scholarly journals Force dynamics and synergist muscle activation in stick insects: the effects of using joint torques as mechanical stimuli

2018 ◽  
Vol 120 (4) ◽  
pp. 1807-1823 ◽  
Author(s):  
Sasha N. Zill ◽  
Chris J. Dallmann ◽  
Ansgar Büschges ◽  
Sumaiya Chaudhry ◽  
Josef Schmitz
Keyword(s):  
Muscle Activation ◽  
Force Feedback ◽  
Inverse Dynamics ◽  
Muscle Synergies ◽  
Mechanical Stimuli ◽  
Flexor Muscle ◽  
Joint Torques ◽  
Force Dynamics ◽  
Stick Insects ◽  
Depressor Muscle

Many sensory systems are tuned to specific parameters of behaviors and have effects that are task-specific. We have studied how force feedback contributes to activation of synergist muscles in serially homologous legs of stick insects. Forces were applied using conventional half-sine or ramp and hold functions. We also utilized waveforms of joint torques calculated from experiments in freely walking animals. In all legs, forces applied to either the tarsus (foot) or proximal leg segment (trochanter) activated synergist muscles that generate substrate grip and support, but coupling of the depressor muscle to tarsal forces was weak in the front legs. Activation of trochanteral receptors using ramp and hold functions generated positive feedback to the depressor muscle in all legs when animals were induced to seek substrate grip. However, discharges of the synergist flexor muscle showed adaptation at moderate force levels. In contrast, application of forces using torque waveforms, which do not have a static hold phase, produced sustained discharges in muscle synergies with little adaptation. Firing frequencies reflected the magnitude of ground reaction forces, were graded to changes in force amplitude, and could also be modulated by transient force perturbations added to the waveforms. Comparison of synergist activation by torques and ramp and hold functions revealed a strong influence of force dynamics (dF/d t). These studies support the idea that force receptors can act to tune muscle synergies synchronously to the range of force magnitudes and dynamics that occur in each leg according to their specific use in behavior. NEW & NOTEWORTHY The effects of force receptors (campaniform sensilla) on leg muscles and synergies were characterized in stick insects using both ramp and hold functions and waveforms of joint torques calculated by inverse dynamics. Motor responses were sustained and showed reduced adaptation to the more “natural” and nonlinear torque stimuli. Calculation of the first derivative (dF/d t) of the torque waveforms demonstrated that this difference was correlated with the dynamic sensitivities of the system.

scholarly journals Modularity speeds up motor learning by overcoming mechanical bias in musculoskeletal geometry

2018 ◽  
Vol 15 (147) ◽  
pp. 20180249 ◽  
Author(s):  
Shota Hagio ◽  
Motoki Kouzaki
Keyword(s):  
Cortical Neurons ◽  
Muscle Activation ◽  
Primary Motor Cortex ◽  
Neuromuscular Control ◽  
Muscle Synergies ◽  
Model Learning ◽  
Joint Torques ◽  
Muscle Activation Patterns ◽  
Wide Range ◽  
Simple Neural Network

We can easily learn and perform a variety of movements that fundamentally require complex neuromuscular control. Many empirical findings have demonstrated that a wide range of complex muscle activation patterns could be well captured by the combination of a few functional modules, the so-called muscle synergies. Modularity represented by muscle synergies would simplify the control of a redundant neuromuscular system. However, how the reduction of neuromuscular redundancy through a modular controller contributes to sensorimotor learning remains unclear. To clarify such roles, we constructed a simple neural network model of the motor control system that included three intermediate layers representing neurons in the primary motor cortex, spinal interneurons organized into modules and motoneurons controlling upper-arm muscles. After a model learning period to generate the desired shoulder and/or elbow joint torques, we compared the adaptation to a novel rotational perturbation between modular and non-modular models. A series of simulations demonstrated that the modules reduced the effect of the bias in the distribution of muscle pulling directions, as well as in the distribution of torques associated with individual cortical neurons, which led to a more rapid adaptation to multi-directional force generation. These results suggest that modularity is crucial not only for reducing musculoskeletal redundancy but also for overcoming mechanical bias due to the musculoskeletal geometry allowing for faster adaptation to certain external environments.

Reducing Metabolic Cost During Planetary Ambulation Using Robotic Actuation

2021 ◽  
Vol 92 (7) ◽  
pp. 570-578
Author(s):  
Logan Kluis ◽  
Nathan Keller ◽  
Hedan Bai ◽  
Narahari Iyengar ◽  
Robert Shepherd ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Inverse Dynamics ◽  
Metabolic Cost ◽  
Biomechanical Analysis ◽  
Lower Body ◽  
Extravehicular Activity ◽  
Joint Torques ◽  
Activity Performance ◽  
Human Joints ◽  
Body Joints

INTRODUCTION: Current spacesuits are cumbersome and metabolically expensive. The use of robotic actuators could improve extravehicular activity performance. We propose a novel method to quantify the benefit of robotic actuators during planetary ambulation.METHODS: Using the OpenSim framework, we completed a biomechanical analysis of three walking conditions: unsuited, suited with the extravehicular mobility unit (EMU) spacesuit (represented as external joint torques applied to human joints), and suited with the EMU and assisted by robotic actuators capable of producing up to 10 Nm of torque. For each scenario, we calculated the inverse kinematics and inverse dynamics of the lower body joints (hip, knee, and ankle). We also determined the activation of muscles and robotic actuators (when present). Finally, from inverse dynamics and muscle activation results, the metabolic cost of one gait cycle was calculated in all three conditions.RESULTS: The moments of lower body joints increased due to the increased resistance to movement from the spacesuit. The additional torque increased the overall metabolic cost by 85 compared to the unsuited condition. The assistive robotic actuators were able to reduce the metabolic cost induced by EMU resistance by 15.DISCUSSION: Our model indicates that the majority of metabolic cost reduction can be attributed to the actuators located at the hip. The robotic actuators reduced metabolic cost similar to that of modern-day actuators used to improve walking. During a Mars mission, the actuators could save one crewmember up to 100,000 kilocal on one 539-d planetary expedition.Kluis L, Keller N, Bai H, Iyengar N, Shepherd R, Diaz-Artiles A. Reducing metabolic cost during planetary ambulation using robotic actuation. Aerosp Med Hum Perform. 2021; 92(7):570578.

scholarly journals Evaluation of force feedback in walking using joint torques as 'naturalistic' stimuli

2021 ◽  
Author(s):  
Sasha N. Zill ◽  
Chris J Dallmann ◽  
Nicholas Szczecinski ◽  
Ansgar Büschges ◽  
Josef Schmitz
Keyword(s):  
Force Feedback ◽  
Firing Frequency ◽  
Joint Torques ◽  
Stick Insects ◽  
Motor Activities ◽  
Reaction Forces ◽  
Body Load ◽  
Vertical Ground ◽  
Horizontal Substrate ◽  
Vertical Ground Reaction Forces

Control of adaptive walking requires the integration of sensory signals of muscle force and load. We have studied how mechanoreceptors (tibial campaniform sensilla) encode 'naturalistic' stimuli derived from joint torques of stick insects walking on a horizontal substrate. Previous studies showed that forces applied to the legs using the mean torque profiles of a proximal joint were highly effective in eliciting motor activities. However, substantial variations in torque direction and magnitude occurred at the more distal femoro-tibial joint, which can generate braking or propulsive forces and provide lateral stability. To determine how these forces are encoded, we utilized torque waveforms of individual steps that had maximum values in stance in the directions of flexion or extension. Analysis of kinematic data showed that the torques in different directions tended to occur in different ranges of joint angles. Variations within stance were not accompanied by comparable changes in joint angle but often reflected vertical ground reaction forces and leg support of body load. Application of torque waveforms elicited sensory discharges with variations in firing frequency similar to those seen in freely walking insects. All sensilla directionally encoded the dynamics of force increases and showed hysteresis to transient force decreases. Smaller receptors exhibited more tonic firing. Our findings suggest that dynamic sensitivity in force feedback can modulate ongoing muscle activities to stabilize distal joints when large forces are generated at proximal joints. Further, use of 'naturalistic' stimuli can reproduce characteristics seen in freely moving animals that are absent in conventional restrained preparations.

scholarly journals The role of leg touchdown for the control of locomotor activity in the walking stick insect

2015 ◽  
Vol 113 (7) ◽  
pp. 2309-2320 ◽  
Author(s):  
Joscha Schmitz ◽  
Matthias Gruhn ◽  
Ansgar Büschges
Keyword(s):  
Muscle Activation ◽  
Stance Phase ◽  
Stick Insect ◽  
Afferent Input ◽  
Flexor Muscle ◽  
Locomotor Control ◽  
Burst Intensity ◽  
Stick Insects ◽  
Additional Feedback

Much is known on how select sensory feedback contributes to the activation of different motoneuron pools in the locomotor control system of stick insects. However, even though activation of the stance phase muscles depressor trochanteris, retractor unguis, flexor tibiae and retractor coxae is correlated with the touchdown of the leg, the potential sensory basis of this correlation or its connection to burst intensity remains unknown. In our experiments, we are using a trap door setup to investigate how ground contact contributes to stance phase muscle activation and burst intensity in different stick insect species, and which afferent input is involved in the respective changes. While the magnitude of activation is changed in all of the above stance phase muscles, only the timing of the flexor tibiae muscle is changed if the animal unexpectedly steps into a hole. Individual and combined ablation of different force sensors on the leg demonstrated influence from femoral campaniform sensilla on flexor muscle timing, causing a significant increase in the latencies during control and air steps. Our results show that specific load feedback signals determine the timing of flexor tibiae activation at the swing-to-stance transition in stepping stick insects, but that additional feedback may also be involved in flexor muscle activation during stick insect locomotion. With respect to timing, all other investigated stance phase muscles appear to be under sensory control other than that elicited through touchdown.

Abdominal and hip flexor muscle activation during various training exercises

1997 ◽  
Vol 75 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Eva A. Andersson ◽  
Johnny Nilsson ◽  
Zhijia Ma ◽  
Alf Thorstensson
Keyword(s):  
Muscle Activation ◽  
Flexor Muscle ◽  
Training Exercises ◽  
Hip Flexor

Effect of neck flexor muscle activation on impact velocity of the head during backward falls in young adults

2017 ◽  
Vol 49 ◽  
pp. 28-33 ◽  
Author(s):  
W.J. Choi ◽  
S.N. Robinovitch ◽  
S.A. Ross ◽  
J. Phan ◽  
D. Cipriani
Keyword(s):  
Young Adults ◽  
Impact Velocity ◽  
Muscle Activation ◽  
Flexor Muscle

scholarly journals Lower complexity of motor primitives ensures robust control of high-speed human locomotion

2020 ◽  
Author(s):  
Alessandro Santuz ◽  
Antonis Ekizos ◽  
Yoko Kunimasa ◽  
Kota Kijima ◽  
Masaki Ishikawa ◽  
...  
Keyword(s):  
High Speed ◽  
Muscle Activation ◽  
Human Locomotion ◽  
Muscle Synergies ◽  
Activation Patterns ◽  
Motor Primitives ◽  
Muscle Activation Patterns ◽  
Relative Contribution ◽  
Muscle Activations ◽  
Low Dimensional

AbstractWalking and running are mechanically and energetically different locomotion modes. For selecting one or another, speed is a parameter of paramount importance. Yet, both are likely controlled by similar low-dimensional neuronal networks that reflect in patterned muscle activations called muscle synergies. Here, we investigated how humans synergistically activate muscles during locomotion at different submaximal and maximal speeds. We analysed the duration and complexity (or irregularity) over time of motor primitives, the temporal components of muscle synergies. We found that the challenge imposed by controlling high-speed locomotion forces the central nervous system to produce muscle activation patterns that are wider and less complex relative to the duration of the gait cycle. The motor modules, or time-independent coefficients, were redistributed as locomotion speed changed. These outcomes show that robust locomotion control at challenging speeds is achieved by modulating the relative contribution of muscle activations and producing less complex and wider control signals, whereas slow speeds allow for more irregular control.

Effect of gravity and kinematic constraints on muscle synergies in arm cycling.

2021 ◽  
Author(s):  
Lilla Botzheim ◽  
Jozsef Laczko ◽  
Diego Torricelli ◽  
Mariann Mravcsik ◽  
José L. Pons ◽  
...  
Keyword(s):  
Motor Control ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
Body Position ◽  
Medical Rehabilitation ◽  
Muscle Synergies ◽  
Muscle Coordination ◽  
Arm Cycling ◽  
Custom Made ◽  
Crank Length

Arm cycling is a bi-manual motor task used in medical rehabilitation and in sports training. Understanding how muscle coordination changes across different biomechanical constraints in arm cycling is a step towards improved rehabilitation approaches. This exploratory study aims to get new insights on motor control during arm cycling. To achieve our main goal, we used the muscle synergies analysis to test three hypotheses: 1) body position with respect to gravity (sitting and supine) has an effect on muscle synergies; 2) the movement size (crank length) has an effect on the synergistic behavior; 3) the bimanual cranking mode (asynchronous and synchronous) requires different synergistic control. Thirteen able-bodied volunteers performed arm cranking on a custom-made device with unconnected cranks, which allowed testing three different conditions: body position (sitting versus supine), crank length (10cm versus 15cm) and cranking mode (synchronous versus asynchronous). For each of the eight possible combinations, subjects cycled for 30 seconds while electromyography of 8 muscles (4 from each arm) were recorded: biceps brachii, triceps brachii, anterior deltoid and posterior deltoid. Muscle synergies in this 8-dimensional muscle space were extracted by non-negative matrix factorization. Four synergies accounted for over 90% of muscle activation variances in all conditions. Results showed that synergies were affected by body position and cranking mode but practically unaffected by movement size. These results suggest that the central nervous system may employ different motor control strategies in response to external constraints such as cranking mode and body position during arm cycling.

Estimation of Muscle Forces About the Ankle During Gait in Healthy and Neurologically Impaired Subjects

2011 ◽  
pp. 320-347
Author(s):  
Daniel N. Bassett ◽  
Joseph D. Gardinier ◽  
Kurt T. Manal ◽  
Thomas S. Buchanan
Keyword(s):  
Muscle Activation ◽  
Inverse Dynamics ◽  
Biomechanical Model ◽  
Forward Dynamics ◽  
Muscle Forces ◽  
Dynamics Model ◽  
Joint Moments ◽  
Neurologically Impaired ◽  
Model Predictions ◽  
Contraction Dynamics

This chapter describes a biomechanical model of the forces about the ankle joint applicable to both unimpaired and neurologically impaired subjects. EMGs and joint kinematics are used as inputs and muscle forces are the outputs. A hybrid modeling approach that uses both forward and inverse dynamics is employed and physiological parameters for the model are tuned for each subject using optimization procedures. The forward dynamics part of the model takes muscle activation and uses Hill-type models of muscle contraction dynamics to estimate muscle forces and the corresponding joint moments. Inverse dynamics is used to calibrate the forward dynamics model predictions of joint moments. In this chapter we will describe how to implement an EMG-driven hybrid forward and inverse dynamics model of the ankle that can be used in healthy and neurologically impaired people.

Influence of the Musculotendon Dynamics on the Muscle Force-Sharing Problem of the Shoulder—A Fully Inverse Dynamics Approach

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Quental Carlos ◽  
Azevedo Margarida ◽  
Ambrósio Jorge ◽  
Gonçalves S. B. ◽  
Folgado João
Keyword(s):  
Muscle Activation ◽  
Inverse Dynamics ◽  
Glenohumeral Joint ◽  
Inverse Dynamic ◽  
Force Sharing ◽  
Joint Reaction Forces ◽  
Reaction Forces ◽  
Muscle Activations ◽  
Joint Reaction

Abstract Most dynamic simulations are based on inverse dynamics, being the time-dependent physiological nature of the muscle properties rarely considered due to numerical challenges. Since the influence of muscle physiology on the consistency of inverse dynamics simulations remains unclear, the purpose of the present study is to evaluate the computational efficiency and biological validity of four musculotendon models that differ in the simulation of the muscle activation and contraction dynamics. Inverse dynamic analyses are performed using a spatial musculoskeletal model of the upper limb. The muscle force-sharing problem is solved for five repetitions of unloaded and loaded motions of shoulder abduction and shoulder flexion. The performance of the musculotendon models is evaluated by comparing muscle activation predictions with electromyography (EMG) signals, measured synchronously with motion for 11 muscles, and the glenohumeral joint reaction forces estimated numerically with those measured in vivo. The results show similar muscle activations for all muscle models. Overall, high cross-correlations are computed between muscle activations and the EMG signals measured for all movements analyzed, which provides confidence in the results. The glenohumeral joint reaction forces estimated compare well with those measured in vivo, but the influence of the muscle dynamics is found to be negligible. In conclusion, for slow-speed, standard movements of the upper limb, as those studied here, the activation and musculotendon contraction dynamics can be neglected in inverse dynamic analyses without compromising the prediction of muscle and joint reaction forces.

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