- Email: [email protected]
Motor adaptation during dorsiflexion-assisted walking with a powered orthosis
Track 2. Musculoskeletal Mechanics-Joint ISB Track (CODAmotion MPX30), force plate (AMTI; 2000 Hz), electromyographic (EMG) (MA-310; 2000 Hz), and video (200 Hz) data were collected during treadmill walking with condition changes from minimal-to-maximal AFO stiffness or maximal-to-minimal AFO stiffness. Time-frequency analysis, using wavelets, was used for EMG analysis to quantify low (25-82 Hz) and high (142-301 Hz) frequency content. We found that humans adapted their muscle activation patterns to AFO resistance changes within one stride of AFO condition change, and the level of frictional resistance applied to the axis of ankle joint motion with the use of AFOs affected lower extremity muscle activity while kinematic and kinetic variables remained unchanged. Changes in muscle activation patterns preserved a preferred movement pattern likely to minimize the effect of the frictional resistance applied, as revealed by the minimal changes in joint angles and ground reaction forces as a function of AFO condition. Changes in EMG intensity and co-activation of antagonist muscles were time and frequency dependent. Using varied AFO stiffness to alter muscle activation patterns may assist in reducing locomotion metabolic costs in clinical populations. References [1] van Hedel H.J., Dietz V. Arch Phys Med Rehabil 2004; 85: 972-979. [2] Pang M.Y.C., Yang J.F. J Physiol 2001; 533: 617~25. 7600 Tu, 14:30-14:45 (P21) Determination of appropriate power for artificial muscles in lower limb orthosis K. Kim 1, '~-Y. Kim 2, R. Munho3, T.-K. Kwon 3, C.-U. Hong 3, N.-G. Kim 3.
1Department of Biomedical Engineering, Chonbuk National University, Jeonju-si, South Korea, 2Center for Healthcare Technology Development, Chonbuk National University, Jeonju-si, South Korea, 3Division of Bionics and Bioinformatics, Chonbuk National University, Jeonju-si, South Korea We have developed a gait assistance device for lower limb with a pneumatic rubber actuator, which is intended to assist and enhance lower limb muscular activities. Compared to other gait assistive devices being developed by other researchers, our device is designed especially for aged people and intended only for slight assistance so that the subjects can keep their muscular strength. For this purpose, we are investigating appropriate amount of power pattern of the device and investigating the effectiveness of the system. Therefore, we analyzed and measured muscular power and motion in the lower limbs during squat motion and gait with various loads based on motion analysis and electromyography analysis of major muscles in lower limbs. The muscles of interest were rectus femoris, biceps femoris, tibialis anterior and gastrocnemius in the lower limbs. A series of experiments were performed with younger volunteers. In the experiments, optoelectric motion analysis system, force platforms and electromyography device were used. The subjects performed the squat motion on force platforms with and without the lower limb orthosis in turn and the motion and muscular activities were closely tracked and analyzed. Based on motion analysis results and electromyography, the Ioadings to various muscles were approximated with a computational biomechanics model. 7577 Tu, 14:45-15:00 (P21) Locomotor adaptation to a powered ankle-foot orthosis: Comparison of footswitch control versus soleus proportional myoelectric control S.M. Cain 1, K.E. Gordon 2, D.P. Ferris 1,2. 1Biomedical Engineering and
2Movement Science, University of Michigan, Ann Arbor, MI, USA We studied locomotor adaptation to a powered ankle-foot orthosis with the intent of identifying adaptation differences between two different controllers. The first control mode used a footswitch to provide bang-bang control and the second control mode used a proportional myoelectric signal from the soleus. Both controllers activated an artificial pneumatic muscle providing plantar flexion torque. Subjects walked on a treadmill for two thirty-minute sessions spaced three days apart under either footswitch control (n =6) or myoelectric control (n =6). We recorded lower limb electromyography, joint kinematics, and orthosis kinetics. Four primary measures were used to compare adaptation and adaptation rates: stance phase EMG root-mean-squared (RMS), correlation of gait cycle EMG signals with normal (no pneumatic muscle), correlation of joint angles over the gait cycle with normal, and work done by the powered AFO. Results demonstrated significant differences in locomotor adaptation between control modes. At the end of the second session, subjects using myoelectric control had reduced soleus RMS more than the footswitch control subjects (70% vs. 95% of normal) and changed soleus activation patterns more than the footswitch control subjects (correlation of 0.65 vs. 0.82). These changes allowed the soleus control subjects to restore ankle kinematics closer to normal (correlation of 0.82 vs. 0.67 for footswitch subjects) and reduce the negative work done by the AFO (6% vs. 14% of the gross work). These results provide evidence that the controller can greatly alter how humans adapt to powered orthosis assistance during walking. Specifically, using a control mode that is directly linked to the nervous system via proportional myoelectric control
2.3. Motor Control of Human Movement
$31
allows for much faster adaptation in walking dynamics. Supported by NIH R01NS045486. 7031 Tu, 15:00-15:15 (P21) Motor adaptation during dorsiflexion-assisted walking with a powered orthosis P.-C. Kao 1, D.P. Ferris 1,2. 1Movement Science and 2Biomedical Engineering,
University of Michigan, Ann Arbor, MI, USA Drop foot is one of the most common gait deficits in post-stroke patients. Rigid ankle-foot orthoses (AFO) are frequently prescribed for correcting drop foot gait. Recent studies have found that long-term AFO use does not reduce muscle activation of ankle dorsiflexors or influence muscle strength restoration. However, the main drawbacks of rigid AFOs are that they impede pushoff plantarflexion and do not allow the user to make step-to-step changes in motion dynamics (e.g. stairs, obstacles, etc.). The purpose of this study was to examine how people adapt to an active dorsiflexion assist orthosis proportionally controlled by tibialis anterior EMG. Three healthy subjects were fitted with custom-made orthoses that included artificial pneumatic muscles providing dorsiflexor torque. A real time controller modulated force in the artificial muscle proportional to tibialis anterior EMG amplitude via a pressure regulator. We collected lower body kinematics, EMG, and artificial muscle force while subjects walked on a treadmill for 2 training sessions. Each session included 30 minutes of walking with the orthosis active and there was a 3-day break between the sessions. During the first minute on Day 1, exoskeleton dorsiflexor torque (peak -0.285 Nm/kg) substantially increased dorsiflexion at initial heel contact and during swing phase (both by -10 degrees). Throughout the active trials, subjects walked with increased ankle dorsiflexion and had tibialis anterior muscle activation patterns similar to passive orthosis trials. By the end of Day 2, subjects did not reduce tibialis anterior EMG amplitude compared to the first minute of Day 1 (EMG RMS 79.07% at Day 1, Minute 1 vs. 78.98% at Day 2, Minute 30) (EMG RMS values were normalized to the maximum value recorded in each subject at Day 1, Minute 1). Additional trials are necessary to extend the results to longer durations and continuous use. However, these findings suggest that active orthoses controlled by neural signals hold considerable potential for assisting people with drop-foot gait without producing decreases in muscle recruitment and strength. Supported by NIH R01NS045486. 6963 Tu, 15:15-15:30 (P21) An approach for the development of a fuzzy logic controller for the correction of the drop-foot syndrome V.N. Syrimpeis 1, V.C. Moulianitis1, E.I. Zerikiotis 1, N.A. Aspragathos 1, E.C. Panagiotopoulos2. 1Mechanical & Aeronautics Engineering Department,
University of Patras, Greece, 2Department of Orthopaedic Surgery, General University Hospital of Patras, Greece This paper presents a biomechatronics approach for the development of a Fuzzy Logic Control System (FLCS) for the rehabilitation of a neuromuscular disability, known as the Drop-Foot Syndrome, using Functional Electrical Stimulation (FES). The development of the FLCS is based on the knowledge concerning the humans walk acquired from gait analysis data and normal Electromyograms (EMG) of the lower limb. In the considered case, it is supposed that the DropFoot Syndrome is appeared due to peroneal nerve pathology, while Tibialis Anterior and Extensor Digitorum Longus, which are the muscles responsible for dorsiflexing (lifting) the foot, are intact. An EMG of a normal muscle is the input of the FLCS while the output is the stimulation patterns to Tibialis Anterior and Extensor Digitorum Longus muscles. Prototypes are not used for Tibialis Anterior and Extensor Digitorum Longus muscles since the patients gait rhythm is controlled by the rhythm of the normal muscle. The development of the FLCS is described in details and their efficiency is tested by the application of the FLCS to a simulated leg towards the rehabilitation of the Drop-Foot Syndrome. The difference between the ankle joint angle obtained by the proposed approach and the desired angle values is used as a measure to evaluate the performance of the FLCS. The bounded error ensures a safe dorsiflexion of the foot in a gait cycle. The simulations carried out with normal EMGs acquired from the Sartorius, Iliacus and Rectus Femoris muscles in order to show the adaptability of the proposed approach. The results are encouraging for further research towards the proposed approach.
1Department of Biomedical Engineering, Chonbuk National University, Jeonju-si, South Korea, 2Center for Healthcare Technology Development, Chonbuk National University, Jeonju-si, South Korea, 3Division of Bionics and Bioinformatics, Chonbuk National University, Jeonju-si, South Korea We have developed a gait assistance device for lower limb with a pneumatic rubber actuator, which is intended to assist and enhance lower limb muscular activities. Compared to other gait assistive devices being developed by other researchers, our device is designed especially for aged people and intended only for slight assistance so that the subjects can keep their muscular strength. For this purpose, we are investigating appropriate amount of power pattern of the device and investigating the effectiveness of the system. Therefore, we analyzed and measured muscular power and motion in the lower limbs during squat motion and gait with various loads based on motion analysis and electromyography analysis of major muscles in lower limbs. The muscles of interest were rectus femoris, biceps femoris, tibialis anterior and gastrocnemius in the lower limbs. A series of experiments were performed with younger volunteers. In the experiments, optoelectric motion analysis system, force platforms and electromyography device were used. The subjects performed the squat motion on force platforms with and without the lower limb orthosis in turn and the motion and muscular activities were closely tracked and analyzed. Based on motion analysis results and electromyography, the Ioadings to various muscles were approximated with a computational biomechanics model. 7577 Tu, 14:45-15:00 (P21) Locomotor adaptation to a powered ankle-foot orthosis: Comparison of footswitch control versus soleus proportional myoelectric control S.M. Cain 1, K.E. Gordon 2, D.P. Ferris 1,2. 1Biomedical Engineering and
2Movement Science, University of Michigan, Ann Arbor, MI, USA We studied locomotor adaptation to a powered ankle-foot orthosis with the intent of identifying adaptation differences between two different controllers. The first control mode used a footswitch to provide bang-bang control and the second control mode used a proportional myoelectric signal from the soleus. Both controllers activated an artificial pneumatic muscle providing plantar flexion torque. Subjects walked on a treadmill for two thirty-minute sessions spaced three days apart under either footswitch control (n =6) or myoelectric control (n =6). We recorded lower limb electromyography, joint kinematics, and orthosis kinetics. Four primary measures were used to compare adaptation and adaptation rates: stance phase EMG root-mean-squared (RMS), correlation of gait cycle EMG signals with normal (no pneumatic muscle), correlation of joint angles over the gait cycle with normal, and work done by the powered AFO. Results demonstrated significant differences in locomotor adaptation between control modes. At the end of the second session, subjects using myoelectric control had reduced soleus RMS more than the footswitch control subjects (70% vs. 95% of normal) and changed soleus activation patterns more than the footswitch control subjects (correlation of 0.65 vs. 0.82). These changes allowed the soleus control subjects to restore ankle kinematics closer to normal (correlation of 0.82 vs. 0.67 for footswitch subjects) and reduce the negative work done by the AFO (6% vs. 14% of the gross work). These results provide evidence that the controller can greatly alter how humans adapt to powered orthosis assistance during walking. Specifically, using a control mode that is directly linked to the nervous system via proportional myoelectric control
2.3. Motor Control of Human Movement
$31
allows for much faster adaptation in walking dynamics. Supported by NIH R01NS045486. 7031 Tu, 15:00-15:15 (P21) Motor adaptation during dorsiflexion-assisted walking with a powered orthosis P.-C. Kao 1, D.P. Ferris 1,2. 1Movement Science and 2Biomedical Engineering,
University of Michigan, Ann Arbor, MI, USA Drop foot is one of the most common gait deficits in post-stroke patients. Rigid ankle-foot orthoses (AFO) are frequently prescribed for correcting drop foot gait. Recent studies have found that long-term AFO use does not reduce muscle activation of ankle dorsiflexors or influence muscle strength restoration. However, the main drawbacks of rigid AFOs are that they impede pushoff plantarflexion and do not allow the user to make step-to-step changes in motion dynamics (e.g. stairs, obstacles, etc.). The purpose of this study was to examine how people adapt to an active dorsiflexion assist orthosis proportionally controlled by tibialis anterior EMG. Three healthy subjects were fitted with custom-made orthoses that included artificial pneumatic muscles providing dorsiflexor torque. A real time controller modulated force in the artificial muscle proportional to tibialis anterior EMG amplitude via a pressure regulator. We collected lower body kinematics, EMG, and artificial muscle force while subjects walked on a treadmill for 2 training sessions. Each session included 30 minutes of walking with the orthosis active and there was a 3-day break between the sessions. During the first minute on Day 1, exoskeleton dorsiflexor torque (peak -0.285 Nm/kg) substantially increased dorsiflexion at initial heel contact and during swing phase (both by -10 degrees). Throughout the active trials, subjects walked with increased ankle dorsiflexion and had tibialis anterior muscle activation patterns similar to passive orthosis trials. By the end of Day 2, subjects did not reduce tibialis anterior EMG amplitude compared to the first minute of Day 1 (EMG RMS 79.07% at Day 1, Minute 1 vs. 78.98% at Day 2, Minute 30) (EMG RMS values were normalized to the maximum value recorded in each subject at Day 1, Minute 1). Additional trials are necessary to extend the results to longer durations and continuous use. However, these findings suggest that active orthoses controlled by neural signals hold considerable potential for assisting people with drop-foot gait without producing decreases in muscle recruitment and strength. Supported by NIH R01NS045486. 6963 Tu, 15:15-15:30 (P21) An approach for the development of a fuzzy logic controller for the correction of the drop-foot syndrome V.N. Syrimpeis 1, V.C. Moulianitis1, E.I. Zerikiotis 1, N.A. Aspragathos 1, E.C. Panagiotopoulos2. 1Mechanical & Aeronautics Engineering Department,
University of Patras, Greece, 2Department of Orthopaedic Surgery, General University Hospital of Patras, Greece This paper presents a biomechatronics approach for the development of a Fuzzy Logic Control System (FLCS) for the rehabilitation of a neuromuscular disability, known as the Drop-Foot Syndrome, using Functional Electrical Stimulation (FES). The development of the FLCS is based on the knowledge concerning the humans walk acquired from gait analysis data and normal Electromyograms (EMG) of the lower limb. In the considered case, it is supposed that the DropFoot Syndrome is appeared due to peroneal nerve pathology, while Tibialis Anterior and Extensor Digitorum Longus, which are the muscles responsible for dorsiflexing (lifting) the foot, are intact. An EMG of a normal muscle is the input of the FLCS while the output is the stimulation patterns to Tibialis Anterior and Extensor Digitorum Longus muscles. Prototypes are not used for Tibialis Anterior and Extensor Digitorum Longus muscles since the patients gait rhythm is controlled by the rhythm of the normal muscle. The development of the FLCS is described in details and their efficiency is tested by the application of the FLCS to a simulated leg towards the rehabilitation of the Drop-Foot Syndrome. The difference between the ankle joint angle obtained by the proposed approach and the desired angle values is used as a measure to evaluate the performance of the FLCS. The bounded error ensures a safe dorsiflexion of the foot in a gait cycle. The simulations carried out with normal EMGs acquired from the Sartorius, Iliacus and Rectus Femoris muscles in order to show the adaptability of the proposed approach. The results are encouraging for further research towards the proposed approach.