Determinants of postural orientation in quadrupedal stance

Fung, Joyce; Macpherson, Jane M.

doi:10.1523/jneurosci.15-02-01121.1995

Cited by 40 publications

(26 citation statements)

References 18 publications

(12 reference statements)

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“…2). Large variations in muscle activity across animals have been previously demonstrated during both quiet standing and postural responses to perturbation even though the forces produced were similar (Fung and Macpherson 1995;Torres-Oviedo et al 2006). …”

Section: Resultsmentioning

confidence: 87%

“…5), consistent with the idea that the kinematics of this self-selected posture optimize this criterion. Similarly, Fung and Macpherson (1995) used an inverse dynamic analysis to demonstrate that the preferred posture kinematics minimize total joint torques for antigravity support. At other postures, the limb is levered at the girdle, preserving the intralimb geometry and locally minimizing joint torques.…”

Section: Discussionmentioning

confidence: 99%

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Functional muscle synergies constrain force production during postural tasks

McKay

Ting

2008

Journal of Biomechanics

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We recently demonstrated that a set of five functional muscle synergies were sufficient to characterize both hindlimb muscle activity and active forces during automatic postural responses in cats standing at multiple postural configurations. This characterization depended critically upon the assumption that the endpoint force vector (synergy force vector) produced by the activation of each muscle synergy rotated with the limb axis as the hindlimb posture varied in the sagittal plane. Here, we used a detailed, 3D static model of the hindlimb to confirm that this assumption is biomechanically plausible: as we varied the model posture, simulated synergy force vectors rotated monotonically with the limb axis in the parasagittal plane (r 2 = 0.94 ± 0.08). We then tested whether a neural strategy of using these five functional muscle synergies provides the same force-generating capability as controlling each of the 31 muscles individually. We compared feasible force sets (FFS) from the model with and without a muscle synergy organization. FFS volumes were significantly reduced with the muscle synergy organization (F = 1556.01, p ≪ 0.01), and as posture varied, the synergy-limited FFSs changed in shape, consistent with changes in experimentally-measured active forces. In contrast, nominal FFS shapes were invariant with posture, reinforcing prior findings that postural forces cannot be predicted by hindlimb biomechanics alone. We propose that an internal model for postural force generation may coordinate functional muscle synergies that are invariant in intrinsic limb coordinates, and this reduced-dimension control scheme reduces the set of forces available for postural control.

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Section: Resultsmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Functional muscle synergies constrain force production during postural tasks

McKay

Ting

2008

Journal of Biomechanics

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“…During the swing phase, the front or rear end of the animal is only supported by one leg. However, maintenance of stance requires not only the support of the body against gravity but also that the COM remains within the limits of support in the horizontal plane (Fung and Macpherson, 1995). By means of a shorter t sw ′, the piglet can return more quickly to a phase where the front or rear end of the body is supported by two legs.…”

Section: Does Intralimb Coordination Change During Early Gait Developmentioning

confidence: 99%

How innate is locomotion in precocial animals? A study on the early development of spatio-temporal gait variables and gait symmetry in piglets

Hole

Goyens

Prims

et al. 2017

Journal of Experimental Biology

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Locomotion is one of the most important ecological functions in animals. Precocial animals, such as pigs, are capable of independent locomotion shortly after birth. This raises the question whether coordinated movement patterns and the underlying muscular control in these animals is fully innate or whether there still exists a rapid maturation. We addressed this question by studying gait development in neonatal pigs through the analysis of spatio-temporal gait characteristics during locomotion at self-selected speed. To this end, we made video recordings of piglets walking along a corridor at several time points (from 0 h to 96 h). After digitization of the footfalls, we analysed self-selected speed and spatio-temporal characteristics (e.g. stride and step lengths, stride frequency and duty factor) to study dynamic similarity, intralimb coordination and interlimb coordination. To assess the variability of the gait pattern, left-right asymmetry was studied. To distinguish neuromotor maturation from effects caused by growth, both absolute and normalized data (according to the dynamic similarity concept) were included in the analysis. All normalized spatiotemporal variables reached stable values within 4 h of birth, with most of them showing little change after the age of 2 h. Most asymmetry indices showed stable values, hovering around 10%, within 8 h of birth. These results indicate that coordinated movement patterns are not entirely innate, but that a rapid neuromotor maturation, potentially also the result of the rearrangement or recombination of existing motor modules, takes place in these precocial animals.

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“…Our previous study showed that during quiet stance, the angle of both the limb axis and the GRF vector changed linearly with stance distance, with the GRF vector angle having a slightly smaller gain than that of limb axis angle (Fung and Macpherson 1995). Therefore we transformed the original force data into the coordinate system of the average GRF vector that was measured during quiet standing at each stance distance, named here the F-frame (Fig.…”

Section: Synergy Force Vectors Are Consistent With Respect To the Limmentioning

confidence: 99%

“…Initial attempts to reconstruct GRF responses to platform translation using this control set of synergy W F s were successful only at reconstructing data from the preferred stance distance and not from the other distances. We attributed the difficulty in force reconstruction to the large change in GRF vector orientation that accompanies changes in stance distance.Our previous study showed that during quiet stance, the angle of both the limb axis and the GRF vector changed linearly with stance distance, with the GRF vector angle having a slightly smaller gain than that of limb axis angle (Fung and Macpherson 1995). Therefore we transformed the original force data into the coordinate system of the average GRF vector that was measured during quiet standing at each stance distance, named here the F-frame (Fig.…”

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confidence: 99%

Muscle Synergy Organization Is Robust Across a Variety of Postural Perturbations

Torres-Oviedo¹,

Macpherson²,

Ting³

2006

Journal of Neurophysiology

420

402

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. We recently showed that four muscle synergies can reproduce multiple muscle activation patterns in cats during postural responses to support surface translations. We now test the robustness of functional muscle synergies, which specify muscle groupings and the active force vectors produced during postural responses under several biomechanically distinct conditions. We aimed to determine whether such synergies represent a generalized control strategy for postural control or if they are merely specific to each postural task. Postural responses to multidirectional translations at different fore-hind paw distances and to multidirectional rotations at the preferred stance distance were analyzed. Five synergies were required to adequately reconstruct responses to translation at the preferred stance distance-four were similar to our previous analysis of translation, whereas the fifth accounted for the newly added background activity during quiet stance. These five control synergies could account for Ͼ80% total variability or r 2 Ͼ 0.6 of the electromyographic and force tuning curves for all other experimental conditions. Forces were successfully reconstructed but only when they were referenced to a coordinate system that rotated with the limb axis as stance distance changed. Finally, most of the functional muscle synergies were similar across all of the six cats in terms of muscle synergy number, synergy activation patterns, and synergy force vectors. The robustness of synergy organization across perturbation types, postures, and animals suggests that muscle synergies controlling task-variables are a general construct used by the CNS for balance control. I N T R O D U C T I O NRecent findings suggest that the CNS simplifies motor control by constraining muscles to be activated in fixed groups, or synergies, where each synergy is defined as a set of muscles recruited by a single neural command signal. Complex muscle activation patterns in a wide range of motor tasks including locomotion, finger spelling, and postural tasks, can be decomposed into the summed activation of just a few muscle synergies d'Avella et al. 2003;Ivanenko et al. 2003Ivanenko et al. , 2004Krishnamoorthy et al. 2003;Poppele and Bosco 2003;Poppele et al. 2002;Ting and Macpherson 2005;Tresch et al. 1999;Weiss and Flanders 2004). A muscle synergy control structure provides an attractive simplifying strategy for the control of complex movements because it reduces the number of output patterns that the nervous system must specify for a large number of muscles yet allows flexibility in the final expression of muscle activation.A synergy control structure not only simplifies the motor output pattern for muscle activation but may also be functionally related to high-level control parameters-global biomechanical variables that are important for movement control. For example, Ting and Macpherson (2005) demonstrated in cats that four muscle synergies could account for the spatial tuning patterns of the automatic postural response elicited by support surface ...

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Determinants of postural orientation in quadrupedal stance

Cited by 40 publications

References 18 publications

Functional muscle synergies constrain force production during postural tasks

Functional muscle synergies constrain force production during postural tasks

How innate is locomotion in precocial animals? A study on the early development of spatio-temporal gait variables and gait symmetry in piglets

Muscle Synergy Organization Is Robust Across a Variety of Postural Perturbations

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