One more time about motor (and non-motor) synergies

Latash, Mark L.

doi:10.1007/s00221-021-06188-4

Cited by 40 publications

(25 citation statements)

References 155 publications

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“…Rather, activity in the leg muscles and power at the hip and knee joints indicate active control of the forward swinging limb, which will alter the step length from what a passively swinging limb would yield (Winter, 1991). It is plausible that variations in muscle lengths from their reference values, arising from variations in push off forces, will engage spinal stretch reflexes that will alter step length and contribute to the observed MOS AP synergy (Latash, 2021). This explanation is consistent with the view that for steady state, level gait, humans rely on spinal feedback for control in the AP direction (Bauby and Kuo, 2000, Collins and Kuo, 2013).…”

Section: Discussionmentioning

confidence: 99%

Humans prioritize walking efficiency or walking stability based on environmental risk

Kulkarni

Cui

Rietdyk

et al. 2022

Preprint

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During steady-state gait, the instantaneous passive dynamics, quantified using the margin of stability in the anterior-posterior (AP) direction (MOSAP), are unstable. Although the instability indicates that substantial control will be required to reject a perturbation, the instability also allows for forward progression with low energy expenditure when the gait is unperturbed. Here, we examined whether humans control MOSAP to exploit the passive dynamics, and whether they adjust MOSAP when the threat to AP balance is increased. We computed MOSAP for six consecutive steps when healthy young adults performed unobstructed gait trials, and when they approached and crossed an obstacle. Uncontrolled manifold analysis indicated that the extrapolated center of mass and step length co-varied to maintain MOSAP for all steps during unobstructed and obstructed gait. Furthermore, the MOSAP values indicated unstable passive dynamics for all steps except while crossing the obstacle with the leading limb. Based on these results, we concluded that the MOSAP is controlled to exploit the passive dynamics and achieve forward progression at low energetic cost. Finally, MOSAP increased (indicating more stable dynamics) while approaching and crossing the obstacle with the leading limb, and then declined for later steps, indicating a fluid tradeoff between stability and energy efficiency.

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Section: Discussionmentioning

confidence: 99%

Humans prioritize walking efficiency or walking stability based on environmental risk

Kulkarni

Cui

Rietdyk

et al. 2022

Preprint

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“…For example, the numerous leg muscles can be organized to stabilize the coordinate of the center of pressure during standing, or the vertical force applied to the body during hopping, or the horizontal foot trajectory during kicking a ball, and so forth. The framework of the UCM hypothesis is readily compatible with the principle of abundance (reviewed in Latash, 2008Latash, , 2021aLatash, , 2021b.…”

Section: Bernstein's Definition Of Synergiesmentioning

confidence: 99%

“…reviews have addressed this topic explicitly accepting or implying various definitions of synergies (Bruton & O'Dwyer, 2018;Latash, 2008Latash, , 2021bLatash et al, 2007;Tresch & Jarc, 2009;Turvey, 2007). In this review, we follow the traditions of Nikolai Bernstein and accept his view on synergies described in detail in his classical book On the Construction of Movements (Bernstein, 1947;translation in Latash, 2020a).…”

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confidence: 99%

Intramuscle Synergies: Their Place in the Neural Control Hierarchy

2023

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We accept a definition of synergy introduced by Nikolai Bernstein and develop it for various actions, from those involving the whole body to those involving a single muscle. Furthermore, we use two major theoretical developments in the field of motor control—the idea of hierarchical control with spatial referent coordinates and the uncontrolled manifold hypothesis—to discuss recent studies of synergies within spaces of individual motor units (MUs) recorded within a single muscle. During the accurate finger force production tasks, MUs within hand extrinsic muscles form robust groups, with parallel scaling of the firing frequencies. The loading factors at individual MUs within each of the two main groups link them to the reciprocal and coactivation commands. Furthermore, groups are recruited in a task-specific way with gains that covary to stabilize muscle force. Such force-stabilizing synergies are seen in MUs recorded in the agonist and antagonist muscles but not in the spaces of MUs combined over the two muscles. These observations reflect inherent trade-offs between synergies at different levels of a control hierarchy. MU-based synergies do not show effects of hand dominance, whereas such effects are seen in multifinger synergies. Involuntary, reflex-based, force changes are stabilized by intramuscle synergies but not by multifinger synergies. These observations suggest that multifinger (multimuscle synergies) are based primarily on supraspinal circuitry, whereas intramuscle synergies reflect spinal circuitry. Studies of intra- and multimuscle synergies promise a powerful tool for exploring changes in spinal and supraspinal circuitry across patient populations.

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“…Of note, wearable solutions (eventually complemented, in some cases, by cost considerations) tend to discourage the usage of many sensors mounted on the body, which could negatively impact the form factor and the wearability of the device [ 18 ]. A possible approach to tackle this issue is to exploit the covariation schemes between functional elements or DoFs of our body, usually named as motor synergies [ 19 ]. Indeed, several works demonstrated the existence of correlation patterns between different joints and/or muscles in the upper [ 20 , 21 , 22 , 23 ] and lower limb [ 24 , 25 ].…”

Section: Introductionmentioning

confidence: 99%

A Multi-Modal Under-Sensorized Wearable System for Optimal Kinematic and Muscular Tracking of Human Upper Limb Motion

Paolo

Baracca

Menolotto

et al. 2023

Sensors

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Wearable sensing solutions have emerged as a promising paradigm for monitoring human musculoskeletal state in an unobtrusive way. To increase the deployability of these systems, considerations related to cost reduction and enhanced form factor and wearability tend to discourage the number of sensors in use. In our previous work, we provided a theoretical solution to the problem of jointly reconstructing the entire muscular-kinematic state of the upper limb, when only a limited amount of optimally retrieved sensory data are available. However, the effective implementation of these methods in a physical, under-sensorized wearable has never been attempted before. In this work, we propose to bridge this gap by presenting an under-sensorized system based on inertial measurement units (IMUs) and surface electromyography (sEMG) electrodes for the reconstruction of the upper limb musculoskeletal state, focusing on the minimization of the sensors’ number. We found that, relying on two IMUs only and eight sEMG sensors, we can conjointly reconstruct all 17 degrees of freedom (five joints, twelve muscles) of the upper limb musculoskeletal state, yielding a median normalized RMS error of 8.5% on the non-measured joints and 2.5% on the non-measured muscles.

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One more time about motor (and non-motor) synergies

Cited by 40 publications

References 155 publications

Humans prioritize walking efficiency or walking stability based on environmental risk

Humans prioritize walking efficiency or walking stability based on environmental risk

Intramuscle Synergies: Their Place in the Neural Control Hierarchy

A Multi-Modal Under-Sensorized Wearable System for Optimal Kinematic and Muscular Tracking of Human Upper Limb Motion

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