Correlations of pelvis state to foot placement do not imply within-step active control

Patil, Navendu S.; Dingwell, Jonathan B.; Cusumano, Joseph P.

doi:10.1016/j.jbiomech.2019.109375

Cited by 24 publications

(30 citation statements)

References 36 publications

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“…Whether foot placement emerges mainly from a passive rather than an active mechanism is currently under debate [ 14 ], though there is increasing evidence for the latter. An illusory perturbation of the CoM state by manipulating muscle spindle afference has been reported to lead to predictable adjustments in foot placement, which indicates it to be affected by sensory input [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

et al. 2020

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Step-by-step foot placement control, relative to the center of mass (CoM) kinematic state, is generally considered a dominant mechanism for maintenance of gait stability. By adequate (mediolateral) positioning of the center of pressure with respect to the CoM, the ground reaction force generates a moment that prevents falling. In healthy individuals, foot placement is complemented mainly by ankle moment control ensuring stability. To evaluate possible compensatory relationships between step-by-step foot placement and complementary ankle moments, we investigated the degree of (active) foot placement control during steady-state walking, and under either foot placement-, or ankle moment constraints. Thirty healthy participants walked on a treadmill, while full-body kinematics, ground reaction forces and EMG activities were recorded. As a replication of earlier findings, we first showed step-by-step foot placement is associated with preceding CoM state and hip ab-/adductor activity during steady-state walking. Tight control of foot placement appears to be important at normal walking speed because there was a limited change in the degree of foot placement control despite the presence of a foot placement constraint. At slow speed, the degree of foot placement control decreased substantially, suggesting that tight control of foot placement is less essential when walking slowly. Step-by-step foot placement control was not tightened to compensate for constrained ankle moments. Instead compensation was achieved through increases in step width and stride frequency.

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Section: Introductionmentioning

confidence: 99%

Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

et al. 2020

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“…segment inertial properties) likely play an important role, as simply allowing the stance leg and torso to act as an inverted pendulum could contribute to the observed relationship. Recent 2-dimensional simulations have demonstrated that in the sagittal plane, passive dynamics can produce significant correlations between pelvis motion and step length without need for active control 5 . While similar 3-dimensional simulations require active control to ensure frontal plane gait stability 6,7 , passive dynamics surely contributes to frontal plane motion.…”

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confidence: 99%

Altered active control of step width in response to mediolateral leg perturbations while walking

Reimold

Knapp

Henderson

et al. 2020

Sci Rep

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During human walking, step width is predicted by mediolateral motion of the pelvis, a relationship that can be attributed to a combination of passive body dynamics and active sensorimotor control. The purpose of the present study was to investigate whether humans modulate the active control of step width in response to a novel mechanical environment. Participants were repeatedly exposed to a force-field that either assisted or perturbed the normal relationship between pelvis motion and step width, separated by washout periods to detect the presence of potential after-effects. As intended, force-field assistance directly strengthened the relationship between pelvis displacement and step width. This relationship remained strengthened with repeated exposure to assistance, and returned to baseline afterward, providing minimal evidence for assistance-driven changes in active control. In contrast, force-field perturbations directly weakened the relationship between pelvis motion and step width. Repeated exposure to perturbations diminished this negative direct effect, and produced larger positive after-effects once the perturbations ceased. These results demonstrate that targeted perturbations can cause humans to adjust the active control that contributes to fluctuations in step width.

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“…Its error (unexplained variance) can be attributed to mere motor noise or relaxed control. Despite the growing body of literature supporting an active contribution to the coupling between the CoM state and foot placement 1,13,14 , passive dynamics also contribute to this coupling 15 . In fact, initiating the swing phase CoM trajectory to minimize active control, and relying mostly on the body's intrinsic dynamics, could arguably be energetically efficient [16][17][18] .…”

Section: Introductionmentioning

confidence: 99%

Ankle muscles drive mediolateral center of pressure control to ensure stable steady state gait

Leeuwen

Dieën

Daffertshofer

et al. 2021

Preprint

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During steady-state walking mediolateral gait stability can be maintained by controlling the center of pressure (CoP). The CoP modulates the moment of the ground reaction force, which brakes and reverses movement of the center of mass (CoM) towards the lateral border of the base of support. In addition to foot placement, ankle moments serve to control the CoP. We hypothesized that, during steady-state walking, single stance ankle moments establish a CoP shift to correct for errors in foot placement. We expected ankle muscle activity to be associated with this complementary CoP shift. During treadmill walking, full-body kinematics, ground reaction forces and electromyography were recorded in thirty healthy participants. We found a negative relationship between preceding foot placement error and CoP displacement during single stance. Too medial steps were compensated for by a lateral CoP shift and vice versa, too lateral steps were compensated for by a medial CoP shift. Peroneus longus, soleus and tibialis anterior activity correlated with these CoP shifts. As such, we identified an (active) ankle strategy during steady-state walking. As expected, absolute explained CoP variance by foot placement error decreased when walking with shoes constraining ankle moments. Yet, contrary to our expectations that ankle moment control would compensate for constrained foot placement, the absolute explained CoP variance by foot placement error did not increase when foot placement was constrained. We argue that this lack of compensation reflects the interdependent nature of ankle moment and foot placement control. We suggest that single stance ankle moments do not only compensate for preceding foot placement errors, but also assist control of the subsequent foot placement. Foot placement and ankle moment control are caught in a circular relationship, in which constraints imposed on one will also influence the other.

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Correlations of pelvis state to foot placement do not imply within-step active control

Cited by 24 publications

References 36 publications

Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

Altered active control of step width in response to mediolateral leg perturbations while walking

Ankle muscles drive mediolateral center of pressure control to ensure stable steady state gait

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