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1

Fatigue alters the biomechanical contribution of lower extremity joints during a stretch-shortening cycle task

Sun Xiaole, Xia Rui, Zhang Ximi, Zhen Luo, Fu Weijie

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 2

11--19

EN

This study aimed to explore the effect of fatigue on the biomechanical contribution of the lower extremity joints during a typical stretch-shortening cycle (SSC) task. Methods: 15 male athletes completed drop jump (DJ) under pre- and post-fatigue. Vicon motion capture system and 3D Kistler force plates were used to collect kinematics and ground reaction force data simultaneously. Results: Under fatigue condition, 1) the DJ height decreased; the touchdown angle of knee and ankle reduced and the range of motion increased; 2) the maximum push-off moment and power of knee was reduced; 3) the stiffness of knee, ankle, and legs was reduced; 4) the energy generation and the net energy of the ankle decreased; 5) the energy contribution of knee decreased during the eccentric phase. Conclusions: Fatigue altered biomechanical contribution of the lower extremity joints by changing the movement pattern during DJ. The control ability of the knee and ankle were decreased. Eventually, the jump performance was reduced. In addition, the decrease of stiffness as well as the energy contribution of these joints can be used as sensitive indices to evaluate the performance of DJ after fatigue.

2

Lower extremity power in female soccer athletes : a pre-season and in-season comparison

Pietraszewski B., Siemieński A., Bober T., Struzik A., Rutkowska-Kucharska A., Nosal J., Rokita A.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 3

129--135

EN

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.

3

Evaluation of selected biomechanical parameters in female team sports players

Pietraszewski B., Struzik A.

Acta of Bioengineering and Biomechanics

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2013

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Vol. 15, no. 4

103--108

EN

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.

4

Relative power of the lower limbs in drop jump

Pietraszewski B., Rutkowska-Kucharska A.

Acta of Bioengineering and Biomechanics

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2011

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Vol. 13, no. 1

13-18

EN

The purpose of this paper was to determine the power produced by the lower limbs in the take-off phase in drop jumps (DJ) and the correlation between the power and load measured by dropping height after take-off. The research group (N = 17) contained students practicing football, volleyball, basketball, athletics, high jump, swimming and fencing. The individual characteristics "power-load" of the players and the observation of the changes during the training process enable the coaches to choose precise loads and at the same time to improve the training. The criterion of choosing loads in the plyometric training may be relative power output of lower limbs referred to the DJ height. While the condition allowing player to perform this type of training may depend on obtaining greater power in drop jump than in counter movement jump.

5

Effect of increased load on vertical jump mechanical characteristics in acrobats

Król H., Mynarski W.

Acta of Bioengineering and Biomechanics

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2010

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Vol. 12, no. 4

33-37

EN

In this study, we attempt to answer the following question: To what degree the higher muscular activity determined by increased load in the extension phase (eccentric muscle action) of vertical jump affects its efficiency? Ten high performance acrobats participated in this investigation. The acrobats performed tests that consisted of five single “maximal” standing vertical jumps (counter movement jump – CMJ) and five single vertical jumps, in which the task was to touch a bar placed over the jumping acrobats (special counter movement jump – SCMJ). Subsequently, they performed five single drop jumps from an elevation of 0.40 m (DJ). Ground reaction forces were registered using the KISTLER 9182C force platform. MVJ software was used for signal processing [1] and enabling calculations of kinematic and kinetic parameters of the subject’s jumping movements (on-line system). The results obtained show that the height of jump (h), the mean power (Pmean) and the maximum power (Pmax) are statistically significant, and higher in DJ. The results prove fine adaptation of the nervous system in acrobats to muscle extension and workload, due to the 40 cm high drop jump. Presumably, this height is closest to that which acrobats experience during landing, after performing flic-flacs or round-off.