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Anticipatory Postural Adjustments in Dart Throwing

100%
Juras G., Słomka K.
Journal of Human Kinetics
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2013
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vol. 37
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issue 1
39-45
EN
The aim of this study was to explore the effects of accuracy constraints on the characteristics of anticipatory postural adjustments (APA) in a task that involves a movement consisting of a controlled phase and a ballistic phase. It was hypothesized that APA scaling with task parameters (target size) would be preserved even when the task is performed by muscles that have no direct effects on APA. Sixteen healthy right handed subjects participated in the study. All participants had no prior experience in dart throwing. Subjects’ average age was 24.1 ± 1.9 years. A force platform and a motion capture system were used to register kinetics of the body and kinematics of the throwing arm and throwing accuracy. The experiment consisted of six series of twenty consecutive dart throws to a specified target. Target sizes (T2-T6) were set at 25%, 50%, 75%, 125% and 150% of target 1 (T1) initially set as the spread of the last 20 throws in a 50 throw training session. This allowed to distinguish six indexes of difficulty (ID’s) ranging from 2,9 to 5,9. A one-way ANOVA for repeated measures was used for statistical analysis. Results of ANOVA showed a significant effect of target size at Constant Error but no effect at APA time. There were also no significant differences between hit and miss throws. From a control perspective, it can be stated that changes in central commands did not lead to changes in APA time in the analyzed motor task.
2
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Evaluation of the Limits of Stability (LOS) Balance Test

71%
Juras G., Słomka K., Fredyk A., Sobota G., Bacik B.
Journal of Human Kinetics
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2008
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vol. 19
39-52
EN
The main objective of this study was the estimation of intrasession reliability of the limits of stability (LOS) test conducted on a force platform as an alternative measurement to standard posturography in quiet standing. Fifteen healthy adults took part in the experiment. The standardized measurement protocol of the LOS test was proposed. It consists of three phases - 1st phase - 10s of quiet standing, 2nd phase - the maximal forward leaning in a self paced manner, and 3rd phase - maintenance of maximal forward leaning position. The analysis of variance Friedman's ANOVA and Repeated Measures ANOVA/MANOVA was used to diagnose the differences between 10 consecutive trials of the LOS test. In order to establish reliability of the test, the intraclass correlation (ICC) procedure was used. We presented different ways of maximal center of pressure (COP) excursion estimates. The results of this study show no significant differences between the chosen parameters of the LOS test. Moreover, the measurement of the range of COP excursion, which is most commonly analyzed in such tests, showed to be quite reliable with ICC2,1 above .85. LOS test conducted along the standard procedure should be considered as a very useful method in clinical and research conditions. Still the specific parameters of the LOS test should be given more thorough insight, but it is a very good alternative to quiet standing posturography.
3
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Subjective vs objective evaluation of knee stability in patients before and after anterior cruciate ligament reconstruction

71%
Wysota A., Pawlak D., Ficek K., Ficek J., Juras G.
Central European Journal of Sport Sciences and Medicine
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2014
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vol. 6
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issue 2
59-66
EN
Every year, the number of anterior cruciate ligament ruptures increases considerably. The present analysis compares patients’ subjective sensations after the ACL injury to an objective arthrometric examination. The subjective evaluation of the knee-joint condition was performed using the Lysholm score scale and IKDC 2000 scale, whereas the objective evaluation was performed using a GNRB device to obtain an arthrometric measurement. Both measurement methods were performed before ACL reconstruction and after the rehabilitation process of ±11.5 months. The following research was conducted on a group of 8 patients who underwent anterior cruciate ligament reconstruction. Statistical analysis did not reveal any significant differences between the arthrometric examination and the subjective score scales. The test indicated the significant differences between the score scales questionnaires completed before and after the surgery. The conclusions that can be drawn from the present analysis show us the importance of using subjective evaluation devices. Despite the lack of significance in the examination performed with the objective device, the self-evaluation of knee-joint efficiency made by the patient indicated a significant improvement.
4
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Knee joint position sense in physically active patients after ACL reconstruction

71%
Pawlak D., Wysota A., Furmanek M., Ficek K., Juras G.
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EN
The term “proprioception” is defined as the conduction of sensory information deriving from proprioceptors that have an impact on conscious sensations, posture and trans-segmental sense. An ACL injury may lead to functional knee joint instability. According to research, this may result in impaired movement sensation and joint position. The purpose of this study was to evaluate the joint position sense (JPS) in patients before arthroscopic ACL reconstruction and 5 months after the surgery. The examinations were conducted in a group of twelve specifically selected male patients. The examination procedure consisted of JPS measurement in both lower limbs (the operated and the healthy one) during active extension in a range of angles: 30, 45, 60°. The level of significance was: p < 0.05. The analysis of variance performed for repeated measurements (ANOVA) did not indicate any statistically significant differences of JPS in comparisons made between the operated and the healthy limb. Statistical values for the absolute, relative, and variable errors were p = 0.7684, p = 0.1546, p = 0.5694 respectively. The obtained results do not indicate any limitation of proprioception in patients with ACL injury before the intervention or half a year later.
5
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The Effect of a Single Session of Whole-Body Vibration Training in Recreationally Active Men on the Excitability of the Central and Peripheral Nervous System

61%
Chmielewska D., Piecha M., Blaszczak E., Król P., Smykla A., Juras G.
Journal of Human Kinetics
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2014
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vol. 41
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issue 1
89-98
EN
Vibration training has become a popular method used in professional sports and recreation. In this study, we examined the effect of whole-body vibration training on the central nervous system and muscle excitability in a group of 28 active men. Subjects were assigned randomly to one of two experimental groups with different variables of vibrations. The chronaximetry method was used to evaluate the effect of a single session of whole-body vibration training on the excitability of the rectus femoris and brachioradialis muscles. The examination of the fusing and flickering frequencies of the light stimulus was performed. An increase in the excitability of the quadriceps femoris muscle due to low intensity vibrations (20 Hz frequency, 2 mm amplitude) was noted, and a return to the initial values was observed 30 min after the application of vibration. High intensity vibrations (60 Hz frequency, 4 mm amplitude) caused elongations of the chronaxy time; however, these differences were not statistically significant. Neither a low intensity vibration amplitude of 2 mm (frequency of 20 Hz) nor a high intensity vibration amplitude of 4 mm (frequency of 60 Hz) caused a change in the excitability of the central nervous system, as revealed by the average frequency of the fusing and flickering of the light stimulus. A single session of high intensity whole-body vibration did not significantly decrease the excitability of the peripheral nervous system while the central nervous system did not seem to be affected.
6
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Intra-Personal and Inter-Personal Kinetic Synergies During Jumping

61%
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.
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