Universität zu Köln

von Twickel, Arndt, Guschlbauer, Christoph, Hooper, Scott L. and Bueschges, Ansgar (2019). Swing Velocity Profiles of Small Limbs Can Arise from Transient Passive Torques of the Antagonist Muscle Alone. Curr. Biol., 29 (1). S. 1 - 20. CAMBRIDGE: CELL PRESS. ISSN 1879-0445

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Abstract

In large limbs, changing motor neuron activity typically controls within-movement velocity. For example, sequential agonist-antagonist-agonist motor neuron firing typically underlies the slowing often present at the end of human reaches. In physiological movements of large limbs, antagonistic muscle passive torque is generally negligible. In small limbs, alternatively, passive torques can determine limb rest position, generate restoring movements to it, and decrease agonist-generated movement amplitude and velocity maxima. These observations suggest that, in small limbs, passive forces might also control velocity changes within movements. We investigated this issue in stick insect middle leg femur-tibia (FT) joint. During swing, the FT joint extensor muscle actively shortens and the flexor muscle passively lengthens. As in human reaching, after its initial acceleration, FT joint velocity continuously decreases. We measured flexor passive forces during imposed stretches spanning the ranges of FT joint angles, angular velocities, and movement amplitudes present in leg swings. The viscoelastic transient passive force that occurs during and soon after stretch depended on all three variables and could be tens of times larger than the steady-state passive force commonly measured long after stretch end. We combined these data, the flexor and extensor moment arms, and an existing extensor model to simulate FT joint swing. To measure only passive (flexor) muscle-dependent effects, we used constant extensor activations in these simulations. In simulations using data from ten flexor muscles, flexor passive torque could always produce swings with, after swing initiation, continuously decreasing velocities. Antagonist muscle passive torques alone can thus control within-movement velocity.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code von Twickel, Arndt UNSPECIFIED UNSPECIFIED UNSPECIFIED Guschlbauer, Christoph UNSPECIFIED UNSPECIFIED UNSPECIFIED Hooper, Scott L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bueschges, Ansgar UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-159452
DOI:	10.1016/j.cub.2018.11.016
Journal or Publication Title:	Curr. Biol.
Volume:	29
Number:	1
Page Range:	S. 1 - 20
Date:	2019
Publisher:	CELL PRESS
Place of Publication:	CAMBRIDGE
ISSN:	1879-0445
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOTOR-NEURON ACTIVITY; STICK INSECT; BIOMECHANICAL PROPERTIES; ACTIVITY PATTERNS; SKELETAL-MUSCLE; FORCES; WALKING; LEG; MOVEMENT; MODEL Multiple languages Biochemistry & Molecular Biology; Biology; Cell Biology Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15945