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External torque as a factor to modify load in abdominal curl-up exercises

100%
Rutkowska-Kucharska A., Szpala A.
Biomedical Human Kinetics
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2015
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vol. 7
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issue 1
EN
Study aim: the aim of our study was to evaluate electromyography (EMG) activity in exercises where the load to the muscles is determined by the external torque. In a part of the exercises, we changed the value of the external force, while in the other we modified the length of the lever arm at which the force was applied. Material and methods: the study was carried out on a group of 12 subjects (21 ± 2 years, 61 ± 4.8 mass, 172 ± 5 cm height). Electromyographic activity of the rectus abdominis (RA) muscle was evaluated by recording the EMG signal. The length of the lever arm of the external force was changed by using four different positions of the upper limbs, whereas the magnitude of the external force was changed through adding the weights of 0.5, 1.0, and 1.5 kg. The data recorded were normalized with respect to EMG activity measured under maximum voluntary contraction (MVC) conditions. Results: it was found that the change of the lever arm at which the force was applied (any change in the position of the upper limbs) causes a change in EMG activity in each part of the RA muscle from ca. 50% to ca. 100% MVC (p < 0.001). Further, the change in the external load changes statistically significantly the EMG activity only in the left upper part of the RA muscle (p < 0.05). Conclusions: activity in the RA muscle that increased for longer lever arms of the external force, offers opportunities for changing the load used during the exercise in a manner that is safe for the vertebral column.
2
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Choosing the Right Body Position for Assessing Trunk Flexors and Extensors Torque Output

81%
Szpala A., Rutkowska-Kucharska A., Drapała J., Brzostowski K.
Human Movement
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2011
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vol. 12
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issue 1
57-64
EN
Purpose. The sitting position is generally adopted when measuring the torques produced by flexors and extensors of the trunk. Results of such measurements are influenced by the strength of both abdominal muscles and flexors of the hip joint. In order to assess the effect of exercises used to strengthen the abdominal muscles it was necessary to find such a measuring position which engaged mainly the abdominal muscles. The objective of the study was an assessment of EMG activity of abdominal and spinal muscles during the measurements of muscle torques in the sitting position, as well as in the lying position. Basic procedures. Thirteen female students of the University School of Physical Education in Wrocław participated in the study. The methods of measuring muscle torques and surface electromyography (sEMG) were used under static conditions. The torques were measured on a multifunctional chair in the lying and sitting positions. The surface EMG electrodes were placed on the right and left hand sides of m. rectus abdominis (RA) and m. erector spinae (ES). Signals from both muscles were sampled at 1000 Hz. Main findings. The maximal torques of trunk flexors in the sitting position and in the lying position were similar: 130.6 ± 31.7 Nm and 129.8 ± 37.9 Nm, respectively. By contrast, the torque of trunk extensors was significantly larger when the measurement was carried out in the sitting position (228.1 ± 76.4 Nm) as compared with the lying position (148.8 ± 25.3 Nm). The ratio of the maximal torques of flexors and extensors of the trunk in the women examined was 0.572 in the sitting position and 0.872 in the lying position. Both RA and ES showed higher EMG activity in the lying position than in the sitting position. Conclusions. The higher EMG activity of the RA muscle in the lying position at the same values of the trunk flexors torque in both positions may suggest that in the sitting position flexors of the hip joint are more engaged than abdominal muscles. That is why, in order to assess the effects of abdominal muscles training, measurements of the trunk flexors torque should be performed in the lying position.
3
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The assessment of specific physical fitness of children aged 8 and 9 years participating in tennis classes using the Jindrich Hoehm test

81%
Szpala A., Rutkowska-Kucharska A., Syrewicz P.
Biomedical Human Kinetics
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2014
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vol. 6
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issue 1
EN
Study aim: The purpose of the study was to use the Jindrich Hoehm test to evaluate physical fitness in boys and girls aged 8 and 9 years participating in tennis classes. Material and methods: A total of 40 children divided into four sample groups participated in the study. The J. Hoehm test consisting of seven components was used to measure and assess the physical fitness of the research participants. This test is used in child and adolescent tennis training to assess specific physical fitness. Results: The actual data showed significant differences between 8-year-old boys and girls that were established based on the test components assessing lower extremity strength capacity and the agility assessment test. In the group of children aged 9, the differences between boys and girls emerged in the test assessing lower extremity strength capacity as well as the test component assessing the forehand and backhand footwork movement technique. Inasmuch as the test component assessing lower extremity strength capacity showed differences between 8- and 9-year-old boys, no test demonstrated statistically significant differences between 8- and 9-year-old girls. Based on the normalized data, 8-year-old girls are physically fitter than 8-year-old boys. In the group of 9-year-old children, the relation is reversed. The children participating in the study display a low level of physical fitness. Conclusion: The J. Hoehm test can be a useful tool for assessing the performance of tennis coaches.
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