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Isokinetic Strength Profile of Elite Female Handball Players

100%
Xaverova Z., Dirnberger J., Lehnert M., Belka J., Wagner H., Orechovska K.
Journal of Human Kinetics
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2015
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vol. 49
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issue 1
257-266
EN
Systematic assessment of muscle strength of the lower extremities throughout the annual training cycle in athletes is crucial from a performance perspective for the optimization of the training process, as well as a health perspective with regard to injury prevention. The main aim of the present study was to determine isokinetic muscle strength of the knee flexors and extensors in female handball players at the beginning of a preparatory period and to assess whether there were any differences between players of different performance levels. The performance level was expressed by means of membership of the Women’s Junior National Handball Team (JNT, n=8) or the Women’s National Handball Team (NT, n=9). The isokinetic peak torque during concentric and eccentric single-joint knee flexion and extension was measured at angular velocities of 60, 180, 240°/s (concentric) and 60°/s (eccentric). The Mann- Whitney test showed no significant differences in the peak torques or ipsilateral ratios between the two groups. The bilateral force deficit (BFD) for concentric extension at 240°/s was significantly higher in the JNT compared with the NT (p=0.04; d=1.02). However, the results of individual evaluation show that the BFD was more frequent in the NT in most measurements. A high BFD was evident in the eccentric mode in both groups highlighting a need for particular strengthening. With regard to low strength ratios a prevention programme should be suggested for both observed groups of professional female handball players to reduce the risk of injury.
2
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Choosing the Right Body Position for Assessing Trunk Flexors and Extensors Torque Output

100%
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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Maximal Isokinetic Peak Torque and EMG Activity Determined by Shorter Ranges of Motion

88%
Oliveira A., Corvino R., Gonçalves M., Caputo F., Denadai B.
Human Movement
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2012
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vol. 13
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issue 2
102-108
EN
Purpose. Isokinetic tests are often applied to assess muscular strength and EMG activity, however the specific ranges of motion used in testing (fully flexed or extended positions) might be constrictive and/or be painful for patients with injuries or under-going rehabilitation. The aim of this study was to examine the effects of different ranges of motion (RoM) when determining maximal EMG during isokinetic knee flexion and extension with different types of contractions and velocities. Methods. Eighteen males had EMG activity recorded on the vastus lateralis, vastus medialis, semitendinosus and biceps femoris muscles during five maximal isokinetic concentric and eccentric contractions for the knee flexors and extensors at 60° · s-1 and 180° · s-1. The root mean square of EMG was calculated at three different ranges of motion: (1) a full range of motion (90°-20° [0° = full knee extension]); (2) a range of motion of 20° (between 60°-80° and 40°-60° for knee extension and flexion, respectively) and (3) at a 10° interval around the angle where peak torque is produced. EMG measurements were statistically analyzed (ANOVA) to test for the range of motion, contraction velocity and contraction speed effects. Coefficients of variation and Pearson's correlation coefficients were also calculated among the ranges of motion. Results. Predominantly similar (p > 0.05) and well-correlated EMG results (r > 0.7, p ≤ 0.001) were found among the ranges of motion. However, a lower coefficient of variation was found for the full range of motion, while the 10° interval around peak torque at 180° · s-1 had the highest coefficient, regardless of the type of contraction. Conclusions. Shorter ranges of motion at around the peak torque angle provides a reliable indicator when recording EMG activity during maximal isokinetic parameters. It may provide a safer alternative when testing patients with injuries or undergoing rehabilitation.
4
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Changes in Muscle Strength in U19 Soccer Players During an Annual Training Cycle

88%
Lehnert M., Xaverová Z., Croix M. D. S.
Journal of Human Kinetics
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2014
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vol. 42
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issue 1
175-185
EN
The aim of the study was to investigate the seasonal variation in isokinetic strength of the knee flexors and extensors, and conventional (H/QCONV) and functional (H/QFUNC) hamstring to quadriceps strength ratios in highly trained adolescent soccer players. The players (n=11; age 17.8±0.3) were measured at the end of the competitive season (autumn), at the beginning and the end of pre-season (winter) and during the sixth week of a new competitive season. Isokinetic peak torque (concentric and eccentric) was measured at 60°•s-1 in a sitting position with the hip flexed at 100°. The testing range of motion was set from 10 - 90° of knee flexion. The players performed a set of five maximum repetitions for both the dominant and non-dominant leg. Statistically significant differences (p<0.001) between the four seasonal measurements were noted for peak torque of the dominant leg knee flexors in concentric muscle action only. A post hoc analysis revealed a statistically significant increase in peak torque from the 1st to the 4th measurement (p<0.001; d=0.692) and from the 2nd to the 4th (p<0.01; d=0.564). The differences in the changes of peak torque of the knee flexors and extensors depending on type of muscle action and tendencies found in the H/Q ratios throughout the annual training cycle indicate that strength assessment of the knee flexors and extensors and their balance throughout the annual training cycle could be beneficial for elite male adolescent soccer players both in terms of performance and risk of injury.
5
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Induction motor analysis employing optimal torque predictor and massive conductor approach

88%
Bernat J., Stępień S.
Archives of Electrical Engineering
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2010
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vol. 59
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issue 1
6
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Buckling of moderately thick annular plates subjected to torque

71%
Bagheri H., Kiani Y., Eslami M. R., Bagheri H., Kiani Y., Eslami M. R.
Archive of Mechanical Engineering
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2019
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vol. 66
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issue 2
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