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Effect of deep brain stimulation on a rapid arm movement in Parkinson's disease
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Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
hypothesized that a standardized fitting technique could be used to ascertain important values (e.g., H-threshold, 50% Hmax, Hmax) for comparison and provide a reliable tool for researchers to analyze the H-reflex RC. The M-wave was fit using a sigmoid curve based on a logistic equation to mimic the physiologically-based predicted response to varying stimulus intensity. The optimal fit of the sigmoid curve to the M-wave was evaluated using a nonlinear least squares iterative fit to the M-wave data to provide the best values of both R 2 and RMSE. Due to the variable nature of the H-reflex RC, both the M and the H-wave were fit using a smoothing-spline interpolant. This method is relatively insensitive to the spacing of intensities and the variability in the data. The reliability of the fitted RC was tested by comparing the fitted data to the average H-reflex and M-wave data obtained from an experimental trial in which the stimulus intensity was held constant. The amplitude of the H- and M-responses taken from the constant intensity trials were 5 0 ± 16% Mmax 5 ± 3 % Mmax, respectively. The smoothing spline fitted data corresponding to the constant intensity value yielded an H-reflex amplitude of 49 ± 16% Mmax and an M-wave of 4 ± 4 % Mmax. The value obtained from the sigmoid curve fit to the M-wave was 7 ± 12% Mmax. Thus, these RC curve fitting techniques could provide a valuable analysis tool in H-reflex studies. Supported by NSERC. 4376 We-Th, no. 37 (P56) Effect of different movement patterns on functional reach C.-R Liao, S.-I. Lin. Department of Physical Therapy, National Cheng Kung
University, Tainan, Taiwan Background and Purpose: Functional reach test (FRT) is frequently used to measure dynamic standing balance. It is not clear if reach strategy would affect the association between reach distance and dynamic balance ability. The purposes of this study were to investigate the extent to which reach distance reflected dynamic balance and the contribution of movement kinematics to reach performance. Methods: Twenty-two young adults performed FRT involving standing with the feet shoulder width apart, raising one arm 900 , and then reaching forward as far as possible without moving the feet or losing balance. A 6-camera VICON motion system was used to record the body kinematics. A hip strategy (HIP-S) was defined as having the ankle move in the plantarflexing direction during reaching. An ankle strategy (ANKLE-S) was defined as beginning reaching with ankle dorsiflexion and with total hip flexion range smaller than 15 °. The variables of interest were reach distance, range of center of mass (COM) forward displacement, range of trunk, hip, and ankle angular displacement, and hip-trunk ratio (ratio between trunk and hip flexion to represent contribution of hip flexion to trunk forward rotation). Results: Overall, reach distance was significantly correlated with the range of COM forward displacement (r=0.707). In HIP-S, reach distance and COM displacement significantly correlated with COM displacement (r=0.858) and trunk-hip ratio (r = 0.660), respectively. In ANKLE-S, reach distance significantly correlated with COM (r=0.912) and trunk forward rotation (r=0.880). Overall, COM displacement and trunk rotation were significant predictors for reach distance (R 2 = 0.878). Specifically, trunk-hip ratio (R 2 =0.435) and trunk forward rotation (R 2 = 0.676) were significant predictors of COM displacement in HIP-S and ANKLE-S, respectively. Conclusion. FRT appeared to be a valid test of dynamic balance ability, regardless of reach strategies. However, the contribution of the body kinematics differed between the hip and ankle strategies. 4375 We-Th, no. 38 (P56) Effect of weight bearing on ankle joint position sense L.-J. Hsu, S.-I. Lin, S.-W. Li, I.-J. Tsai, C.-F. Liao. Department of Physical
Therapy, National Cheng Kung University, Tainan, Taiwan Background: It is known that joint proprioceptive inputs play a major role in joint position sense (JPS). Muscle vibration that selectively activates primary muscle afferents has been found to lead to erroneous JPS in the upper extremity joints. The lower extremity joints frequently function while bearing the body weight. It is unclear if weight bearing (WB) would influence ankle JPS and if erroneous proprioceptive inputs induced by vibration would affect this process. The purpose of this study was to investigate the effect of WB and muscle vibration on ankle JPS. Method: Fifteen healthy young adults participated in this study. JPS was measured by joint repositioning test that required the subjects to perform ankle dorsiflexion (about 10°) from the resting position, stop motion, memorize the joint angle, return to the resting position, and then dorsiflex the same ankle again to the memorized angle. The test was conducted in seated position under 3 WB (0, 25%, 50% body weight) and 3 vibration (no, Achilles tendon, tibialis anterior) conditions. In non-weight bearing, both legs were suspended, while in other conditions WB percentage was manipulated by changing the chair height. Vicon 460 motion system was used to record the ankle joint
Poster Presentations
angle. The angle difference (?angle) was defined as the absolute value of the difference between the final angles of the 2 ankle dorsiflexion movements. Repeated measure ANOVA was used to test vibration by position effect. Result: There was no significant vibration main effect or vibration WB interaction. The angle was significantly larger in non-WB (2.32 ± 1.79 °) than in 25% WB (1.58± 1.38 °) or 50% WB (1.73± 1.52°). Conclusion: Somatosensory inputs from WB helped to increase the accuracy of ankle joint repositioning. What is more, this effect did not seem to be affected by erroneous proprioceptive inputs. Thus, somatosensory inputs from WB might have greater contribution than proprioceptive inputs in ankle position sense. 4419 We-Th, no. 39 (P56) Effect of deep brain stimulation on a rapid arm movement in Parkinson's disease K. Schneider 1, K. B6tzel 2, A. Born 1, K. Vetter 1. 1Institute of Sport Science and
Sports, Bundeswehr University Munich, Neubiberg, Germany, 2Department of Neurology, University of Munich (LMU), Munich, Germany Introduction: In deep brain stimulation (DBS) continuous electrical stimuli inhibit the neurons in the area of the implemented electrodes (internal globus pallidum or nucleus subthalamicus). With DBS the movement dysfunctions observed in Parkinson's disease (PD) are reduced, however, the mechanisms causing the improvement are only partly understood [1]. Here we report the effect of DBS (off versus on) on movement kinematics, and in addition, on movement dynamics during a rapid arm movement. The analyses of movement dynamics provide insight in the mechanical causes of the movement, and thus, in movement coordination while kinematical analyses quantity the effect. Methods: Eight PD patients performed a complex, maximal-speed vertical arm movement between two targets in the conditions DBS off versus on. The movement was recorded with a high-speed video motion analysis system (240 Hz). Six reflective markers were placed on the subject's arm and trunk. The three-dimensional coordinates for each marker were smoothed using a 6 Hz Butterworth filter. From the coordinates movement kinematics and dynamics were calculated. The subjects had given their informed consent and the study was medically supervised. Results: With DBS turned on, movement times significantly decreased. Hand paths and shoulder joint angle versus elbow joint angle patterns only moderately changed due to the task's constraints. Time series of hand velocities and accelerations as well as elbow and shoulder joint torques became smoother and larger in amplitude. In addition, shoulder joint torque versus elbow joint torque patterns in some of the subjects showed a coupling between shoulder and elbow joint whereas the patterns were erratic in the DBS off condition. These observations suggest that in the DBS on condition the underlying movement coordination was altered although comparable movement kinematics were produced (hand path, joint angles) while the movement task was performed significantly faster. References [1] Schenk et al. Neuropsychologia 2003; 41: 783-794.
4483 We-Th, no. 40 (P56) Optimal tendon compliance for maximising efficiency during locomotion G. Lichtwark 1, A. Wilson 1,2. 1Structure and Motion Laboratory, Royal
Veterinary College, Hatfield, Hertfordshire, UK, 2Structure and Motion Laboratory, Institute of Orthopaedics and Musculoskeletal Sciences, University College London, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, UK Tendon compliance is important in cyclical movements because it allows muscle fibres to shorten at speeds where they have high power outputs and efficiency. However, the optimal tendon stiffness to achieve maximum power output or efficiency is not known, nor whether tendons are designed with the goal of maximising either. Here we focus on the criterion for efficiency and determine the optimal human Achilles tendon stiffness to achieve maximum efficiency. We make the assumption that both the power output and the required kinematics are fixed for any given locomotion speed and condition (e.g. incline). We have used a Hill type muscle model to predict the muscle activation level and muscle fibre shortening required to produce the necessary force for any given series elastic element (SEE) stiffness during locomotion. We used previously determined muscle force and length changes of the human medial gastrocnemius from kinetic and kinematic data during walking and running and applied a model of muscle energetics to predict the efficiency of the muscle at different values of tendon stiffness. The results show that maximum efficiency is achieved at a different value of SEE compliance for walking compared to running while walking achieved a greater maximum muscle efficiency than running. In both conditions, maximum efficiency is achieved at SEE compliance values ranging from 0.5-1 times the value of the Achilles tendon. The SEE is a combination of both the Achilles tendon
Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
hypothesized that a standardized fitting technique could be used to ascertain important values (e.g., H-threshold, 50% Hmax, Hmax) for comparison and provide a reliable tool for researchers to analyze the H-reflex RC. The M-wave was fit using a sigmoid curve based on a logistic equation to mimic the physiologically-based predicted response to varying stimulus intensity. The optimal fit of the sigmoid curve to the M-wave was evaluated using a nonlinear least squares iterative fit to the M-wave data to provide the best values of both R 2 and RMSE. Due to the variable nature of the H-reflex RC, both the M and the H-wave were fit using a smoothing-spline interpolant. This method is relatively insensitive to the spacing of intensities and the variability in the data. The reliability of the fitted RC was tested by comparing the fitted data to the average H-reflex and M-wave data obtained from an experimental trial in which the stimulus intensity was held constant. The amplitude of the H- and M-responses taken from the constant intensity trials were 5 0 ± 16% Mmax 5 ± 3 % Mmax, respectively. The smoothing spline fitted data corresponding to the constant intensity value yielded an H-reflex amplitude of 49 ± 16% Mmax and an M-wave of 4 ± 4 % Mmax. The value obtained from the sigmoid curve fit to the M-wave was 7 ± 12% Mmax. Thus, these RC curve fitting techniques could provide a valuable analysis tool in H-reflex studies. Supported by NSERC. 4376 We-Th, no. 37 (P56) Effect of different movement patterns on functional reach C.-R Liao, S.-I. Lin. Department of Physical Therapy, National Cheng Kung
University, Tainan, Taiwan Background and Purpose: Functional reach test (FRT) is frequently used to measure dynamic standing balance. It is not clear if reach strategy would affect the association between reach distance and dynamic balance ability. The purposes of this study were to investigate the extent to which reach distance reflected dynamic balance and the contribution of movement kinematics to reach performance. Methods: Twenty-two young adults performed FRT involving standing with the feet shoulder width apart, raising one arm 900 , and then reaching forward as far as possible without moving the feet or losing balance. A 6-camera VICON motion system was used to record the body kinematics. A hip strategy (HIP-S) was defined as having the ankle move in the plantarflexing direction during reaching. An ankle strategy (ANKLE-S) was defined as beginning reaching with ankle dorsiflexion and with total hip flexion range smaller than 15 °. The variables of interest were reach distance, range of center of mass (COM) forward displacement, range of trunk, hip, and ankle angular displacement, and hip-trunk ratio (ratio between trunk and hip flexion to represent contribution of hip flexion to trunk forward rotation). Results: Overall, reach distance was significantly correlated with the range of COM forward displacement (r=0.707). In HIP-S, reach distance and COM displacement significantly correlated with COM displacement (r=0.858) and trunk-hip ratio (r = 0.660), respectively. In ANKLE-S, reach distance significantly correlated with COM (r=0.912) and trunk forward rotation (r=0.880). Overall, COM displacement and trunk rotation were significant predictors for reach distance (R 2 = 0.878). Specifically, trunk-hip ratio (R 2 =0.435) and trunk forward rotation (R 2 = 0.676) were significant predictors of COM displacement in HIP-S and ANKLE-S, respectively. Conclusion. FRT appeared to be a valid test of dynamic balance ability, regardless of reach strategies. However, the contribution of the body kinematics differed between the hip and ankle strategies. 4375 We-Th, no. 38 (P56) Effect of weight bearing on ankle joint position sense L.-J. Hsu, S.-I. Lin, S.-W. Li, I.-J. Tsai, C.-F. Liao. Department of Physical
Therapy, National Cheng Kung University, Tainan, Taiwan Background: It is known that joint proprioceptive inputs play a major role in joint position sense (JPS). Muscle vibration that selectively activates primary muscle afferents has been found to lead to erroneous JPS in the upper extremity joints. The lower extremity joints frequently function while bearing the body weight. It is unclear if weight bearing (WB) would influence ankle JPS and if erroneous proprioceptive inputs induced by vibration would affect this process. The purpose of this study was to investigate the effect of WB and muscle vibration on ankle JPS. Method: Fifteen healthy young adults participated in this study. JPS was measured by joint repositioning test that required the subjects to perform ankle dorsiflexion (about 10°) from the resting position, stop motion, memorize the joint angle, return to the resting position, and then dorsiflex the same ankle again to the memorized angle. The test was conducted in seated position under 3 WB (0, 25%, 50% body weight) and 3 vibration (no, Achilles tendon, tibialis anterior) conditions. In non-weight bearing, both legs were suspended, while in other conditions WB percentage was manipulated by changing the chair height. Vicon 460 motion system was used to record the ankle joint
Poster Presentations
angle. The angle difference (?angle) was defined as the absolute value of the difference between the final angles of the 2 ankle dorsiflexion movements. Repeated measure ANOVA was used to test vibration by position effect. Result: There was no significant vibration main effect or vibration WB interaction. The angle was significantly larger in non-WB (2.32 ± 1.79 °) than in 25% WB (1.58± 1.38 °) or 50% WB (1.73± 1.52°). Conclusion: Somatosensory inputs from WB helped to increase the accuracy of ankle joint repositioning. What is more, this effect did not seem to be affected by erroneous proprioceptive inputs. Thus, somatosensory inputs from WB might have greater contribution than proprioceptive inputs in ankle position sense. 4419 We-Th, no. 39 (P56) Effect of deep brain stimulation on a rapid arm movement in Parkinson's disease K. Schneider 1, K. B6tzel 2, A. Born 1, K. Vetter 1. 1Institute of Sport Science and
Sports, Bundeswehr University Munich, Neubiberg, Germany, 2Department of Neurology, University of Munich (LMU), Munich, Germany Introduction: In deep brain stimulation (DBS) continuous electrical stimuli inhibit the neurons in the area of the implemented electrodes (internal globus pallidum or nucleus subthalamicus). With DBS the movement dysfunctions observed in Parkinson's disease (PD) are reduced, however, the mechanisms causing the improvement are only partly understood [1]. Here we report the effect of DBS (off versus on) on movement kinematics, and in addition, on movement dynamics during a rapid arm movement. The analyses of movement dynamics provide insight in the mechanical causes of the movement, and thus, in movement coordination while kinematical analyses quantity the effect. Methods: Eight PD patients performed a complex, maximal-speed vertical arm movement between two targets in the conditions DBS off versus on. The movement was recorded with a high-speed video motion analysis system (240 Hz). Six reflective markers were placed on the subject's arm and trunk. The three-dimensional coordinates for each marker were smoothed using a 6 Hz Butterworth filter. From the coordinates movement kinematics and dynamics were calculated. The subjects had given their informed consent and the study was medically supervised. Results: With DBS turned on, movement times significantly decreased. Hand paths and shoulder joint angle versus elbow joint angle patterns only moderately changed due to the task's constraints. Time series of hand velocities and accelerations as well as elbow and shoulder joint torques became smoother and larger in amplitude. In addition, shoulder joint torque versus elbow joint torque patterns in some of the subjects showed a coupling between shoulder and elbow joint whereas the patterns were erratic in the DBS off condition. These observations suggest that in the DBS on condition the underlying movement coordination was altered although comparable movement kinematics were produced (hand path, joint angles) while the movement task was performed significantly faster. References [1] Schenk et al. Neuropsychologia 2003; 41: 783-794.
4483 We-Th, no. 40 (P56) Optimal tendon compliance for maximising efficiency during locomotion G. Lichtwark 1, A. Wilson 1,2. 1Structure and Motion Laboratory, Royal
Veterinary College, Hatfield, Hertfordshire, UK, 2Structure and Motion Laboratory, Institute of Orthopaedics and Musculoskeletal Sciences, University College London, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, UK Tendon compliance is important in cyclical movements because it allows muscle fibres to shorten at speeds where they have high power outputs and efficiency. However, the optimal tendon stiffness to achieve maximum power output or efficiency is not known, nor whether tendons are designed with the goal of maximising either. Here we focus on the criterion for efficiency and determine the optimal human Achilles tendon stiffness to achieve maximum efficiency. We make the assumption that both the power output and the required kinematics are fixed for any given locomotion speed and condition (e.g. incline). We have used a Hill type muscle model to predict the muscle activation level and muscle fibre shortening required to produce the necessary force for any given series elastic element (SEE) stiffness during locomotion. We used previously determined muscle force and length changes of the human medial gastrocnemius from kinetic and kinematic data during walking and running and applied a model of muscle energetics to predict the efficiency of the muscle at different values of tendon stiffness. The results show that maximum efficiency is achieved at a different value of SEE compliance for walking compared to running while walking achieved a greater maximum muscle efficiency than running. In both conditions, maximum efficiency is achieved at SEE compliance values ranging from 0.5-1 times the value of the Achilles tendon. The SEE is a combination of both the Achilles tendon