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1
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Intra-Personal and Inter-Personal Kinetic Synergies During Jumping

100%
Slomka K., Juras G., Sobota G., Furmanek M., Rzepko M., Latash M. L.
Journal of Human Kinetics
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2015
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vol. 49
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issue 1
75-88
EN
We explored synergies between two legs and two subjects during preparation for a long jump into a target. Synergies were expected during one-person jumping. No such synergies were expected between two persons jumping in parallel without additional contact, while synergies were expected to emerge with haptic contact and become stronger with strong mechanical contact. Subjects performed jumps either alone (each foot standing on a separate force platform) or in dyads (parallel to each other, each person standing on a separate force platform) without any contact, with haptic contact, and with strong coupling. Strong negative correlations between pairs of force variables (strong synergies) were seen in the vertical force in one-person jumps and weaker synergies in two-person jumps with the strong contact. For other force variables, only weak synergies were present in one-person jumps and no negative correlations between pairs of force variable for two-person jumps. Pairs of moment variables from the two force platforms at steady state showed positive correlations, which were strong in one-person jumps and weaker, but still significant, in two-person jumps with the haptic and strong contact. Anticipatory synergy adjustments prior to action initiation were observed in oneperson trials only. We interpret the different results for the force and moment variables at steady state as reflections of postural sway.
2
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The Kinetic Specificity of Plyometric Training: Verbal Cues Revisited

100%
Louder T., Bressel M., Bressel E.
Journal of Human Kinetics
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2015
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vol. 49
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issue 1
201-208
EN
Plyometric training is a popular method utilized by strength and conditioning professionals to improve aspects of functional strength. The purpose of this study was to explore the influence of extrinsic verbal cueing on the specificity of jumping movements. Thirteen participants (age: 23.4 ± 1.9 yr, body height: 170.3 ± 15.1 cm, body mass: 70.3 ± 23.8 kg,) performed four types of jumps: a depth jump “as quickly as possible” (DJT), a depth jump “as high as possible” (DJH), a countermovement jump (CMJ), and a squat jump (SJ). Dependent measures, which included measurement of strength and power, were acquired using a force platform. From the results, differences in body-weight normalized peak force (BW) (DJH: 4.3, DJT: 5.6, CMJ: 2.5, SJ: 2.2), time in upward propulsion (s) (DJH: 0.34, DJT: 0.20, CMJ: 0.40, SJ: 0.51), and mean acceleration (m·s-2) (DJH: 26.7, DJT: 36.2, CMJ: 19.8, SJ: 17.3) were observed across all comparisons (p = 0.001 - 0.033). Differences in the body-weight normalized propulsive impulse (BW·s) (DJH: 0.55, DJT: 0.52, CMJ: 0.39, SJ: 0.39) and propulsive power (kW) (DJH: 13.7, DJT: 16.5, CMJ: 11.5, SJ: 12.1) were observed across all comparisons (p = 0.001 - 0.050) except between the CMJ and SJ (p = 0.128 - 0.929). The results highlight key kinetic differences influencing the specificity of plyometric movements and suggest that verbal cues may be used to emphasize the development of reactive strength (e.g. DJT) or high-velocity concentric power (e.g. DJH).
3
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Relationships between Balance and Functional Performance in Football Players

88%
Erkmen N., Taşkin H., Sanioğlu A., Kaplan T., Baştürk D.
Journal of Human Kinetics
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2010
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vol. 26
21-29
EN
The aim of the present study was to examine the relationships between balance performance as measured by the Balance Error Scoring System and functional performance in football players. Twenty-two football players from University League Final Group in Turkey (age 23.05 ± 1.65 years, height 176.58 ± 6.99 cm, weight 68.80 ± 7.00 kg) volunteered to participate in the study. Postural performance was measured by the Balance Error Scoring System (BESS). For functional performance, standing broad jump, triple-hop, vertical jump, four-line sprint and three-corner run test were used. There was not a statistically significant relationship among the all BESS scores and triplehop in non-dominant leg, power, four-line sprint, and three-corner run performances (p<0.05). Triple-hop in dominant leg performance correlated with foam surface, tandem leg and total BESS score (r = 0.755, p < 0.01; r = 0.664, p < 0.05; r = 0.713, p< 0.01, respectively). Standing broad jump performance correlated with foam surface, tandem leg and total BESS score (r = 0.737, p < 0.01; r = 0.692, p < 0.05; r = 0.617, p< 0.05, respectively). There was a statistically significant relationship among the single leg BESS score and vertical jumping performance (r = -0.596, p<0.05). In conclusion, the activities requiring explosive power may reflect the ability of managing a balanced posture but the activities in which time period is longer may not.
4
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Jumping Impairs Visual Feedback Control of Body Position

88%
Zemková E., Hamar D.
Human Movement
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2011
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vol. 12
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issue 3
248-253
EN
Purpose. The aim of this study was to evaluate the effects of maximal rebound jumping on sensorimotor tasks that required visual feedback control in positioning the body. Methods. A group of 14 university students (age 23.7 ± 2.6 y, height 178.6 ± 9.2 cm, and weight 70.6 ± 11.4 kg) had to hit a target that randomly appeared on one side of a screen by horizontally shifting their centre of mass (COM) in the appropriate direction prior to (as a baseline) and after six 60-second maximal jump exercises. Each response test consisted of 60 targets. The time, distance, and the velocity of the centre of pressure (COP) trajectory between the stimulus's appearance and its hit, by visually-guiding the COM movement on the screen, were registered by means of a FiTRO Sway Check system using a dynamometric platform. During the sets of jumps, the power of the concentric phase of take off was registered using a FiTRO Jumper recorder. Results. Results found that after each set of jumping (of around 110 jumps per set), mean response time significantly (p ≤ 0.05) increased from an initial value of 1616 ± 506 ms to 1825 ± 562 ms till the 4th set, with no further increase towards the 6th set. Similarly, the mean distance of COP covered during the response time increased significantly (p ≤ 0.05) from a pre-exercise value of 0.449 ± 0.298 m to 0.550 ± 0.295 m after the 4th set which then plateaued towards the 6th set. However, no significant changes in mean COP velocity were detected. Conclusion. Rebound jumping negatively affected the visual feedback control in positioning the body. However, after the proprioceptive functions deteriorated to a certain level, there was no further impairment on sensorimotor parameters.
5
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Isokinetic Leg Strength and Power in Elite Handball Players

88%
González-Ravé J. M., Juárez D., Rubio-Arias J. A., Clemente-Suarez V. J., Martinez-Valencia M. A., Abian-Vicen J.
Journal of Human Kinetics
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2014
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vol. 41
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issue 1
227-233
EN
Isokinetic strength evaluation of the knee flexion and extension in concentric mode of contraction is an important part of the comprehensive evaluation of athletes. The aims of this study were to evaluate the isokinetic knee peak torque in both the extension and flexion movement in the dominant and non-dominant leg, and the relationship with jumping performance. Twelve elite male handball players from the top Spanish handball division voluntary participated in the study (age 27.68 ± 4.12 years; body mass 92.89 ± 12.34 kg; body height 1.90 ± 0.05 m). The knee extensor and flexor muscle peak torque of each leg were concentrically measured at 60°/s and 180°/s with an isokinetic dynamometer. The Squat Jump and Countermovement Jump were performed on a force platform to determine power and vertical jump height. Non-significant differences were observed between legs in the isokinetic knee extension (dominant= 2.91 ± 0.53 Nm/kg vs non-dominant = 2.70 ± 0.47 Nm/kg at 60°/s; dominant = 1.90 ± 0.31 Nm/kg vs non-dominant = 1.83 ± 0.29 Nm/kg at 180°/s) and flexion peak torques (dominant = 1.76 ± 0.29 Nm/kg vs non-dominant = 1.72 ± 0.39 Nm/kg at 60°/s; dominant = 1.30 ± 0.23 Nm/kg vs non-dominant = 1.27 ± 0.35 Nm/kg at 180°/s). Low and non-significant correlation coefficients were found between the isokinetic peak torques and vertical jumping performance (SJ = 31.21 ± 4.32 cm; CMJ = 35.89 ± 4.20 cm). Similar isokinetic strength was observed between the legs; therefore, no relationship was found between the isokinetic knee flexion and extension peak torques as well as vertical jumping performance in elite handball players.
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