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Abstract Existing models of human walking use low-level reflexes or neural oscillators to generate movement. While appropriate to generate the stable, rhythmic movement patterns of steady-state walking, these models lack the ability to change their movement patterns or spontaneously generate new movements in the specific, goal-directed way characteristic of voluntary movements. Here we present a neuromuscular model of human locomotion that bridges this gap and combines the ability to execute goal directed movements with the generation of stable, rhythmic movement patterns that are required for robust locomotion. The model represents goals for voluntary movements of the swing leg on the task level of swing leg joint kinematics. Smooth movements plans towards the goal configuration are generated on the task level and transformed into descending motor commands that execute the planned movements, using internal models. The movement goals and plans are updated in real time based on sensory feedback and task constraints. On the spinal level, the descending commands during the swing phase are integrated with a generic stretch reflex for each muscle. Stance leg control solely relies on dedicated spinal reflex pathways. Spinal reflexes stimulate Hill-type muscles that actuate a biomechanical model with eight internal joints and six free-body degrees of freedom. The model is able to generate voluntary, goal-directed reaching movements with the swing leg and combine multiple movements in a rhythmic sequence. During walking, the swing leg is moved in a goal-directed manner to a target that is updated in real-time based on sensory feedback to maintain upright balance, while the stance leg is stabilized by low-level reflexes and a behavioral organization switching between swing and stance control for each leg. With this combination of reflex-based stance leg and voluntary, goal-directed control of the swing leg, the model controller generates rhythmic, stable walking patterns in which the swing leg movement can be flexibly updated in real-time to step over or around obstacles.
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Neural Control Principles: Bernstein’s Insights from Biomechanics of Human Movement
This chapter reviews major principles of neural control of movement proposed by N. A. Bernstein based on his biomechanical studies of human movements and published in his 1947 book ‘On Construction of Movements’. These principles include the hierarchical organization of the motor control system; synergistic sensorimotor control; the principle of sensory corrections, and the principles of repetition without repetition and fixating and subsequent releasing kinematic degrees of freedom during motor skill acquisition. These principles simplify control of the musculoskeletal system with redundant degrees of freedom and unpredictable effects of reactive and muscle forces arising in multi-segment kinematic chains. We also discuss the relevant contemporary research that has been inspired by and further developed Bernstein’s ideas. We demonstrate, in particular, examples of complex muscle and kinematic synergies organized by different levels of the motor control system, consequences of loss of proprioceptive sensory corrections on movement coordination, and emergence of economical and stable kinematic and muscle invariant movement characteristics in the process of skill acquisition by trials and errors. We conclude this chapter with motor control related parables told by N. A. Bernstein to one of the authors (VMZ).
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- Award ID(s):
- 2024414
- PAR ID:
- 10233849
- Editor(s):
- Latash, Mark L.
- Date Published:
- Journal Name:
- Bernstein's Construction of Movements: The Original Text and Commentaries
- Page Range / eLocation ID:
- 272-285
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.4324/9780367816797
