Compensatory strategies for excessive muscle co-contraction at the ankle
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ESMAC 2012 abstract / Gait & Posture 38 (2013) S1–S116 S15 Discussion & conclusions: A skeletal muscle model was enhanced by a history phenomenon using a simple formula [1,2]. The history modification improves the existing muscle model and gives more accurate description of underlying activations in musculoskeletal system movement simulation. Though current techniques do not enable us to validate the result fully, the supple- ment improved description of skeletal muscle force and showed the importance of the modification in demanding tasks. References [1] Kosterina N, Westerblad H, Eriksson A. Mechanical work as predic- tor of force enhancement and force depression. Journal of Biomechanics 2009;42(11):1628–34. [2] Kosterina N, Westerblad H, Eriksson A. History effect and timing of force pro- duction introduced in a skeletal muscle model. Biomechanics and Modeling in Mechanobiology 2011, http://dx.doi.org/10.1007/s10237-011-0364-5 . http://dx.doi.org/10.1016/j.gaitpost.2013.07.037 O25 Compensatory strategies for excessive muscle co-contraction at the ankle Ruoli Wang 1 , Elena M. Gutierrez-Farewik 1,2 1 Royal Institute of Technology, Department of Mechanics, Stockholm, Sweden 2 Karolinska Institutet, Department of Women’s and Children’s Health, Stockholm, Sweden Introduction: Co-contraction is the concurrent activation of agonist and antagonist muscles (antagonistic pairs) across the same joint. In some gait disorders, e.g. spastic gait, the temporal sepa- ration and magnitude differences of activities between agonist & antagonist muscles are frequently attenuated and motor control becomes poor. The aim of this study was to identify the necessary compensatory mechanisms to overcome excessive co-contraction of the soleus-tibialis anterior pair using induced acceleration anal- ysis (IAA) to retain a normal walking pattern. Patients/materials and methods: Nine healthy adults (age: 30 ± 3 years) were examined using a motion capture system (Vicon MX40). Ground reaction forces were obtained from two force- plates (Kistler). Surface EMG signals (Motion Laboratory System) were recorded from the biceps femoris long head (BFLH), rectus femoris (RF), medial gastrocnemius (GAS), soleus (SOL), and tib- ialis anterior (TA) bilaterally. The simulations were performed in OpenSim, which consisted of scaling, inverse kinematics, residual reduction algorithm (RRA) and computed muscle control (CMC) [1]. IAA was used to compute contributions of primary ankle dor- sif/plantarflexors and knee flexor/extensors to the accelerations of ankle and knee joints. The agonist and antagonistic muscles can be identified by defining the one with lesser activation as antagonist [2]. Three co- contraction levels (normal, medium and high) were simulated by increasing the activation of the antagonist muscle. The response of other muscles to the excessive co-contraction of SOL-TA was computed by repeating CMC and IAA after constraining excitations of SOL-TA at each co-contraction level. Results: Discussion & conclusions: Results of the simulation indicated that with a high level of the SOL-TA co-contraction, one could still perform normal walking through other means. When increased co- contraction was simulated in the SOL-TA by increasing excitation of TA in the 2nd sub-phase, GAS was the largest compensator at the ankle and knee. In addition, the net joint accelerations from the ankle and knee muscles were generally unchanged, which indi- cated that the ankle and knee muscles alone are able to compensate for increased co-contraction at the ankle joint. References [1] Delp SL, et al. IEEE Transactions on Biomedical Engineering 2007. [2] Falconer K, et al. Electromyography and Clinical Neurophysiology 1985. http://dx.doi.org/10.1016/j.gaitpost.2013.07.038
Transcript of Compensatory strategies for excessive muscle co-contraction at the ankle
ESMAC 2012 abstract / Gait & Posture 38 (2013) S1–S116 S15
Discussion & conclusions: A skeletal muscle model wasenhanced by a history phenomenon using a simple formula [1,2].The history modification improves the existing muscle modeland gives more accurate description of underlying activations inmusculoskeletal system movement simulation. Though currenttechniques do not enable us to validate the result fully, the supple-ment improved description of skeletal muscle force and showedthe importance of the modification in demanding tasks.
References
[1] Kosterina N, Westerblad H, Eriksson A. Mechanical work as predic-tor of force enhancement and force depression. Journal of Biomechanics2009;42(11):1628–34.
[2] Kosterina N, Westerblad H, Eriksson A. History effect and timing of force pro-duction introduced in a skeletal muscle model. Biomechanics and Modeling inMechanobiology 2011, http://dx.doi.org/10.1007/s10237-011-0364-5.
http://dx.doi.org/10.1016/j.gaitpost.2013.07.037
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Compensatory strategies for excessive muscleco-contraction at the ankle
Ruoli Wang 1, Elena M. Gutierrez-Farewik 1,2
1 Royal Institute of Technology, Department ofMechanics, Stockholm, Sweden2 Karolinska Institutet, Department of Women’s andChildren’s Health, Stockholm, Sweden
Introduction: Co-contraction is the concurrent activation ofagonist and antagonist muscles (antagonistic pairs) across the samejoint. In some gait disorders, e.g. spastic gait, the temporal sepa-ration and magnitude differences of activities between agonist &antagonist muscles are frequently attenuated and motor controlbecomes poor. The aim of this study was to identify the necessarycompensatory mechanisms to overcome excessive co-contractionof the soleus-tibialis anterior pair using induced acceleration anal-ysis (IAA) to retain a normal walking pattern.
Patients/materials and methods: Nine healthy adults (age:30 ± 3 years) were examined using a motion capture system (ViconMX40). Ground reaction forces were obtained from two force-plates (Kistler). Surface EMG signals (Motion Laboratory System)were recorded from the biceps femoris long head (BFLH), rectusfemoris (RF), medial gastrocnemius (GAS), soleus (SOL), and tib-ialis anterior (TA) bilaterally. The simulations were performed inOpenSim, which consisted of scaling, inverse kinematics, residualreduction algorithm (RRA) and computed muscle control (CMC)
[1]. IAA was used to compute contributions of primary ankle dor-sif/plantarflexors and knee flexor/extensors to the accelerations ofankle and knee joints. The agonist and antagonistic muscles can beidentified by defining the one with lesser activation as antagonist[2]. Three co- contraction levels (normal, medium and high) weresimulated by increasing the activation of the antagonist muscle.The response of other muscles to the excessive co-contraction ofSOL-TA was computed by repeating CMC and IAA after constrainingexcitations of SOL-TA at each co-contraction level.
Results:
Discussion & conclusions: Results of the simulation indicatedthat with a high level of the SOL-TA co-contraction, one could stillperform normal walking through other means. When increased co-contraction was simulated in the SOL-TA by increasing excitationof TA in the 2nd sub-phase, GAS was the largest compensator atthe ankle and knee. In addition, the net joint accelerations fromthe ankle and knee muscles were generally unchanged, which indi-cated that the ankle and knee muscles alone are able to compensatefor increased co-contraction at the ankle joint.
References
[1] Delp SL, et al. IEEE Transactions on Biomedical Engineering 2007.[2] Falconer K, et al. Electromyography and Clinical Neurophysiology 1985.
http://dx.doi.org/10.1016/j.gaitpost.2013.07.038
