposes a theoretical model for the bouncing of a water drop on a free surface. The motion of a drop in air is described by the usual equations connecting the forces of inertia, gravity, and Stokes (viscosity resistance). The drop is considered spherical with a given surface tension. Numerical calculations were carried out using the same algorithm, but with different initial conditions. Some conditions are set for the droplet disintegration, others for the droplet reflection from the free surface. It is shown that the disintegration of a drop occurs periodically with a decrease in the drop size and an increase in the drop rise height. In the interval between droplet decays, periodic reflection from the free surface occurs with a decrease in the rise height.

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5

Li, Ning, Lei Wu, Cunlong Yu, Haoyu Dai, Ting Wang, Zhichao Dong y Lei Jiang. "Ballistic Jumping Drops on Superhydrophobic Surfaces via Electrostatic Manipulation". Advanced Materials 30, n.º 8 (9 de enero de 2018): 1703838. http://dx.doi.org/10.1002/adma.201703838.

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6

Liu, T. Q., W. Sun, X. Y. Sun y H. R. Ai. "Mechanism study of condensed drops jumping on super-hydrophobic surfaces". Colloids and Surfaces A: Physicochemical and Engineering Aspects 414 (noviembre de 2012): 366–74. http://dx.doi.org/10.1016/j.colsurfa.2012.08.063.

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7

Wang, Zhantao, Dirk van den Ende, Arjen Pit, Rudy Lagraauw, Daniël Wijnperlé y Frieder Mugele. "Jumping drops on hydrophobic surfaces, controlling energy transfer by timed electric actuation". Soft Matter 13, n.º 28 (2017): 4856–63. http://dx.doi.org/10.1039/c7sm00928c.

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8

Qin, Yi, Jin Jack Tan y Maarten Hornikx. "Experimental investigation of the low-frequency impact sound transfer function of lightweight wooden floors via heel drops". Acta Acustica 4, n.º 6 (2020): 23. http://dx.doi.org/10.1051/aacus/2020022.

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The lightweight floor is a popular construction choice in buildings despite its poor low-frequency impact sound performance. This is exacerbated by common human activities, such as walking and jumping, that have high input force levels at low frequencies. Therefore, experimental evaluations of the low-frequency impact sound performance of a wooden lightweight floor are of interest to designers and researchers. The aim of this paper is to explore the use of heel drop for impact sound transfer measurement. An impact force plate has been built to accurately measure the heel-drop forces up to 200 Hz and the performances on two types of floors are evaluated. The heel drop has a higher energy level at low frequencies, resulting in higher coherence and signal-to-noise ratio and hence superior performance in characterizing the floors in the frequency range of below 40 Hz when compared to the impact hammer. Interestingly, in the case of a heel-drop excitation, the first natural frequencies of the floor decrease. It is in contrast to when a human is simply standing on it, which resulted in an increase of the natural frequencies upon impact hammer excitation.

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9

Fu, Xiang Ting, Yan Zha y An Liang Zhang. "Droplets Transportation on a Piezoelectric Substrate with an Obstacle". Applied Mechanics and Materials 339 (julio de 2013): 104–8. http://dx.doi.org/10.4028/www.scientific.net/amm.339.104.

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A method for a droplet transportation by jumping a obstacle on piezoelectric substrate is presented, and a device for the droplet transportation is implemented on a 128° yx-LiNbO3 piezoelectric substrate. An interdigital transducer and a reflector are fabricated on the piezoelectric substrate using microelectric technology. Hydrophobic film is coated on the area free of electrodes and a polydimethylsilicone obstacle is mounted on it. A radio frequency signal amplified by a power amplifier is applied to the interdigital transducer to generate surface acoustic wave. When the surface acoustic wave meets with the droplet on the piezoelectric substrate during transportation, part of acoustic wave enegy is radiated into the droplet, leading to internal acoustic streaming. Once the radio frequency signal with appropriate amplitude is suddenly decreased, part of the droplet will jump the obstacle due to interial force. Red dye solution drops are demonstrated for transportation experiments. Results show that a droplet can be transported from one side to another of the obstacle on piezoelectric substrate by help of surface acoustic wave. The presented method is helpful for microfluidic system on a piezoelectric substrate.

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10

Chen, Xuejun, Ruijian Guo, Lingming Tang y Xiaochen Zhang. "Study on Ground Collapse of Covered Karst Soil Caves by Sudden Drop of Groundwater". Advances in Civil Engineering 2021 (10 de agosto de 2021): 1–12. http://dx.doi.org/10.1155/2021/7796401.

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In this study, the ellipsoidal soil cave with vertical collapses in the covering karst area is studied. Based on certain assumptions, the mechanical model of karst collapse caused by groundwater drop was established. Then, based on the negative pressure calculation formula of soil cave cavity according to Boyle–Mariotte’s law, the expression of the stability coefficient of the soil cave was proposed. Subsequently, the feasibility of the theoretical formula was verified. The calculation example analyzed the relationship of groundwater parameters and overburden thickness. The results show that when the initial groundwater level is higher than the top of cave, the law between the stability coefficient of soil cave and groundwater drawdown shows the jumping horizontal broken line. Thus, soil cave tends to collapse when the falling groundwater level drops over the vault; when the initial groundwater level ranges from the bottom to the top of the cave body, the stability coefficient and groundwater drawdown show a negative correlation law, the curve is steep at the early stage and then becomes gentle at the latter stage, and the higher the initial groundwater level in the cave is, the greater stability coefficient of soil cave reduces; when the initial groundwater level is lower than the bottom of the cave, the effect of drawdown is limited. In addition, for the small drawdown or low initial groundwater level, the stability coefficient of soil cave first decreases and then increases with the increases in thickness of overburden, and the thinner the overburden is, the greater the drawdown rate is; when the drawdown or the initial groundwater level is higher, the stability coefficient of soil cave positively relates to the thickness of the overburden layer.

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11

Bobbert, Maarten F. "Drop Jumping as a Training Method for Jumping Ability". Sports Medicine 9, n.º 1 (enero de 1990): 7–22. http://dx.doi.org/10.2165/00007256-199009010-00002.

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12

BOBBERT, MAARTEN F., PETER A. HUIJING y GERRIT JAN VAN INGEN SCHENAU. "Drop jumping. I. The influence of jumping technique on the biomechanics of jumping". Medicine & Science in Sports & Exercise 19, n.º 4 (agosto de 1987): 332???338. http://dx.doi.org/10.1249/00005768-198708000-00003.

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13

SAKUMA, Kaoru, Jun NISHIMURA, Koji OHATA y Noriaki ICHIHASHI. "Kinematics Factors Influencing Drop Jumping". Rigakuryoho Kagaku 24, n.º 2 (2009): 263–67. http://dx.doi.org/10.1589/rika.24.263.

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14

Renaudin, A., E. Galopin, V. Thomy, C. Druon y F. Zoueshtiagh. "Creeping, walking and jumping drop". Physics of Fluids 19, n.º 9 (septiembre de 2007): 091111. http://dx.doi.org/10.1063/1.2775412.

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15

Boreyko, Jonathan B., Yuejun Zhao y Chuan-Hua Chen. "Planar jumping-drop thermal diodes". Applied Physics Letters 99, n.º 23 (5 de diciembre de 2011): 234105. http://dx.doi.org/10.1063/1.3666818.

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16

BOBBERT, MAARTEN F., PETER A. HUIJING y GERRIT JAN VAN INGEN SCHENAU. "Drop jumping. II. The influence of dropping height on the biomechanics of drop jumping". Medicine & Science in Sports & Exercise 19, n.º 4 (agosto de 1987): 339???346. http://dx.doi.org/10.1249/00005768-198708000-00004.

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17

Maloney, Sean J., Joanna Richards y Iain M. Fletcher. "A Comparison of Bilateral and Unilateral Drop Jumping Tasks in the Assessment of Vertical Stiffness". Journal of Applied Biomechanics 34, n.º 3 (1 de junio de 2018): 199–204. http://dx.doi.org/10.1123/jab.2017-0094.

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This study sought to compare vertical stiffness during bilateral and unilateral drop jumping. Specifically, the intersession reliabilities and force-deformation profiles associated with each task were to be examined. On 3 occasions, following familiarization, 14 healthy males (age: 22 [2] y; height: 1.77 [0.08] m; and body mass: 73.5 [8.0] kg) performed 3 bilateral, left leg and right leg drop jumps. All jumps were performed from a drop height of 0.18 m on to a dual force plate system. Vertical stiffness was calculated as the ratio of peak ground reaction force (GRF) to the peak center of mass (COM) displacement. Unilateral drop jumping was associated with higher GRF and greater COM displacement (both Ps < .001), but vertical stiffness was not different between tasks when considering individual limbs (P = .98). A coefficient of variation of 14.6% was observed for bilateral vertical stiffness during bilateral drop jumping; values of 6.7% and 7.6% were observed for left and right limb vertical stiffness during unilateral drop jumping. These findings suggest that unilateral drop jumps may exhibit greater reliability than bilateral drop jumps while eliciting similar vertical stiffness. It is also apparent that higher GRFs during unilateral drop jumping are mitigated by increased COM displacement.

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18

Kim, Chang-Kook, Young-Chul Lee, Ga-Ram Choi, Sung-Jin Park, You-Nam Son y Jin-Suk Oh. "Biomechanical Characteristics of Drop Jumping as a Training Method for Jumping Ability". Journal of Sport and Leisure Studies 70 (30 de noviembre de 2017): 659–72. http://dx.doi.org/10.51979/kssls.2017.11.70.659.

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19

Wiedenheft, Kris F., H. Alex Guo, Xiaopeng Qu, Jonathan B. Boreyko, Fangjie Liu, Kungang Zhang, Feras Eid, Arnab Choudhury, Zhihua Li y Chuan-Hua Chen. "Hotspot cooling with jumping-drop vapor chambers". Applied Physics Letters 110, n.º 14 (3 de abril de 2017): 141601. http://dx.doi.org/10.1063/1.4979477.

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20

Gu, Chin-Yi, Xiang-Rui Li, Chien-Ting Lai, Jin-Jiang Gao, I.-Lin Wang y Li-I. Wang. "Sex Disparity in Bilateral Asymmetry of Impact Forces during Height-Adjusted Drop Jumps". International Journal of Environmental Research and Public Health 18, n.º 11 (1 de junio de 2021): 5953. http://dx.doi.org/10.3390/ijerph18115953.

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Side-to-side asymmetry of lower extremities may influence the risk of injury associated with drop jump. Moreover, drop heights using relative height across individuals based on respective jumping abilities could better explain lower-extremity loading impact for different genders. The purpose of the current study was to evaluate the sex differences of impact forces and asymmetry during the landing phase of drop-jump tasks using drop heights, set according to participants’ maximum jumping height. Ten male and ten female athletes performed drop-jump tasks on two force plates, and ground reaction force data were collected. Both feet needed to land entirely on the dedicated force plates as simultaneously as possible. Ground reaction forces and asymmetry between legs were calculated for jumps from 100%, 130%, and 160% of each participant’s maximum jumping height. Females landed with greater asymmetry at time of contact initiation and time of peak impact force and had more asymmetrical peak impact force than males. Greater values and shorter time after ground contact of peak impact force were found when the drop height increased to 160% of maximum jumping ability as compared to 100% and 130%. Females exhibited greater asymmetry than males during drop jumps from relative heights, which may relate to the higher risk of anterior cruciate ligament injury among females. Greater sex disparity was evident in impact force asymmetry than in the magnitude of peak impact force; therefore, it may be a more appropriate field-screening test for risk of anterior cruciate ligament injury.

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21

Ducrocq, Guillaume P., Thomas J. Hureau, Olivier Meste y Grégory M. Blain. "Similar Cardioventilatory but Greater Neuromuscular Stimuli With Interval Drop Jump Than With Interval Running". International Journal of Sports Physiology and Performance 15, n.º 3 (1 de marzo de 2020): 330–39. http://dx.doi.org/10.1123/ijspp.2019-0031.

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Context: Drop jumps and high-intensity interval running are relevant training methods to improve explosiveness and endurance performance, respectively. Combined training effects might, however, be achieved by performing interval drop jumping. Purpose: To determine the acute effects of interval drop jumping on oxygen uptake ()—index of cardioventilatory/oxidative stimulation level and peripheral fatigue—a limiting factor of explosiveness. Methods: Thirteen participants performed three 11-minute interval training sessions during which they ran 15 seconds at 120% of the velocity that elicited maximal () (ITrun), or drop jumped at 7 (ITDJ7) or 9 (ITDJ9) jumps per 15 seconds, interspersed with 15 seconds of passive recovery. and the time spent above 90% of () were collected. Peripheral fatigue was quantified via preexercise to postexercise changes in evoked potentiated quadriceps twitch (ΔQT). Power output was estimated during ITDJs using optical sensors. Results: All participants reached 90% of or higher during ITrun and ITDJ9, but only 11 did during ITDJ7. was not different between ITrun and ITDJ9 (145 [76] vs 141 [151] s; P = .92) but was reduced during ITDJ7 (28 [26] s; P = .002). Mean ΔQT in ITDJ9 and ITDJ7 was not different (−17% [9%] vs −14% [8%]; P = .73) and greater than in ITrun (−8% [7%]; P = .001). No alteration in power output was found during ITDJs (37 [10] W·kg−1). Conclusion: Interval drop jumping at a high work rate stimulated the cardioventilatory and oxidative systems to the same extent as interval running, while the exercise-induced increase in fatigue did not compromise drop jump performance. Interval drop jumping might be a relevant strategy to get concomitant improvements in endurance and explosive performance.

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22

Kollias, Iraklis, Vassilios Panoutsakopoulos y Georgios Papaiakovou. "Comparing Jumping Ability Among Athletes of Various Sports: Vertical Drop Jumping From 60 Centimeters". Journal of Strength and Conditioning Research 18, n.º 3 (agosto de 2004): 546–50. http://dx.doi.org/10.1519/00124278-200408000-00027.

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23

Kollias, Iraklis, Vassilios Panoutsakopoulos y Georgios Papaiakovou. "Comparing Jumping Ability Among Athletes of Various Sports: Vertical Drop Jumping From 60 Centimeters". Journal of Strength and Conditioning Research 18, n.º 3 (2004): 546. http://dx.doi.org/10.1519/1533-4287(2004)18<546:cjaaao>2.0.co;2.

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24

Dar, Gali y Einat Mei-Dan. "Immediate effect of infrapatellar strap on pain and jump height in patellar tendinopathy among young athletes". Prosthetics and Orthotics International 43, n.º 1 (13 de agosto de 2018): 21–27. http://dx.doi.org/10.1177/0309364618791619.

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Background: Infrapatellar strapping is a treatment technique used in various knee pathologies; however, its effect on pain and functional performance among young athletes has not been studied. Objectives: To evaluate the effect of infrapatellar strap on pain and jumping performance among young athletes diagnosed with patellar tendinopathy. Study design: Pre-/post-test (within-subject research design). Methods: A total of 16 young male basketball and volleyball athletes (age range, 12–18 years) diagnosed with patellar tendinopathy were included in the study. Infrapatellar strap was applied beneath the patella, over the patellar tendon. The athletes performed four jumping tests: squat jump, drop jump, single-leg jump, and jumps 30 s test, with and without the strap. Pain severity in the symptomatic knee during jumping was assessed using a visual analog scale and jumping performance parameters were assessed using an Optojump Next optical measurement system. Results: Pain severity reported by the participants decreased in drop test, single-leg jump test, and jumps 30 s test while using the infrapatellar strap compared with no strap condition ( p < 0.05). No significant difference in jumping performance was found between jumping with and without the strap. Conclusion: The infrapatellar strap was effective in reducing local pain among young male athletes without altered jumping performance. Clinical relevance The infrapatellar strap can be recommended to use during physical activity as part of the physical therapy treatments for patellar tendinopathy. Given the low cost, ease to use, and being a non-invasive method without adverse effects, it is an appropriate intervention for young athletes.

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25

FOWLER, N. E., A. LEES y T. REILLY. "Spinal shrinkage in unloaded and loaded drop-jumping". Ergonomics 37, n.º 1 (enero de 1994): 133–39. http://dx.doi.org/10.1080/00140139408963631.

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26

Boreyko, Jonathan B. y C. Patrick Collier. "Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces". ACS Nano 7, n.º 2 (8 de enero de 2013): 1618–27. http://dx.doi.org/10.1021/nn3055048.

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27

Terzis, Gerasimos, Konstantinos Spengos, Giorgos Karampatsos, Panagiota Manta y Giorgos Georgiadis. "Acute Effect of Drop Jumping on Throwing Performance". Journal of Strength and Conditioning Research 23, n.º 9 (diciembre de 2009): 2592–97. http://dx.doi.org/10.1519/jsc.0b013e3181b1b1a3.

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28

Liu, Jiepeng, Shu Huang, Jiang Li y Y. Frank Chen. "Vibration Behavior of Composite Slab with Precast Ribbed Panels due to Transient Impact". International Journal of Structural Stability and Dynamics 19, n.º 12 (diciembre de 2019): 1950148. http://dx.doi.org/10.1142/s0219455419501487.

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Excessive floor vibrations due to human activities such as heel-drop and jumping can induce annoyance to occupants and cause a serious serviceability problem. Both field tests and finite element analysis were conducted to study the vibration behavior of the composite slab with precast ribbed panels (CSPRP), a relatively new floor system compared with the cast-in-place reinforced concrete (RC) slab. In addition, both heel-drop and jumping impacts were employed to generate the acceleration response of the floor, from which two important vibration characteristics of natural frequencies and damping ratios are obtained. A comparison of the vibration behavior of CSPRPs with RC slabs indicates that the former exhibits more satisfactory perceptibility in terms of vibration. Appropriate coefficients (i.e. [Formula: see text] and [Formula: see text]) with the root-mean-square and peak accelerations subjected to heel-drop and jumping excitations are proposed for both CSPRPs and RC slabs. Lastly, an extensive parametric study considering different boundary conditions, floor types, and floor spans was carried out using the finite element method. It is recommended to use CSPRP under 3.3[Formula: see text]m span in order to keep the fundamental frequency above 3.0[Formula: see text]Hz.

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29

Pääsuke, Mati, Jaan Ereline y Helena Gapeyeva. "Knee Extensor Muscle Strength and Vertical Jumping Performance Characteristics in Pre- and Post-Pubertal Boys". Pediatric Exercise Science 13, n.º 1 (febrero de 2001): 60–69. http://dx.doi.org/10.1123/pes.13.1.60.

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Knee extensor muscle strength and vertical jumping performance characteristics were compared between 14 pre-pubertal (11-year-old) and post-pubertal (16-year-old) boys. Post-pubertal boys had greater (p < .05) absolute values of maximal isometric force (MF) and rate of force development (RFD), absolute and body mass-related values of isokinetic peak torque of the knee extensor muscles at angular velocities of 60, 180, and 240° · s−1, as well as jumping height in squat, counter-movement, and drop jumps, than pre-pubertal boys. This study indicated an inability to use the positive effect of stretch-shortening cycle to vertical jumping performance in pre- and post-pubertal boys.

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30

Hudson, Jackie L. "Performance Excellence: Drop, Stop, Pop: Keys to Vertical Jumping". Strategies 3, n.º 6 (junio de 1990): 11–14. http://dx.doi.org/10.1080/08924562.1990.11000256.

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31

KOV??CS, ISTV??N, J??ZSEF TIHANYI, PAUL DEVITA, LEVENTE R??CZ, JASON BARRIER y TIBOR HORTOB??GYI. "Foot placement modifies kinematics and kinetics during drop jumping". Medicine & Science in Sports & Exercise 31, n.º 5 (mayo de 1999): 708–16. http://dx.doi.org/10.1097/00005768-199905000-00014.

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32

Fowler, Neil E. y Adrian Lees. "The influence of drop height and external loading on performance in drop-jumping". Journal of Biomechanics 27, n.º 6 (enero de 1994): 665. http://dx.doi.org/10.1016/0021-9290(94)90974-1.

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33

Hatze, Herbert. "Validity and Reliability of Methods for Testing Vertical Jumping Performance". Journal of Applied Biomechanics 14, n.º 2 (mayo de 1998): 127–40. http://dx.doi.org/10.1123/jab.14.2.127.

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The validity and reliability of the jumping ergometer method for evaluating performance in two-legged vertical countermovement and serial rebound jumps were investigated. The internal segmental and nonvertical energy flow components for drop jumps were also studied. The exact dynamic equations governing the jumping motion in three dimensions were derived and used together with the approximate relations of the jumping ergometer method to evaluate a total of 72 vertical jumps of different types executed by 22 subjects (15 males, 7 females), average age 24.59 years. The force-plate method was selected as a reference procedure, to which the jumping ergometer results were related. For countermovement jumps, the relative error for jumping height was 3.55% (±2.92%), and for average power per kilogram body mass during the propulsion phase it was 23.79% (±4.85%). For serial rebound jumps, the respective errors were 7.40% (±4.58%) and 5.09% (±4.48%). Internal and nonvertical energy flow components amounted to about 3% of the total. It was concluded that, because of a number of invalid assumptions, unpredictable errors, and contradictory performance requirements, the validity and reliability of the jumping ergometer method for evaluating certain aspects of athletic performance are highly questionable.

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34

Judex, Stefan y Ronald F. Zernicke. "High-impact exercise and growing bone: relation between high strain rates and enhanced bone formation". Journal of Applied Physiology 88, n.º 6 (1 de junio de 2000): 2183–91. http://dx.doi.org/10.1152/jappl.2000.88.6.2183.

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We investigated whether high-impact drop jumps could increase bone formation in the middiaphyseal tarsometatarsus of growing rooster. Roosters were designated as sedentary controls ( n = 10) or jumpers ( n = 10). Jumpers performed 200 drop jumps per day for 3 wk. The mechanical milieu of the tarsometatarsus was quantified via in vivo strain gauges. Indexes of bone formation and mechanical parameters were determined in each of twelve 30° sectors subdividing the middiaphyseal cortex. Compared with baseline walking, drop jumping produced large peak strain rates (+740%) in the presence of moderately increased peak strain magnitudes (+30%) and unaltered strain distributions. Bone formation rates were significantly increased by jump training at periosteal (+40%) and endocortical surfaces (+370%). Strain rate was significantly correlated with the specific sites of increased formation rates at endocortical but not at periosteal surfaces. Previously, treadmill running did not enhance bone growth in this model. Comparing the mechanical milieus produced by running and drop jumps revealed that jumping significantly elevated only peak strain rates. This further emphasized the sensitivity of immature bone to high strain rates.

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35

Katsikari, K., Eleni Bassa, Dimitrios Skoufas, Savvas Lazaridis, Christos Kotzamanidis y Dimitrios A. Patikas. "Kinetic and Kinematic Changes in Vertical Jump in Prepubescent Girls After 10 Weeks of Plyometric Training". Pediatric Exercise Science 32, n.º 2 (1 de mayo de 2020): 81–88. http://dx.doi.org/10.1123/pes.2019-0188.

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Purpose: To examine the effect of a 10-week plyometric training (PT) on the kinematic and kinetic properties of prepubescent girls during squat jump, countermovement jump, and drop jumps. Methods: Twenty-four untrained girls (aged 9–11 y) were assigned to a training group (TG) and a control group. The TG followed twice a week PT for 10 weeks. Squat jump, countermovement jump, and drop jumps performed from heights of 20, 35, and 50 cm were tested before and after PT. Jump height, kinematic, and kinetic parameters were evaluated using a motion analysis system and a force plate. Results: Jumping height in all jump types increased significantly after PT for the TG (P < .001). After training, the TG presented increased power (P < .001) and knee angular velocity (P < .001), higher knee flexion at the deepest point during the braking phase (P < .001), longer contact time (P < .001), and unchanged stiffness and reaction strength index (P > .05). No differences were observed in the control group (P > .05). Conclusion: These findings indicate that a 10-week PT positively affected jumping performance in prepubescent girls who improved their drop jump performance after training not by adopting a stiff/bouncing jumping style of short contact time and increased stiffness, but a compliant/absorbing style of prolonged contact time.

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Motoshima, Yoshie, Daisuke Komori, Junichi Kitagawa y Akira Maeda. "Influence of differences in take-off surface hardness on rebound drop jumping skills and jumping movements of gymnasts and field jumping/combined athletes". Taiikugaku kenkyu (Japan Journal of Physical Education, Health and Sport Sciences) 61, n.º 1 (2016): 1–10. http://dx.doi.org/10.5432/jjpehss.15009.

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Shin, Jae-Min. "Kinematic and Kinetic Differences during the Landing Phase between Drop Landing and Drop Jumping". Journal of Sport and Leisure Studies 67 (28 de febrero de 2017): 467–77. http://dx.doi.org/10.51979/kssls.2017.02.67.467.

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Schmitt, S., A. Grunendahl, F. Mayer y A. Gollhofer. "A biomechanical analysis of human calcanei loads in drop jumping". Journal of Biomechanics 39 (enero de 2006): S177. http://dx.doi.org/10.1016/s0021-9290(06)83625-0.

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39

Makaruk, Hubert, Jason B. Winchester, Adam Czaplicki, Tomasz Sacewicz, Janusz Zieliński y Jerzy Sadowski. "Effects of Assisted and Traditional Drop Jumps on Jumping Performance". International Journal of Sports Science & Coaching 9, n.º 5 (octubre de 2014): 1217–25. http://dx.doi.org/10.1260/1747-9541.9.5.1217.

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Boreyko, Jonathan B. y Chuan-Hua Chen. "Vapor chambers with jumping-drop liquid return from superhydrophobic condensers". International Journal of Heat and Mass Transfer 61 (junio de 2013): 409–18. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.01.077.

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Jørgensen, Stian Langgård, Jens Bojsen‐Møller, Thue Skalgard, Henrik B. Olsen y Per Aagaard. "Dual vs single force plate analysis of human drop jumping". Translational Sports Medicine 4, n.º 5 (17 de mayo de 2021): 637–45. http://dx.doi.org/10.1002/tsm2.255.

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Wang, I.-Lin, Yi-Ming Chen, Ke-Ke Zhang, Yu-Ge Li, Yu Su, Chou Wu y Chun-Sheng Ho. "Influences of Different Drop Height Training on Lower Extremity Kinematics and Stiffness during Repetitive Drop Jump". Applied Bionics and Biomechanics 2021 (3 de marzo de 2021): 1–9. http://dx.doi.org/10.1155/2021/5551199.

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Drop jump (DJ) is often used as a plyometric exercise to improve jumping performance. Training from improper drop heights and for improper durations lead to unfavorable biomechanical changes in the lower extremities when landing, which result in reduced training effects and even lower extremity injuries. Purpose. To study the effects of repeated DJ training at drop heights of 30 cm, 40 cm, and 50 cm (drop jump height (DJH) 30, DJH40, and DJH50) on lower extremity kinematics and kinetics. The 1st, 50th, 100th, 150th, and 200th DJs (DJ1, DJs50, DJs100, DJs150, and DJs200) were recorded by using a BTS motion capture system and force platform. The MATLAB software was used to compare the kinematic and stiffness data of DJ1, DJs50, DJs100, DJs150, and DJs200 with one-way ANOVA repeated measure. If there were significant differences, the LSD method was used for post hoc comparisons. Methods. Twenty healthy male Division III athlete volunteers were selected as subjects, and 200 drop jumps (DJs200) were performed from DJH30, DJH40, and DJH50. Results. The jumping height (JH), contact time (CT), and GRF increased with drop height, and the stiffness of the legs and ankle at DJH30 was higher than that at DJH40 and DJH50 ( p < 0.05 ). Conclusion. Within DJs200, training at DJH50 yield the high impact easily leads to lower extremity injury; training at DJH30 can increase the stiffnesses of the legs and ankle joints, thus effectively utilizing the SSC benefits to store and release elastic energy, reducing the risk of lower extremity musculoskeletal injury. Therefore, coaches can choose different drop heights and training quantities for each person to better prevent lower extremity injury.

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Morikawa, Masanori, Noriaki Maeda, Makoto Komiya, Arisu Hirota, Rami Mizuta, Toshiki Kobayashi, Kazuki Kaneda, Yuichi Nishikawa y Yukio Urabe. "Contribution of Plantar Fascia and Intrinsic Foot Muscles in a Single-Leg Drop Landing and Repetitive Rebound Jumps: An Ultrasound-Based Study". International Journal of Environmental Research and Public Health 18, n.º 9 (23 de abril de 2021): 4511. http://dx.doi.org/10.3390/ijerph18094511.

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The plantar fascia and intrinsic foot muscles (IFM) modulate foot stiffness. However, it is unclear whether the corresponding ultrasonography findings reflect it. This study aimed to examine the effect of the plantar fascia and IFM morphologies on force attenuation during landing and reactivity when jumping in healthy adults (n = 21; age, 21–27 years). Thickness, cross-sectional area (CSA), and hardness of the plantar fascia, abductor hallucis (AbH), and flexor hallucis brevis (FHB) muscles were measured using ultrasonography. Single-leg drop landing and repetitive rebound jumping tests assessed the ground reaction force (GRF) and reactive jump index (RJI), respectively. The CSA of FHB was negatively correlated with maximum vertical GRF (r = −0.472, p = 0.031) in the single-leg drop landing test. The CSA of AbH was negatively correlated with contact time (r = −0.478, p = 0.028), and the plantar fascia thickness was positively correlated with jump height (r = 0.615, p = 0.003) and RJI (r = 0.645, p = 0.002) in the repetitive bound jump test. In multivariate regression analysis, only the plantar fascia thickness was associated with RJI (β = 0.152, 95% confidence interval: 7.219–38.743, p = 0.007). The CSA of FHB may contribute to force attenuation during landing. The thickness of the plantar fascia and CSA of AbH may facilitate jumping high with minimal contact time.

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Makaruk, Hubert. "ACUTE EFFECTS OF ROPE JUMPING WARM-UP ON POWER AND JUMPING ABILITY IN TRACK AND FIELD ATHLETES". Polish Journal of Sport and Tourism 20, n.º 3 (1 de septiembre de 2013): 200–204. http://dx.doi.org/10.2478/pjst-2013-0018.

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Abstract 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.

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Et. al., Enkeleida Lleshi,. "Impact of Drop Jump Index For17-18 Year Old Volleyball Players in Albania". Psychology and Education Journal 58, n.º 3 (14 de abril de 2021): 4008–13. http://dx.doi.org/10.17762/pae.v58i3.4607.

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Volleyball is characterized by the activity of vertical jump performance in the technical elements of attack, block and service. The study focuses on young Female & Male players during the 12-week plyometric training. The objective of this study is to evaluate the effects of 12-weeks plyometric training performance in volleyball players M & F in Albania to see the differences between them. Methods; 40 young players (F & M) participated in this study. N=10 M & N=10 F volleyball players considered as Experimental and the same number as Control. The average age of players included in this study is 17-18 years old. The players of both groups were evaluated before and after 12 weeks. The F&M Experimental groups conducted 12 weeks of plyometric training with 2 sessions for a week. The F&M Control groups conducted the training according to the method of their trainers. Besides anthropometric measurements they developed Drop Jump tests by jumping from the cube in height 40 cm and 60 cm. Results; The results showed a high correlation coefficient (r = 0,924) and statistically significant (p <0,05). Data obtained from two groups GRFP show that the relationship between the contact time and the time air changes between the two tests DJ 40-60cm. Conclusions. The methodology used helps us compare the high and poor performances that help coaches to program more detailed plyometric training for the development of jumping skills in young volleyball players. The effect of plyometric training developed on M&F volleyball players and according to data obtained from GRFP, showed that male volleyball players had a better performance in vertical jump than female volleyball players. Vertical jumping may be assessed not only by the height of its development but also by the phase of residence in the air.

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Böhm, Harald, Gerald K. Cole, Gert-Peter Brüggemann y Hanns Ruder. "Contribution of Muscle Series Elasticity to Maximum Performance in Drop Jumping". Journal of Applied Biomechanics 22, n.º 1 (febrero de 2006): 3–13. http://dx.doi.org/10.1123/jab.22.1.3.

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The contribution of muscle in-series compliance on maximum performance of the muscle tendon complex was investigated using a forward dynamic computer simulation. The model of the human body contains 8 Hill-type muscles of the lower extremities. Muscle activation is optimized as a function of time, so that maximum drop jump height is achieved by the model. It is shown that the muscle series elastic energy stored in the downward phase provides a considerable contribution (32%) to the total muscle energy in the push-off phase. Furthermore, by the return of stored elastic energy all muscle contractile elements can reduce their shortening velocity up to 63% during push-off to develop a higher force due to their force velocity properties. The additional stretch taken up by the muscle series elastic element allows only m. rectus femoris to work closer to its optimal length, due to its force length properties. Therefore the contribution of the series elastic element to muscle performance in maximum height drop jumping is to store and return energy, and at the same time to increase the force producing ability of the contractile elements during push-off.

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BOOCOCK, M. G., G. GARBUTT, K. LINGE, T. REILLY y J. D. G. TROUP. "Changes in stature following drop jumping and post-exercise gravity inversion". Medicine & Science in Sports & Exercise 22, n.º 3 (junio de 1990): 385???390. http://dx.doi.org/10.1249/00005768-199006000-00016.

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Jaén-Carrillo, Diego, Antonio Cartón-Llorente, Demetrio Lozano-Jarque, Alberto Rubio-Peirotén, Luis E. Roche-Seruendo y Felipe García-Pinillos. "Relationship between Reactive Strength and Leg Stiffness at Submaximal Velocity: Effects of Age on Distance Runners". International Journal of Environmental Research and Public Health 18, n.º 13 (26 de junio de 2021): 6866. http://dx.doi.org/10.3390/ijerph18136866.

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Background: Musculotendinous reactive strength is a key factor for the utilization of elastic energy in sporting activities such as running. AIM: To evaluate the relationship between musculotendinous reactive strength and lower-limb stiffness during running as well as to identify age-related differences in both variables. Methods: Fifty-nine amateur endurance runners performed three 20-cm drop jumps and a constant 3-min easy run on a motorized treadmill. Reactive strength index and dynamic lower-limb stiffness were calculated with a photoelectric cell system by jumping and running, respectively. Additionally, sit to stand difference in plantar arch height was assessed as a static lower-limb stiffness measure. The cluster analysis allows the comparison between younger and older runners. Results: No significant correlations were found between jumping reactive strength and running lower-limb stiffness. The younger group performed better at drop jumps (p = 0.023, ES = 0.82), whereas higher-but-no-significant results were found for reactive strength index and stiffness-related metrics. Conclusions: Musculotendinous vertical reactiveness may not be transferred to combined vertical and horizontal movements such as running.

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Göktepe, Mehmet, Meral Miyaç Göktepe, Ferhat Güder y Mehmet Günay. "The effects of core training given to female soccer players on different vertical jumping methods". Journal of Human Sciences 16, n.º 3 (7 de agosto de 2019): 791–98. http://dx.doi.org/10.14687/jhs.v16i3.5637.

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This study aims to determine the effects of core training given to female soccer players on their methods of different vertical jumping. 16 female certified soccer players playing in the female soccer team of Bartın University with average age of 21.07±3.56 years, average height of 163.00±7.18 cm and with weight of 56.60±7.15 kg were included in the study on the basis of volunteering. Prior to the tests, all the female soccer players completed a survey form used in determining their medical status and filled in a form to confirm that they participated in the study voluntarily. The core training programme was applied for 8 weeks two times a week regularly. The pre-test and post-test measurements were made and then subjects’ height and weight were measured, they were asked to run for 10 minutes for warm-up and the activity was ended by making jumping measurement. The research was performed in the physiology laboratory of Bartın University School of Physical Education and Sport (BESYO). Statistical evaluation was made by using SPSS 22.0 programme. The values obtained were compared after checking normality distribution through Shapiro-Wilk test with the help of Wilcoxon signed rank test. This study, we aimed to determine the effect of core strength training on different vertical jump methods applied to female soccer players. It has been observed that it has a favorable effect on counter movement jumping (CMJ) and static jumping (SJ) values (p <0.05). It was found that there was no statistically significant effect on drop jumping (DJ) values (p> 0.05). As a result; It can be said that the core strength training practiced in female soccer players developed counter movement jumpingand static jumping characteristic of vertical jumping methods and did not affect the drop jumpingfeature. In line with these results, it is recommended to take into account the core training programs because the strength training that will be applied in female soccer players can improve the counter movement jumping and static jumping feature. Extended English summary is in the end of Full Text PDF (TURKISH) file. Özet Bu araştırmanın amacı, kadın futbolculara uygulanan kor kuvvet antrenmanlarının farklı dikey sıçrama yöntemlerine etkisinin belirlenmesidir. Çalışmaya Bartın Üniversitesi Kadın Futbol Takımında lisanslı, yaş ortalamaları 21,07±3,56 yıl, boy ortalamaları 163,00±7,18 (cm) ve vücut ağırlıkları 56,60±7,15 (kg) olan gönüllü 16 kadın futbolcu dahil edilmiştir. Testlerden önce araştırmaya katılan kadın futbolcular sağlık durumlarını belirtir sağlık anketini ve gönüllü katılım formunu doldurup imzalamışlardır. Kor antrenman programı 8 hafta boyunca, haftada 2 gün düzenli olarak uygulanmıştır. Çalışmaya katılan kadın futbolculara sırasıyla; boy ve vücut ağırlığı ölçümü yapıldı. 10 dakika ısınma koşusu yaptırıldıktan sonra, sıçrama ölçümleri yapılarak çalışma sonlandırıldı. Bu araştırma Bartın Üniversitesi BESYO Fizyoloji Laboratuvarında yapılmıştır. İstatistiksel değerlendirme SPSS 22.0 programı kullanılarak yapıldı. Ön test ve son testten elde edilen değerler, Shapiro-Wilk testi ile normallik dağılımına bakıldıktan sonra Wilcoxon İşaretli Sıralar testi yardımı ile istatistiksel olarak karşılaştırılmıştır. Çalışmamızın bulgularına göre; kadın futbolculara uygulanan kor kuvvet antrenmanlarının farklı dikey sıçrama yöntemlerine etkisinin belirlenmesi amacıyla yapmış olduğumuz çalışmamızda uygulanan kor kuvvet antrenmanlarının dikey sıçrama yöntemlerinden; yaylanarak sıçrama (YS) ve statik sıçrama (SS) değerlerine olumlu düzeyde etki ettiği gözlemlenmiştir (p<0.05). Düşerek sıçrama (DS) değerlerine ise istatistiksel olarak etkisinin olmadığı tespit edilmiştir (p>0.05). Sonuç olarak; kadın futbolcularda uygulanan kor kuvvet antrenmanlarının dikey sıçrama yöntemlerinden statik sıçrama ve yaylanarak sıçrama özelliğini geliştirdiği, düşerek sıçrama özelliğine ise etki etmediği söylenebilir. Bu sonuçlar doğrultusunda kadın futbolcularda uygulanacak kor kuvvet antrenmanlarının statik sıçrama ve yaylanarak sıçrama özelliğine olumlu yönde etkisi olabileceğinden antrenman programlarında göz önünde bulundurulması önerilebilir.

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Tian-Qing, LIU, SUN Wei, SUN Xiang-Yu y AI Hong-Ru. "Mechanism and Condition Analysis of Condensed Drop Jumping on Super-Hydrophobic Surfaces". Acta Physico-Chimica Sinica 28, n.º 05 (2012): 1206–12. http://dx.doi.org/10.3866/pku.whxb201202293.

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