- Email: [email protected]
The influence of weakness on posture control: A simulation study
S8
Abstracts / Gait & Posture 42S (2015) S1–S90
References [1] Lubik S, Fogel W, Tronnier V, Krause M, König J, Jost WH. Gait analysis in patients with advanced Parkinson disease: different or additive effects on gait induced by levodopa and chronic STN stimulation. J Neural Transm 2006;113:163–73. [2] Krysthowiak P, Blatt JL, Bourriez JL, Duhamel A, Perina M, Blond S, et al. Effects of subthalamic nucleus stimulation and levodopa treatment on gait abnormalities in Parkinson disease. Arch Neurol 2003;60:80–4. [3] Botzel K, Kraft E. Strategies for treatment of gait and posture associated deficits in movement disorders: the impact of deep brain stimulation. Neurol Neurosci 2010;28:111–8.
http://dx.doi.org/10.1016/j.gaitpost.2015.03.026 The influence of weakness on posture control: A simulation study M. Afschrift 1,∗ , F. De Groote 2 , S. Verschueren 3 , J. De Schutter 2 , I. Jonkers 1 1 Human Movement Biomechanics Research Group, Department of Kinesiology, KU Leuven, Belgium 2 Division PMA, Department of Mechanical Engineering, KU Leuven, Belgium 3 Research Group for Musculoskeletal Rehabilitation, Department of Kinesiology, KU Leuven, Belgium
Main topics: Elderly, Posture, Simulation Introduction: The high incidence of falls in the elderly is a highly important topic in our ageing society. One of the factors that influence posture control in the elderly is the person’s capacity to generate stabilizing joint moments through coordinated muscle action [1]. However it is difficult to establish a causal relationship between weakness and balance control using an experimental approach due to many confounding variables. Therefore it’s difficult to predict the impact of weakness at a specific joint on posture control. Therefore, a simulation approach is used in the present study to evaluate the relative importance of the influence of ankle versus hip joint weakness on postural stability. This insight is however highly relevant for the design of effective fall prevention training, focussing either at the strengthening ankle or hip musculature. Methods: OpenSim was used to create a feedback control model based on a generic musculoskeletal model [2]. This model had six degrees of freedom (i.e. hip flexion/extension, knee flexion/extension and ankle plantarflexion/dorsiflexion of the right and left leg). A constraint was used to keep the feet flat on the ground during the simulation. The balance of the model was perturbed by a forward momentum of 37.5 N s acting at the centre of mass (COM) of the torso. Linear feedback of the whole body COM trajectory and torso orientation (position, velocity and acceleration) determined by feedback gains controlled the ideal moment actuators of the hips and ankles. Position, velocity and acceleration feedback gains followed from an optimization that minimizes the COM movement and actuator work. Weakness was induced by reducing the maximal moment generating capacities around the (1) ankle and (2) hip joint by 40%. Difference in ankle and hip kinematics and kinetics (especially work) were evaluated throughout the simulation duration (Fig. 1). Results: Weakness at the ankle joint has an important effect on the kinematics and kinetics required to restore postural stability (Table 1): there is an increase in anterior displacement of the COM and maximal hip and ankle range of motion (ROM). At the level of kinetics, there is an increase in the work provided by the ankle and hip actuators. Comparing the effect introduced by the ankle vs hip actuators, a similar amount of weakness at the ankle joint has amore effect on posture control than weakness at the hip joint as reflected in the analysed kinematics and kinetic parameters. In particular, there is an increase of 111% in anterior COM displacement and an increase of 53% in total work delivered by the actuators.
Fig. 1. The musculoskeletal model with COM feedback control to simulate posture control. Table 1 The influence of weakness on kinematic and kinetic variables of posture control.
Strong model Ankle weak Hip weak
COM movement
Hip ROM
Ankle ROM
Total work
Ankle work
Hip work
0.09 m 0.19 m 0.09 m
20◦ 45◦ 18◦
7◦ 22◦ 6◦
116 J 168 J 110 J
37 J 77 J 33 J
38 J 64 J 28 J
Discussion and conclusion: A forward simulation approach was used to quantify the influence of weakness around the ankle and hip joint on the posture control strategy. The results indicate that weakness around the ankle joint has a major influence on the posture control strategy. Persons with ankle weakness use a hip strategy that increases the hip contribution to control the COM movement. Despite its success in restoring balance, this strategy causes an increase in total work which influences metabolic energy consumption and fatigue. Weakness around the hip joint did not influence the posture control strategy to a similar extent. Therefore, this study suggests that effective fall prevention training programs should focus on increasing the strength of the muscles around the ankle joint. References [1] Tsai, et al. J Biomech 2014. [2] Delp, et al. IEEE Trans Biomed Eng 2007.
http://dx.doi.org/10.1016/j.gaitpost.2015.03.027
Abstracts / Gait & Posture 42S (2015) S1–S90
References [1] Lubik S, Fogel W, Tronnier V, Krause M, König J, Jost WH. Gait analysis in patients with advanced Parkinson disease: different or additive effects on gait induced by levodopa and chronic STN stimulation. J Neural Transm 2006;113:163–73. [2] Krysthowiak P, Blatt JL, Bourriez JL, Duhamel A, Perina M, Blond S, et al. Effects of subthalamic nucleus stimulation and levodopa treatment on gait abnormalities in Parkinson disease. Arch Neurol 2003;60:80–4. [3] Botzel K, Kraft E. Strategies for treatment of gait and posture associated deficits in movement disorders: the impact of deep brain stimulation. Neurol Neurosci 2010;28:111–8.
http://dx.doi.org/10.1016/j.gaitpost.2015.03.026 The influence of weakness on posture control: A simulation study M. Afschrift 1,∗ , F. De Groote 2 , S. Verschueren 3 , J. De Schutter 2 , I. Jonkers 1 1 Human Movement Biomechanics Research Group, Department of Kinesiology, KU Leuven, Belgium 2 Division PMA, Department of Mechanical Engineering, KU Leuven, Belgium 3 Research Group for Musculoskeletal Rehabilitation, Department of Kinesiology, KU Leuven, Belgium
Main topics: Elderly, Posture, Simulation Introduction: The high incidence of falls in the elderly is a highly important topic in our ageing society. One of the factors that influence posture control in the elderly is the person’s capacity to generate stabilizing joint moments through coordinated muscle action [1]. However it is difficult to establish a causal relationship between weakness and balance control using an experimental approach due to many confounding variables. Therefore it’s difficult to predict the impact of weakness at a specific joint on posture control. Therefore, a simulation approach is used in the present study to evaluate the relative importance of the influence of ankle versus hip joint weakness on postural stability. This insight is however highly relevant for the design of effective fall prevention training, focussing either at the strengthening ankle or hip musculature. Methods: OpenSim was used to create a feedback control model based on a generic musculoskeletal model [2]. This model had six degrees of freedom (i.e. hip flexion/extension, knee flexion/extension and ankle plantarflexion/dorsiflexion of the right and left leg). A constraint was used to keep the feet flat on the ground during the simulation. The balance of the model was perturbed by a forward momentum of 37.5 N s acting at the centre of mass (COM) of the torso. Linear feedback of the whole body COM trajectory and torso orientation (position, velocity and acceleration) determined by feedback gains controlled the ideal moment actuators of the hips and ankles. Position, velocity and acceleration feedback gains followed from an optimization that minimizes the COM movement and actuator work. Weakness was induced by reducing the maximal moment generating capacities around the (1) ankle and (2) hip joint by 40%. Difference in ankle and hip kinematics and kinetics (especially work) were evaluated throughout the simulation duration (Fig. 1). Results: Weakness at the ankle joint has an important effect on the kinematics and kinetics required to restore postural stability (Table 1): there is an increase in anterior displacement of the COM and maximal hip and ankle range of motion (ROM). At the level of kinetics, there is an increase in the work provided by the ankle and hip actuators. Comparing the effect introduced by the ankle vs hip actuators, a similar amount of weakness at the ankle joint has amore effect on posture control than weakness at the hip joint as reflected in the analysed kinematics and kinetic parameters. In particular, there is an increase of 111% in anterior COM displacement and an increase of 53% in total work delivered by the actuators.
Fig. 1. The musculoskeletal model with COM feedback control to simulate posture control. Table 1 The influence of weakness on kinematic and kinetic variables of posture control.
Strong model Ankle weak Hip weak
COM movement
Hip ROM
Ankle ROM
Total work
Ankle work
Hip work
0.09 m 0.19 m 0.09 m
20◦ 45◦ 18◦
7◦ 22◦ 6◦
116 J 168 J 110 J
37 J 77 J 33 J
38 J 64 J 28 J
Discussion and conclusion: A forward simulation approach was used to quantify the influence of weakness around the ankle and hip joint on the posture control strategy. The results indicate that weakness around the ankle joint has a major influence on the posture control strategy. Persons with ankle weakness use a hip strategy that increases the hip contribution to control the COM movement. Despite its success in restoring balance, this strategy causes an increase in total work which influences metabolic energy consumption and fatigue. Weakness around the hip joint did not influence the posture control strategy to a similar extent. Therefore, this study suggests that effective fall prevention training programs should focus on increasing the strength of the muscles around the ankle joint. References [1] Tsai, et al. J Biomech 2014. [2] Delp, et al. IEEE Trans Biomed Eng 2007.
http://dx.doi.org/10.1016/j.gaitpost.2015.03.027