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--- start [2020/01/08 13:05]
Martin Grimmer
+++ start [2020/02/28 10:15]
Christian
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 ====== Latest Publications ======
-==== Review of balance recovery in response to external perturbations during daily activities  ====
-Balance related responses to perturbations were investigated in one of our latest studies by Dr. Dario Tokur, Dr. [[lab_members:lab_members_martingrimmer|Martin Grimmer]] and Prof. Andre Seyfarth. The work was recently published in [[https://doi.org/10.1016/j.humov.2019.102546|Human Movement Science]].
+===== Biarticular muscles in light of template models, experiments and robotics: a review =====
-{{ ::perturbation.png?400|}}
+Read our recent review paper about biarticular muscles to learn about the scientific discoveries from simulation models, evidence from human experiments and beneficial design principles in robotic applications. Link to the published paper (open access): [[https://doi.org/10.1098/rsif.2018.0413|Link to Royal Society Interface]].
+{{ :props_muscles.jpg?nolink&200|[[https://doi.org/10.1098/rsif.2018.0413|Link to Royal Society Interface]] }}
 **Abstract:**
-Balance is an essential capability to ensure upright standing and locomotion. Various external perturbations challenge our balance in daily life and increase the risk for falling and associated injury. Researchers try to identify the human mechanisms to maintain balance by intentional perturbations. The objectives of this work were to point out which areas of perturbation based research are well covered and not well covered and to extract which coping mechanisms humans use to respond to external perturbations. A literature review was performed to analyze mechanisms in response to external perturbations such as pushes to the body or ground level changes during standing, walking, running and hopping. To get a well-structured overview on the two dimensions, the perturbation type and the task, the Perturbation Matrix (PMA) was designed. We found that multiple studies exist for the tasks walking and standing, while hopping and running are covered less. However, all tasks still offer opportunities for both in-depth and fundamental research. Regarding the recovery mechanisms we found that humans can recover from various types of perturbations with versatile mechanisms using combinations of trunk, as well as upper and lower limb movements. The recovery movements will adapt depending on the perturbation intensity, direction and timing. Changes in joint kinetics, joint kinematics and muscle activity were identified on the joint level and leg stiffness and leg length on the global leg level. We believe that the insights from the extracted mechanisms may be applied to the hardware and control of robotic limbs or lower limb exoskeletons to improve the balance and robustness during standing or locomotion.
+Leg morphology is an important outcome of evolution. A remarkable morphological leg feature is the existence of biarticular muscles that span adjacent joints. Diverse studies from different fields of research suggest a less coherent understanding of the muscles’ functionality in cyclic, sagittal plane locomotion. We structured this review of biarticular muscle function by reflecting biomechanical template models, human experiments and robotic system designs. Within these approaches, we surveyed the contribution of biarticular muscles to the locomotor subfunctions (stance, balance and swing). While mono- and biarticular muscles do not show physiological differences, the reviewed studies provide evidence for complementary and locomotor subfunction-specific contributions of mono- and biarticular muscles. In stance, biarticular muscles coordinate joint movements, improve economy (e.g. by transferring energy) and secure the zig-zag configuration of the leg against joint overextension. These commonly known functions are extended by an explicit role of biarticular muscles in controlling the angular momentum for balance and swing. Human-like leg arrangement and intrinsic (compliant) properties of biarticular structures improve the controllability and energy efficiency of legged robots and assistive devices. Future interdisciplinary research on biarticular muscles should address their role for sensing and control as well as non-cyclic and/or non-sagittal motions, and non-static moment arms. \\
-For further projects and publications of [[lab_members:lab_members_martingrimmer|M. Grimmer]] please check: [[https://www.researchgate.net/profile/Martin_Grimmer3|ResearchGate]], [[https://scholar.google.de/citations?hl=de&user=gDF_uHUAAAAJ&view_op=list_works&sortby=pubdate|Google Scholar]], [[https://orcid.org/0000-0003-1921-1433|ORCID]] or [[https://loop.frontiersin.org/people/390560/overview|LOOP]]
+==== Human Lower Limb Joint Biomechanics in Daily Life Activities: A Literature Based Requirement Analysis for Anthropomorphic Robot Design  ====
-\\
-==== Biomechanical effects of passive hip springs during walking  ====
+Human lower limb biomechanics of daily activities were investigated in one of our latest studies by [[lab_members:lab_members_martingrimmer|Martin Grimmer]], Ahmed Elshamanhory and Philipp Beckerle. The work was recently published in [[https://doi.org/10.3389/frobt.2020.00013|Frontiers in Robotics and AI]]. The analyzed data is available as supplementary material [[https://www.frontiersin.org/articles/10.3389/frobt.2020.00013/full#supplementary-material|Matlab file]].
-The effects of passive springs at the hip were investigated in a collaboration project of Florian Haufe, Peter Wolf and Robert Riener from the [[https://sms.hest.ethz.ch/|Sensory-Motor Systems Lab]] from ETH Zurich and [[lab_members:lab_members_martingrimmer|Martin Grimmer]] from the Lauflabor. The work was recently published in the [[https://www.sciencedirect.com/science/article/abs/pii/S0021929019306797|Journal of Biomechanics]].
-{{ ::passive_hip_spring.jpg?400|}}
+{{ ::human_range_of_motion.jpg?600|}}
 **Abstract:**
+Daily human activity is characterized by a broad variety of movement tasks. This work summarizes the sagittal hip, knee, and ankle joint biomechanics for a broad range of daily movements, based on previously published literature, to identify requirements for robotic design. Maximum joint power, moment, angular velocity, and angular acceleration, as well as the movement-related range of motion and the mean absolute power were extracted, compared, and analyzed for essential and sportive movement tasks. We found that the full human range of motion is required to mimic human like performance and versatility. In general, sportive movements were found to exhibit the highest joint requirements in angular velocity, angular acceleration, moment, power, and mean absolute power. However, at the hip, essential movements, such as recovery, had comparable or even higher requirements. Further, we found that the moment and power demands were generally higher in stance, while the angular velocity and angular acceleration were mostly higher or equal in swing compared to stance for locomotion tasks. The extracted requirements provide a novel comprehensive overview that can help with the dimensioning of actuators enabling tailored assistance or rehabilitation for wearable lower limb robots, and to achieve essential, sportive or augmented performances that exceed natural human capabilities with humanoid robots.
-Passive spring-like structures can store and return energy during cyclic movements and thereby reduce the energetic cost of locomotion. That makes them important components of the human body and wearable assistive devices alike. This study investigates how springs placed anteriorly across the hip joint affect leg joint angles and powers, and leg muscle activities during level walking at 0.5 to 2.1 m/s.
-We hypothesized that the anterior hip springs (I) load hip extension, (II) support hip flexion and (III) affect ankle muscle activity and dynamics during walking. Effects at the ankle were expected because hip and ankle redistribute segmental power in concert to achieve forward progression.
-We observed that the participants’ contribution to hip power did not increase during hip extension as the spring stored energy. Simultaneously, the activities of plantarflexor muscles that modulate energy storage in the Achilles tendon were reduced by 28% (gastrocnemius medialis) and 9% (soleus). As the spring returned energy with the onset of hip flexion, the participants’ contribution to hip power was reduced by as much as 23%. Soleus activity before push-off increased by up to 9%.
-Instead of loading hip extension, anterior hip springs seem to store and return parts of the energy normally exchanged with the Achilles tendon. Thereby, the springs support hip flexion but may reduce elastic energy storage in and hence recoil from the Achilles tendon. This interaction should be considered during the design and simulation of wearable assistive devices as it might – depending on user characteristics – enhance or diminish their overall functionality.
 For further projects and publications of [[lab_members:lab_members_martingrimmer|M. Grimmer]] please check: [[https://www.researchgate.net/profile/Martin_Grimmer3|ResearchGate]], [[https://scholar.google.de/citations?hl=de&user=gDF_uHUAAAAJ&view_op=list_works&sortby=pubdate|Google Scholar]], [[https://orcid.org/0000-0003-1921-1433|ORCID]] or [[https://loop.frontiersin.org/people/390560/overview|LOOP]]
 \\
-===== Biarticular muscles are most responsive to upper-body pitch perturbations in human standing =====
-Our latest publication features the results of [[http://lauflabor.ifs-tud.de/doku.php?id=lab_members:lab_members_christian_schumacher|Christian]]'s lab visit in the [[http://dbl.tudelft.nl/|Delft Biorobotics Lab]]. The study investigates important muscle groups to maintain an upright body posture when being perturbed. For this purpose, he used a novel type of balance perturbation, a control moment gyroscope (see Figure) that exerts a torque on the subject's upper body. Find more information in the published paper: [[https://www.nature.com/articles/s41598-019-50995-3|Link to Scientific Reports]].
-{{ :gyro.jpg?nolink&600|[[https://www.nature.com/articles/s41598-019-50995-3|Link to Scientific Reports]] }}
-**Abstract:**
-Balancing the upper body is pivotal for upright and efficient gait. While models have identified potentially useful characteristics of biarticular thigh muscles for postural control of the upper body, experimental evidence for their specific role is lacking. Based on theoretical findings, we hypothesised that biarticular muscle activity would increase strongly in response to upper-body perturbations. To test this hypothesis, we used a novel Angular Momentum Perturbator (AMP) that, in contrast to existing methods, perturbs the upper-body posture with only minimal effect on Centre of Mass (CoM) excursions. The impulse-like AMP torques applied to the trunk of subjects resulted in upper-body pitch deflections of up to 17° with only small CoM excursions below 2 cm. Biarticular thigh muscles (biceps femoris long head and rectus femoris) showed the strongest increase in muscular activity (mid- and long-latency reflexes, starting 100 ms after perturbation onset) of all eight measured leg muscles which highlights the importance of biarticular muscles for restoring upper-body balance. These insights could be used for improving technological aids like rehabilitation or assistive devices, and the effectiveness of physical training for fall prevention e.g. for elderly people.
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