Wyniki wyszukiwania - BazTech

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Measurement of maximal isometric torque and muscle fatigue index of the knee muscles in male athletes

Danek Janusz, Wojtasik Wojciech, Szulc Adam

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 3

31--37

EN

The aim of the paper was to analyse variables related to the force and fatigue of knee muscles in the right and left lower limbs among 17 male athletes. Methods: For both muscle groups, maximal isometric torque (Fmax) was determined with the use of Biodex System 4 Pro and the values of muscle fatigue index (FATI1–3) were calculated. Results: A significant difference was observed between the groups of short- and long-distance runners in the values of all fatigue indices of knee joint extensor muscles in the right limb. In turn, between the groups of athletes who had trained for 2–4 years or for 4.5–7 years and the group who had trained for 7.5–13 years, significant differences were observed in the values of all fatigue indices of knee joint flexor muscles in the right limb. The group training for 3–12 hours per week and the group training for 12.5–18.0 hours per week in the sports club differed significantly in the value of the maximal isometric torque of knee joint flexor muscles in the right limb and in the values of some fatigue indices (FAT1, FAT3) for knee joint flexor muscles in the right limb. The study reported numerous positive correlations between the assumed characteristics and the investigated variables of knee joint extensor and flexor muscles in the right and left lower limbs. Conclusions: Athletes present certain changes in variable values and positive correlations between some characteristics and investigated variables of selected knee muscles.

2

Concurrent validity and reliability of proprietary and open-source jump mat systems for the assessment of vertical jumps in sport sciences

Pueo B., Jimeney-Olmedo J. M., Lipińska P., Buśko K., Penichet-Tomas A.

Acta of Bioengineering and Biomechanics

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2018

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Vol. 20, no. 3

51--57

EN

Vertical jump tests are used to assess lower-limb power of athletes in sport sciences. Flight time measurement with jump-mat systems is the most common procedure for this purpose. The aim of this study was to analyze the concurrent validity and reliability of two proprietary systems (Globus and Axon) and an open-source system (Chronojump). Methods: A conditioning electric circuit governed by a controlled wave generator is designed to substitute athletes jumping on a physical mat. In order to look for possible differences associated to timekeeping by each microcontroller device, all three systems are fed by the circuit simultaneously. Results: Concurrent validity was high for the three systems. Standarized typical error of estimate (TEE) was trivial, according to MBI interpretation, as well as perfect Pearson correlation coefficient. Reliability was assessed using coefficient of variation of flight time measure, resulting in 0.17–0.63% (0.05–0.12 cm) for Globus, 0.01% (0.09 cm) for Chronojump and 5.65–9.38% (2.15–3.53 cm) for Axon. These results show that all jump-mat system produced nearly identical measures of flight time so they can be considered valid and reliable for practical purposes. In comparison, Chronojump showed the best performance whereas Axon showed enough variability and disagreement to pose a problem in testing elite athletes. Conclusions: These experiments show that open-source jump mats are as valid and reliable as their proprietary counterparts at a lower cost. Therefore, practitioners can be confident in using Globus or Chronojump systems to test athletes’ jump height because of their negligible errors and Axon system to monitor general population.

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Relationship between lower limbs kinematic variables and effectiveness of sprint during maximum velocity phase

Struzik A., Konieczny G., Grzesik K., Stawarz M., Winiarski S., Rokita A.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 4

131--138

EN

Purpose: The aim of the study was to determine the relationships between time of running over a 15–25 m section of a 30-meter run along a straight line and changes in the angle and angular velocity observed in ankle, knee and hip joints. Therefore, the authors attempted to answer the question of whether a technique of lower limbs movement during the phase of sprint maximum velocity significantly correlates with the time of running over this section. Methods: A group of 14 young people from the Lower Silesia Voivodeship Team participated in the experiment. A Fusion Smart Speed System was employed for running time measurements. The kinematic data were recorded using Noraxon MyoMotion system. Results: There were observed statistically significant relationships between sprint time over a section from 15 to 25 m and left hip rotation (positive) and between this time and left and right ankle joint dorsi-plantar flexion (negative). Conclusions: During the maximum velocity phase of a 30 m sprint, the effect of dorsi-plantar flexion performed in the whole range of motion was found to be beneficial. This can be attributed to the use of elastic energy released in the stride cycle. Further, hip rotation should be minimized, which makes the stride aligned more along a line of running (a straight line) instead of from side to side.

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Leg stiffness during phases of countermovement and take-off in vertical jump

Struzik A., Zawadzki J.

Acta of Bioengineering and Biomechanics

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2013

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Vol. 15, no. 2

113--118

EN

With respect to cyclic movements such as human gait, running or hopping, leg stiffness is a little variable parameter. The aim of this study was to investigate changes in leg stiffness during the phase of countermovement and take-off when performing a single maximum counter-movement jump. Kistler force plates and a BTS SMART system for comprehensive motion analysis were employed in the study. The study covered a group of 12 athletes from university basketball teams. Leg stiffness was calculated in those parts of countermovement and take-off phases where its level is relatively constant and the relationship F(Δl) is similar to linear one. Mean total stiffness (±SD) in both legs in the countermovement phase amounted to 6.5 ± 1.5 kN/m, whereas during the take-off phase this value was 6.9 ± 1 kN/m. No statistically significant differences were found between leg stiffness during the countermovement phase and takeoff phase in the study group at the level of significance set at α = 0.05. This suggests that the leg stiffness in phase of countermovement and phase of take-off are much similar to each other, despite different function of both phases. Similar to cyclic movements, leg stiffness turned out relatively constant when performing a single vertical jump. There are also reported statistically significant correlations between body mass, body height, length of lower limbs and leg stiffness. The stiffness analysed by the authors should be understood as quasi-stiffness because the measurements of ΔF(Δl) were made during transient states where inertia and dumping forces are likely to affect the final result.