Current Research in Motor Control IV

Transcription

1 Academy of Physical Education in Katowice Current Research in Motor Control IV From Theory to Implementation Editors: Grzegorz Juras, Kajetan Słomka Katowice 2012

2 KOMITET WYDAWNICZY prof. dr hab. Mirosław Ponczek, (przewodniczący), prof. dr hab. n. med. Andrzej Małecki, prof. dr hab. Sławomir Mazur, prof. dr hab. Jan Ślężyński, prof. dr hab. Janusz Iskra, dr hab. Władysław Mynarski prof. nadzw., dr hab. Rajmund Tomik prof. nadzw., dr hab. Cezary Kucio prof. nadzw., dr hab. Rafał Gnat prof. nadzw., dr Piotr Halemba, dr Jacek Polechoński Recenzent: prof. dr hab. Wiesław Osiński ISBN Copyright 2012 by AWF Katowice Projekt okładki: Kajetan Słomka Skład tekstu: BiuroTEXT Bartłomiej Szade Wydawnictwo Akademii Wychowania Fizycznego im. Jerzego Kukuczki w Katowicach Nakład 150 egz. Dystrybutor Śląska Księgarnia Kultury Fizycznej, ul. Mikołowska 72A, Katowice, ksiegarniakulturyfizycznej@wp.pl, tel

3 From Theory to Implementation 3 Contents Preface... 6 REDUCED DUAL TASK INTERFERENCE IN MULTIPLE REPEATED DUAL-TASK TESTS: AUTOMATIZATION OR TASK INTEGRATION?8 Manfred Agethen, Daniel Krause... 8 FUNCTIONAL LIMIT OF STABILITY IN RELATION TO STANDING ON INCLINED SURFACE Kristina Buckova, Zuzana Halicka, Jana Lobotkova, Frantisek Hlavacka 15 THE RELIABILITY OF FORCE PRODUCTION ERROR IN HEALTHY INDIVIDUALS Mariusz Furmanek, Kajetan Słomka, and Grzegorz Juras FINE MOTOR CONTROL AND INDICATORS OF SCHOOL READINESS 6-YEAR-OLD CHILDREN Bogusława Gierat HOW VISUAL BIOFEEDBACK MAGNIFICATION AFFECTS UPRIGHT STANCE Zuzana Halická, Jana Lobotková, Kristína Bučková, František Hlavačka 35 TEACHING METHODS IN HURDLE RACES AND RESULTS IN SPECIAL FIELD AND LABORATORY TESTS Janusz Iskra, Jarosław Gasilewski, Jolanta Hyjek, Rafał Zając, Marzena Paruzel-Dyja BUILDING SYSTEM OF FORECASTING RESULTS JUMP HEIGHT ON NEURO-FUZZY NETWORK CASCADE Ilya Y. Krivetskiy, Grigoriy I. Popov THE INFLUENCE OF PERTURBATION ON THE LIMITS OF STABILITY Patrycja Kołacz, Rafał Zając, Krzysztof Szydło, Kajetan Słomka, Grzegorz Juras COMPARISON OF MECHANICAL PARAMETERS OF THE VERTICAL JUMP WITH VARYING LOAD MUSCLES IN BASKETBALL PLAYERS Henryk Król... 63

4 4 Current Research in Motor Control IV THE COMPARATIVE ANALYSIS OF THE STANDING BACKWARD PIKED SOMERSAULT (CASE STUDY) Henryk Król, Małgorzata Klyszcz - Morciniec, Grzegorz Sobota THE INFLUENCE OF PILATES EXERCISES ON POSTURAL STABILITY OF YOUNG AND OLDER WOMEN - COMPARISON OF THE EFFECTS OF SHORT-TERM TRAINING Lidia Kuba, Artur Fredyk, Izabela Zając-Gawlak, Joanna Kantyka CHANGES IN FINE MOTOR BEHAVIOUR WITH AGE (BASED ON VISUO-PROPRIOCEPTIVE AND PROPRIOCEPTIVE ONLY FEEDBACKS) Liudmila Liutsko, Ruben Muiños and Josep Maria Tous-Ral STEP INITIATION: CHARACTERISTICS FROM ACCELEROMETRY AND CAMERA MOTION CAPTURE SYSTEM Jana Lobotkova, Zuzana Halicka, Kristina Buckova, Frantisek Hlavacka 97 PRACTICE-RELATED ADAPTATION TO MOTOR OUTPUT WITH ADDITIVE LOW-LEVEL NOISE Guo Mei-Chun, Hwang Ing-Shiou THE OWN MODIFICATION OF EXERCISE BY MEHRSHEED SINAKI AND NORDIC WALKING FOR SECONDARY PREVENTION IN OSTEOPOROSIS Agnieszka Nawrat-Szołtysik, Józef Opara, Cezary Kucio EMG SIGNAL ANALYSIS THE MVC TEST BEFORE AND AFTER FUNCTIONAL TESTING IN PATIENTS WITH GONARTHROSIS Karina Nowak, Grzegorz Sobota, Bogdan Bacik, Grzegorz Hajduk, Damian Kusz FUNCTIONAL MOVEMENT PATTERNS AND LIMITATIONS VS. PHYSICAL FITNESS PREPARATION OF 18 YEAR OLD FOOTBALLERS Marzena Paruzel Dyja, Leszek Dyja, Janusz Iskra, Jarosław Gasilewski SPORTS RESULTS IN WEIGHTLIFTING AND THEIR DETERMINANTS Anna Pilis, Krzysztof Mizera, Cezary Michalski, Jakub Jelonek, Łukasz Grela, Karol Pilis

5 From Theory to Implementation 5 THE USE OF SELECTED LINEAR MODELS IN PREDICTING THE RESULTS OF 400-METRE HURDLES RACES Krzysztof Przednowek, Janusz Iskra, Stanisław Cieszkowski TRANSLATIONAL ABILITIES OF HAND MANIPULATION IN TYPICALLY DEVELOPING SOUTH INDIAN CHILDREN D. Sangkari, Ramkumar Govindarajalu FIFTEEN MINUTE TREATMENT WITH LOW FREQUENCY, HIGH INTENSITY TRANSCUTANEOUS ELECTRICAL NERVE SIMULATION (TENS) INCREASES MAXIMUM FINGER FORCE PRODUCTION Karol Sohit and Shim Jae Kun THE INFLUENCE OF THE ADDITIONAL TASK ON POSTURAL STABILITY Krzysztof Szydło, Kajetan Słomka, Rafał Zając, Patrycja Kołacz, Grzegorz Juras CHANGES IN THE LEVEL OF STABILITY WHILE STANDING ON THE BALANCE PLATFORM ON A RIGID AND COMPLIANT SURFACE Dariusz Tchórzewski, Janusz Jaworski FITNESS ASSESSMENT IN ICE HOCKEY Milan Turek, Marek Kokinda, Róbert Kandráč HOCKEY FITNESS RELATIVE TO AGE CATEGORIES Milan Turek, Marek Kokinda, Róbert Kandráč SPECIFICITY OF LEARNING IN STABILOMETER BALANCE TASKS WITH AND WITHOUT VISION Martin Wünnemann THE RELIABILITY OF JUMPING TEST AS A TOOL FOR EVALUATION OF MOVEMENT RHYTHM Rafał Zając, Krzysztof Szydło, Patrycja Kołacz, Kajetan Słomka, Grzegorz Juras IMPACT OF EXERCISE INTENSITY ON INNER PLEXIFORM LAYER OF THE RETINA Zwierko Teresa, Lubiński W., Czepita D., Lesiakowski P., Krzepota J

6 6 Current Research in Motor Control IV Preface I believe that tradition is what matters the most. To belive is one thing, to have a chance to create a tradition is valuable. We have created our own tradition by organizing conferences on motor control in Poland. The last edition was organized from 27 to 29 September 2012 in Wisła in Beskidas Mountains. Professor Joachim Raczek, who is one of the founders of the Motor Control conference cycle, during our first meeting in 2000, said that the processes of motor control are crucial in the area of human motor activity, especially in motor rehabilitation, physical education and sport training. The meaning of this sentence justifies the aim of organizing our conferences. In my opinion, it is important to keep in mind interdisciplinary character of the motor control field but also to consider all possible data analysis and theoretical frameworks which are essential for better understanding of human motor behavior. Both, results of interesting experiments and sophisticated analysis were presented and discussed during this yearʹs conference. All participants emphasized exceptional, actual and intelligible lectures. Again, it was only possible thanks to our great Speakers! Invited lectures given by Anatol Feldman, Mark Latash, Mindy Levin, Anna Jaskólska, Slobodan Jaric, Klaus Blischke, Alexander Aruin, Normand Teasdale, Evangelos A. Christou, Marcos Duarte and Jan Celichowski were remarkable. It is worth to mention the Workshop on Motor Control that was organized just after the last edition of our conference. Here, I would like to address my special thanks to Professor Mark Latash, who was a great Lecturer. Thank You for a solid dose of knowledge, inspiration and spreading Bernstein s ghost among us! The strong will to study and investigate process of motor control is not the only incentive to organize Motor Control conferences in Poland, the second important reason is to facilitate the interaction of scientists from our part of Europe with researchers from all over the World. It is our mission to give young scientists the chance to meet, listen to and to

7 From Theory to Implementation 7 discuss with World renowned Invited Speakers. It works! The presence of a large number of young scientist not only from Poland but also from Slovakia, Czech Republic, Hungary, Germany and other countries was noticeable. I would like to warmly thank all Participants for their input to our conference! Keeping the tradition of the Motor Control series, involves the publication of the 4 th edition of Current research in motor control which is now in your hands. This collection of reviewed papers is focused on different subfields that compromise the area of motor control. Papers written by professionals from rehabilitation, sport training and clinical field were included in this volume. All of them (and a few more) were presented and discussed in late September 2012 in Wisła. Some of the papers written by Invited Speakers were published in Journal of Human Kinetics. And finally, traditionally just before or after the Olympic Games, the next Motor Control will be organized in 2016! You are welcome to participate for the first or fifth time! Tradition must go on! Grzegorz Juras

8 8 Manfred Agethen and Daniel Krause REDUCED DUAL TASK INTERFERENCE IN MULTIPLE REPEATED DUAL TASK TESTS: AUTOMATIZATION OR TASK INTEGRATION? Manfred Agethen, Daniel Krause 1 Introduction The majority of motor skills are presumably controlled with a high degree of automaticity as expertise increases. Since motor control happens unconsciously by large at this level, attention can be directed to other important aspects like for example the position of the opponent in sport games. Similar situations can be found in everyday life as well. Humans usually do not think about how to move the lower extremities when they are walking. And what is more, they can focus on other things like traffic, traffic lights or shop windows while walking. The availability of more free attentional resources over the course of practice is caused by the process of automatization (Adams 1971; Fitts, Posner 1967; Gentile 1972; Shiffrin, Schneider 1977; Logan 1988; Keele et al. 2003). A gradual shift of motor representation from declarative to nondeclarative memory structures leads to more automatic motor control (Blischke 2000) which goes hand in hand with shifts of neuronal activity (Doyon et al. 2009). As a measure for automaticity many studies used cognitive secondary tasks (Blischke 2000; Ruthruff, Van Selst, Johnston, Remington 2006). During simultaneous conduction of a motor and a cognitive task, there should be no or reduced interferences when performing a motor task with a high degree of automaticity. This is where a synchronous strain using a cognitive secondary task, which needs attention, can expose in how far the primary task still needs conscious control. There 1 - University of Paderborn, Paderborn, Germany

9 Reduced Dual Task Interference in Multiple Repeated Dual-Task Tests: 9 fore, interferences on the working memory level can be assumed, whenever there are influences on performance compared to single task assignments (Abernethy 2001). When defining a secondary task and the consumed resources according to Baddeley s working memory model (2002), we expect higher interference, if the tasks consume the same working memory resources. And what is more, the Parallel Neural Network Model (Hikosaka, Nakamura, Sakai, Nakahara 1999) implies that control of movement sequences in early learning stages is based on an attention dependent visual spatial code, while less attention dependent motor code gets more important in later stages. In order to receive valid answers to the question if and to what extent the primary task still needs attentional resources, the secondary task should include similar requirements for the working memory. Following these ideas we assume that a visual spatial secondary task seems especially feasible for spatial movement sequences, because it causes a high interference on resource levels for non automatized movements by straining the visual spatial sketchpad (Baddeley 2002). One important methodological problem of testing automaticity by dual task tests derives from findings that are indicative of other explanations for the reduction of dual task costs apart from the expected automatization of motor control. Some studies show an effective task integration of the two tasks (effective switching of attention between the tasks) instead of an automatization of the primary task to reduce dual task costs (Blischke, Wagner, Zehren, Brückner 2010). Extensive practice of a task pair can lead to different effects. On the one hand it can promote automatization of individual tasks, which is characterized by reduced attentional demands in motor control and on the other hand it can teach participants to efficiently integrate processing of a specific task pair (Ruthruff et al. 2006). The reduction of dual task costs caused by automatization of the primary task is not related to the dual task context. Therefore, also in dual task contexts, which have not been practiced before (primary task + transfer secondary task) reduced DTC should be apparent. Several repetitions of the test could also lead to integrated processing of the task caused by frequent performance of the dual task context. As a conclusion, another

10 10 Manfred Agethen and Daniel Krause transfer task should be conducted to reliably exclude task integration processes as the explanatory approach. If dual task tests are multiple repeated, as it is the case in many experimental studies (e.g. Poldrack et al. 2005), the resulting reduction of dual task costs (DTC) can be caused by different mechanisms; automatization or task integration. The present study provides insides to the validity of multiple repeated dual task tests to monitor task automatization. The transfer test design should differentiate between efficiently integrated performances of a task pair as a consequence of multiple repeated dual task tests and automatization of an individual task as a consequence of extensive motor skill practice between the tests. Methods 10 subjects (age: 26.9 [SD = 3.8] years; 4 female and 6 male) gave a written informed consent. They practiced an elbow extension flexion sequence with three movement reversals at 80, 20 and 70 measured from a defined starting position of an arm lever device with a potentiometer. They should perform the task as precise and as fast as possible. The 460 practice trials were distributed over 6 sessions (see table 1). To support motor skill automatization processes the participants practiced with an attention distracting secondary task (spatial workingmemory updating task) which was not used in the dual task tests (for the effects of dual task practice on automatization see Blischke 2000). Table 1 Tests and practice blocks of the 7 experimental sessions Feedback for movement reversals and time was provided after every second trial. In pretests, at the beginning of each session and in one re

11 Reduced Dual Task Interference in Multiple Repeated Dual-Task Tests: 11 tention test, the movement task and a visual spatial 2 back task (onset interval: 1000ms; stimulus duration: 500ms) were tested under singleand dual task conditions (6 trials each). The tests were ordered beginning with 3 single task trials of the cognitive task, followed by 3 trails singletask trials of the motor task, 6 dual task trials, additional 3 single task trials of the motor task and additional 3 single task trials of the cognitive task. Priority was instructed for the 2 back task (multiple repeated). For testing context unspecific DTC reduction, a transfer dual task test (singlerepeated: pretest and retention) with a visual spatial Sternberg task (onset interval: 900ms; stimulus duration: 450ms) was conducted. The responses of the cognitive tasks (2 back events and Sternberg targets) were collected via the space button of a standard PC keyboard. Results The results indicate a context specific reduction of DTC. The 2 (test: pretest; retention) x 2 (cognitive load: single task; dual task) ANOVA Fig. 1 Means and standard deviations for single (ST) and dual task (DT) performance in pretest and retention for the multiple repeated 2 back test (left) and the singlerepeated Sternberg test (right) shows a significant interaction effect for the multiple repeated 2 back test, F(1, 9) = 13.85; p =.010; eta² =.61. The errors for the 2 back test de

12 12 Manfred Agethen and Daniel Krause creases from pretest to retention in the dual task conditions, t(9) = 4.74; p= 001; d = 1.53, while this is not the case for the single task condition, t(9) = 1.43; p =.186; d = 0.45 (Fig. 1 on the left). The respective ANOVA for the single repeated Sternberg test shows no significant interaction, F(1,9) < 0.01; p >.999; eta² <.01 (Fig. 1 on the right). Analyzing the absolute error, neither the ANOVA for the n back test, F(1, 9) = 1.41; p >.530; eta² =.14, nor the ANOVA for the Sternberg test, F(1, 9) = 2.41; p =.310; eta² =.21, show significant interactions test x cognitive load. Discussion The results show distinct DTC reduction for the multiple repeated 2 back test but not for the single repeated Sternberg test. This indicates a context specific DTC reduction. Automatization as a consequence of extensive motor skill practice allows participants to perform tasks without limited central resources and thus the reduction of DTC should be context independent and should occur in the single repeated Sternberg test as well. Contrary to this prediction, we observed no DTC reduction for the Sternberg test. Alternatively to task automatization, the multiple repetition of the dual task context in the repeated 2 back test might allow an efficient integration of the two tasks. For instance, repeated dual task trials might allow participants to re organize two tasks into a single super task or optimized task switching processes, thus eliminating resource competition (Ruthruff et al. 2006). According to this task integration hypothesis, integration requires dual task practice, which could be given in the 36 repetitions of the specific dual task context (arm movement and 2 back task). Therefore reduced dual task interference in multiple repeated dualtask tests should be considered with caution if automaticity is the construct of interest. While statistical data for the group seem to prove task integration instead of automatization, looking at individuals offers a more heterogeneous picture. The results of 3 participants seem to indicate that some individuals did not adopt a task integration strategy. Furthermore they show

13 Reduced Dual Task Interference in Multiple Repeated Dual-Task Tests: 13 a DTC reduction in both tests (2 back + Sternberg). This might be an indication for automatization for these particular individuals. Compliance to the prioritization of the motor task seemed to be low, as can be assumed from the behavioral data. Maybe movement intrinsic error feedback directed attention to the movement. References Abernethy, B. Attention. In R. N. Singer (Ed.), Handbook of Sport Psychology. Second Edition New York: Wiley & Sons, Pp Abernethy, B. Dual Task methodology and motor skill research. Some Applications and Methodological Constraints. Journal of Human Movement Science, 14, , Adams, A.J. A closed loop theory of motor learning. Journal of Motor Behavior, 3, , Baddeley A.D. Is working memory still working? American Psychologist, 56, , Blischke, K. Two procedures one mechanism? Recent findings on the automation of voluntary movements. Journal of Human Kinetics, 4, 3 16, Blischke, K., Wagner, F., Zehren, B., Brückner, S. Dual task practice of temporally structured movement sequences augments integrated task processing but not automatization. Journal of Human Kinetics, 25, 5 15, Doyon, J., Bellec, P., Amsel, R., Penhune, V., Monchi, O., Carrier, J., et al. Contributions of the basal ganglia and functionally related brain structures to motor learning. Behavioral Brain Research, 199, 61 75, Fitts, P.M., Posner, M.I. Human Performance. Belmont: Brooks/Cole, 1967 Gentile, A.M. A working model of skill acquisition with application to teaching. Quest, 17, 3 23, Hikosaka, O., Nakahara, H., Rand, M.K., Sakai, K., Lu, X., Nakamura, K., Miyachi, S., Doya, K. Parallel neural networks for learning sequential procedures. Trends in Neurosciences, 22, , Keele, S.W., Ivry, R., Mayr, U., Hazeltine, E., Heuer, H. The cognitive and neural architecture of sequence representation. Psychological Review, 110, , 2003.

14 14 Manfred Agethen and Daniel Krause Poldrack, R. A., Sabb, F. W., Foerde, K., Tom, S.M., Asarnow, R. F., Bookheimer, S. Y., Knowlton, B. J. The neural correlates of motor skill automaticity. Journal of Neurophysiology, 25, , Ruthruff, E., Van Selst, M., Johnston J. C., Remington, R. How does practice reduce dual task interference: integration, automatization, or just stageshortening? Psychological Research, 70, , Schneider, W., Shiffrin, R. M. Controlled and automatic human information processing: I. Detection, search and attention. Psychological Review, 84, 1 66, 1977.

15 Functional limit of stability in relation to standing on inclined surface 15 FUNCTIONAL LIMIT OF STABILITY IN RELATION TO STANDING ON INCLINED SURFACE Kristina Buckova, Zuzana Halicka, Jana Lobotkova, Frantisek Hlavacka 1 Introduction The ability to move the center of gravity voluntarily and keep balance is fundamental for performing mobility tasks such as reaching for objects, transitioning from a seated to standing position or walking. The maximum displacement of the center of body mass to external postural perturbations that can be controlled with or without a fall or a step is defined as limit of stability (Horak et al., 2005). To investigate limits of stability (LOS) in absence of external perturbation, the maximum voluntary inclined posture can be evaluated (Schieppati et al., 1994). It is known that limitations in LOS is related to risk for fall or instability during postural activities and gait. The aim of this study was to investigate the effect of different support surface slope angle on limit of stability in forward direction. Methods In the study participated 8 young volunteers (2 male, mean age 26.1 ± 0.9 years, mean height ± 1.2 cm, mean weight 62.7 ± 3.1 kg) free of any neurological or musculoskeletal disorders. All subjects gave in 1 - Slovak Academy of Sciences, Laboratory of Motor Control, Institute of Normal and Pathological Physiology, Bratislava, Slovakia

16 16 Kristina Buckova et al. formed consent prior to participation and the local Science Ethical Committee approved the experimental protocol. The subjects stood on support surface with variable slope angle which was placed on force platform equipped with automatic weight correction and with direct output of center of pressure (CoP) signal. CoP data in anterior posterior direction were sampled at 100Hz and recorded on PC. Three dual axis accelerometers (ADXL203) were placed on the fifth lumbar (L5), the fourth thoracic (Th4) vertebra and on half way of ischial tuberosity and popliteal crease on the posterior aspect of the right thigh (RT). Sensors measured both dynamic and static acceleration with a fullscale range of ±1.7 g. The acceleration output was low pass filtered with cut off frequency of 5 Hz and was calibrated in stationary conditions as inclinometer for ± 30 degrees range of body tilt. Participants were instructed to maintain an upright standing position, with arms comfortable crossed on the chest and with feet parallel at their comfortable stance width. Initial stance position was consistent from trial to trial. After hearing sound signal (second sec after trial start) subjects were asked to lean as far as they could at their comfortable speed without lifting heels of flexing their hips (using ankle strategy) and persist in this position till to trial end. The slope angle of support surface was at first in horizontal position with 0 (S0), afterwards in 10 (S1) and 20 (S2) slope angle position. The measurements in these 3 conditions were done with eyes open and eyes closed. Each trial lasted 10s and was repeated 3 times. We evaluated the mean displacement of CoP position and the mean of angle of body segment tilts in forward direction measured by accelerometers during interval 6 10s of the each trial. Data were evaluated with MATLAB programs. Analysis of variance with 2 way repeated measures was used as a statistic method. Post hoc pairwise comparisons with LSD adjustment were performed. Results Maximal voluntary body tilt during stance on inclined support surface was related to slope angle of surface. With increasing angle of sur

17 Functional limit of stability in relation to standing on inclined surface 17 face inclination, the displacement of the CoP during maximal body tilt was decreased (Fig.1). Similar time courses were found during body tilts with eyes closed, with decreased values of maximal CoP excursion (Fig.2A). Statistical analysis showed that CoP displacement during body tilt with eyes open on horizontal support surface in comparison to first platform inclination (S0 S1) level was significant (p<0.05). Also comparison to second platform inclination (S0 S2) level was significant (p<0.01). The difference between S1 and S2 was not significant (Fig. 2A). Data from inclinometer placed at RT showed (Fig.2B) that the stabilized leaning of this segment was smaller in situations with increased surface slope (p<0.01). Data from L5 inclinometer similarly showed (Fig. 2C) significant effect of support surface angle slope on body lean (p<0.01). No significant results were between horizontal support surface and S1 or S2 data from Th4 inclinometer (Fig.2D). We also found out a significant influence of vision on amplitude in CoP and RT (p 0.01) and L5 (p 0.05). From Th4 data a significant effect of vision was not improved. Interaction between vision and support surface slope angle was also not occurred. [cm] 4s 10 CoP forward 5 S0 platform horizontal 0 S1 platform slope angle10 S2 platform slope angle 20 0 sound signal time [s] Fig. 1 The grouped averages of CoP forward displacements in 3 angle slope levels (S0, S1, S2) of support surface in condition with eyes open. Estimated values represented an averages of stabilized forward leaning (last 4 s of the trial). 9 10

18 18 Kristina Buckova et al. [cm] A * CoP ** EO EC [o] B 10 8 RT ** ** ** ** 4 2 * 0 C S0 S1 S2 L5 0 D S0 S1 S2 Th4 [o] 10 8 ** [o] ** ** * * 0 0 S0 S1 S2 S0 S1 S2 Fig. 2 Functional limit of stability presented by CoP displacement and three inclinometers outputs (mean values ± S.E.M.). ** p<0.01, * p<0.05. Black line eyes open, gray line eyes closed. Discussion Support surfaces inclined from horizontal plane represent a common challenge in daily postural activities of human. An example should be also women s walking in high heels shoes. In this work we focused on effect of inclined support surface on magnitude of voluntary body tilt, by which is characterized functional limit of stability. Our results showed that functional limit of stability in forward direction is reduced with increasing of support surface angle slope.

19 Functional limit of stability in relation to standing on inclined surface 19 If the body is modelled as an inverted pendulum, CoP adjustments can provide insight into how the CNS controlling COM movement (Winter et al., 1990). One of the goals of CNS is to control movement of the COM within the base of support. If we consider an increase of support surface slope angle as progressive increases in postural threat, it may induce tighter control of posture to decrease the possibility of the COM falling outside of the base support. Thus, the CoM can be regulated within a smaller boundary by reducing the amplitude of CoP displacement. (Adkin et al., 2000). Whole body tilt measured by CoP displacement and body segment tilts measured by inclinometers at L5 and RT levels showed the similar and significant results related to angle of inclined support surface (Fig. 2A,B,C). Inclination of upper trunk at Th4 level were not significant. Because our subjects were instructed to tilt forward without flexion/extension of knee or hip using only ankle strategy, likely in condition S1 they used combined ankle and hip strategy with flexed trunk. From these results we can conclude that balance stability is reduced during standing and walking on inclined support surface. References Adkin A. L., Frank J. S., Carpenter M. G., Peysar G. W. Postural control is scaled to level of postural threat. Gait and Posture. 12: 87 93, Horak F.B., Dimitrova D., Nutt J. Direction specific postural instability in subjects with Parkinson s disease. Exp. Neurol. 193: , 2005 Schieppati M., Hugon M., Grasso M., Nardone A, Galante M. The limits of equilibrium in young and elderly normal subjects and in Parkinsonians. Electroencephalog. Clin. Neurophysiol. 93: , 1994 Winter D. A., Patla A. E., Frank J.S. Assesment of balance control in humans. Med. Prog. Technol. 16: 31 51, 1990 Acknowledgments This work was supported by VEGA grants No. 2/0186/10 and 1/0070/11.

20 20 Mariusz Furmanek et al. THE RELIABILITY OF FORCE PRODUCTION ERROR IN HEALTHY INDIVIDUALS Mariusz Furmanek, Kajetan Słomka, and Grzegorz Juras 1 Introduction Proprioception is described as afferent information arising from internal peripheral areas of the body that contribute to postural control, joint stability, and several conscious sensations (Riemann, Lephart 2002). Therefore, human conscious proprioceptive sense (PS) can be considered as a subset of somatosensory system. Joint position sense, kinesthesia and sense of force (resistance or heaviness) all comprise PS. There are three major testing procedures for PS: (1) reproduction of passive/active positioning commonly called as JPS (Fridén et al. 2001, Grob et al. 2002, Juul Kristensen et al. 2008), (2) threshold to detection of passive motion TTDPM (Barrack et al. 1989, Ageberg et al. 2007, Boerboom et al. 2008, and (3) force production sense FP (Dover, Powers 2003). The last one is studied the least, despite that it provides crucial information regarding proprioception system. The force production tests involve ability of subjects to differentiate between levels of muscle force (Raczek et al. 2002, Pincivero et al. 2000, Docherty, Arnold 2008, Lauzière et al. 2012). In order to assess FP a reference force is used; it is usually defined as a percentage (e.g. 10, 20, 25, 30, 40, 50, 75, 80, and 90%) of a maximal isometric voluntary contraction (MIVC), which is determined first. In the FP test an attempt is made to replicate the required level of the reference force. Testing can include several movement tasks such as; bilateral force matching task (Carson et 1 - The Jerzy Kukuczka Academy of Physical Education, Department of Human Motor Behaviour, Katowice, Poland