Exoskeleton assistance symmetry matters: unilateral assistance reduces metabolic cost, but relatively less than bilateral assistance

Malcolm, Philippe; Galle, Samuel; Berghe, Pieter Van den; Clercq, Dirk De

doi:10.1186/s12984-018-0381-z

Cited by 25 publications

(16 citation statements)

References 53 publications

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“…A larger effect in bilateral affected persons on walking energy cost may can be explained by the fact that in unilateral affected persons the gait pattern remained asymmetric despite the AFO assistance. As gait symmetry has been shown important for gait efficiency, this might explain the modest effect of AFO stiffness optimization on walking energy cost in unilateral affected persons [34]. The effect of stiffness-optimized AFOs on walking energy cost and walking speed slightly declined between the post-provision and 3 months follow-up measurement (Figure 3), which was also found in a previous publication in children with cerebral palsy using a spring-hinged AFO [31].…”

Section: Discussionsupporting

confidence: 72%

Stiffness-Optimized Ankle-Foot Orthoses Improve Walking Energy Cost Compared to Conventional Orthoses in Neuromuscular Disorders: A Prospective Uncontrolled Intervention Study

Waterval

Brehm

Altmann

et al. 2020

IEEE Trans. Neural Syst. Rehabil. Eng.

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In persons with calf muscle weakness, walking energy cost is commonly increased due to persistent knee flexion and a diminished push-off. Provided ankle-foot orthoses (AFOs) usually lower walking energy cost. To maximize the reduction in energy cost, AFO bending stiffness should be individually optimized, but this is not common practice. Therefore, we aimed to evaluate whether individually stiffnessoptimized AFOs reduce walking energy cost compared to conventional AFOs in persons with non-spastic calf muscle weakness and, secondarily, whether stiffness-optimized AFOs improve walking speed and gait biomechanics. Thirty-seven persons with non-spastic calf muscle weakness using a conventional AFO were included. Participants were provided a new, individually stiffness-optimized AFO. Walking energy cost, speed and gait biomechanics were assessed, at delivery and 3-months follow-up. Stiffness-optimized AFOs reduced walking energy cost with 9.2% (-0.42J/kg/m, 95%CI: 0.26 to 0.57) compared to the conventional AFOs while walking speed increased with 5.2% (+0.05m/s, 95%CI: 0.03 to 0.08). In bilateral affected persons the effects were larger compared to unilateral affected persons (difference effect energy cost: 0.31J/kg/m, speed: +0.09m/s). Although individually gait biomechanics changed considerably, no significant group differences were found (p>0.118). We demonstrated that individually stiffness-optimized AFOs considerably and meaningfully reduced walking energy cost compared to conventional AFOs, which was accompanied by an increase in walking speed. Especially in bilateral affected persons large effects of stiffness-optimization were found. The individual differences in gait changes substantiate the recommendation This work was supported by Prinses Beatrix Spierfonds under grant [W.OR

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Section: Discussionsupporting

confidence: 72%

Stiffness-Optimized Ankle-Foot Orthoses Improve Walking Energy Cost Compared to Conventional Orthoses in Neuromuscular Disorders: A Prospective Uncontrolled Intervention Study

Waterval

Brehm

Altmann

et al. 2020

IEEE Trans. Neural Syst. Rehabil. Eng.

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“…the total assistance is provided unilaterally with the users wearing the PAFOs on both legs). Thus, based on the results found in [58], bigger reductions of the metabolic cost during the assisted walking trials (as compared to ZT) might have been obtained if the same total assistance would have been distributed over the two legs.…”

Section: Discussionmentioning

confidence: 95%

“…A recent study [58] showed that the uni-/bi-lateral configuration of the actuator influences the performance of the actuator in reducing the metabolic cost of walking in healthy subjects. More specifically, the study showed that a given amount of assistance from a PAFO is more efficient in reducing the metabolic cost of walking when it is evenly distributed over both legs (i.e.…”

Section: Discussionmentioning

confidence: 99%

Walking with a powered ankle-foot orthosis: the effects of actuation timing and stiffness level on healthy users

Moltedo

Baček

Serrien

et al. 2020

J NeuroEngineering Rehabil

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Background: In the last decades, several powered ankle-foot orthoses have been developed to assist the ankle joint of their users during walking. Recent studies have shown that the effects of the assistance provided by powered ankle-foot orthoses depend on the assistive profile. In compliant actuators, the stiffness level influences the actuator's performance. However, the effects of this parameter on the users has not been yet evaluated. The goal of this study is to assess the effects of the assistance provided by a variable stiffness ankle actuator on healthy young users. More specifically, the effect of different onset times of the push-off torque and different actuator's stiffness levels has been investigated. Methods: Eight healthy subjects walked with a unilateral powered ankle-foot orthosis in several assisted walking trials. The powered orthosis was actuated in the sagittal plane by a variable stiffness actuator. During the assisted walking trials, three different onset times of the push-off assistance and three different actuator's stiffness levels were used. The metabolic cost of walking, lower limb muscles activation, joint kinematics, and gait parameters measured during different assisted walking trials were compared to the ones measured during normal walking and walking with the powered orthosis not providing assistance. Results: This study found trends for more compliant settings of the ankle actuator resulting in bigger reductions of the metabolic cost of walking and soleus muscle activation in the stance phase during assisted walking as compared to the unassisted walking trial. In addition to this, the study found that, among the tested onset times, the earlier ones showed a trend for bigger reductions of the activation of the soleus muscle during stance, while the later ones led to a bigger reduction in the metabolic cost of walking in the assisted walking trials as compared to the unassisted condition. Conclusions: This study presents a first attempt to show that, together with the assistive torque profile, also the stiffness level of a compliant ankle actuator can influence the assistive performance of a powered ankle-foot orthosis.

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“…Thus, the BS can inform the therapists and teach the users about when they should perform the paretic and non-paretic limb's heel-strike, respectively, synchronizing the paretic and non-paretic foot-floor contact. This wearable BS showed to have the potential to boost the symmetric gait recovery that is still a challenge in unilateral robotic gait assistance [18].…”

Section: A System's Operabilitymentioning

confidence: 99%

Design and technical validation of a wearable biofeedback system for robotic gait rehabilitation

Pinheiro

Lopes

Figueiredo

et al. 2020

2020 IEEE International Conference on Autonomous Robot Systems and Competitions (ICARSC)

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Gait disabilities affect the human quality of life. Current directions for time-effective robotic gait rehabilitation require the inclusion of biofeedback systems (BSs) as a complementary robotic tool for efficient motor relearning. This work aims to present the user-centered design and validation of a wearable BS to foster users' active participation and enable therapists' effective participation during robotic gait rehabilitation driven by active orthoses. The multimodal BS comprises a development board to manage the activation of the stimuli (vibrotactile through the vibrotactile waist and shank bands, sonorous via single earphone, and visual using RGB LED) according to data tracked by orthosis embedded sensors. The BS's versatility allows its functioning as a modular and stand-alone system or integrated into the orthotic system. The system's operability was validated with four healthy subjects walking on a treadmill with the orthotic system and BS at 1 km/h. The results showed an operable system with good usability during robotic gait rehabilitation. This wearable BS has the potential to boost symmetric gait recovery and to effectively augment the user's active participation during robotic gait therapy; thus, contributing to accelerating the user's motor recovery.

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Exoskeleton assistance symmetry matters: unilateral assistance reduces metabolic cost, but relatively less than bilateral assistance

Cited by 25 publications

References 53 publications

Stiffness-Optimized Ankle-Foot Orthoses Improve Walking Energy Cost Compared to Conventional Orthoses in Neuromuscular Disorders: A Prospective Uncontrolled Intervention Study

Stiffness-Optimized Ankle-Foot Orthoses Improve Walking Energy Cost Compared to Conventional Orthoses in Neuromuscular Disorders: A Prospective Uncontrolled Intervention Study

Walking with a powered ankle-foot orthosis: the effects of actuation timing and stiffness level on healthy users

Design and technical validation of a wearable biofeedback system for robotic gait rehabilitation

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