Ankle and hip postural strategies defined by joint torques

Runge, C. Ford; Shupert, Charlotte L.; Horak, Fay B.; Zajac, Felix E.

doi:10.1016/s0966-6362(99)00032-6

Cited by 500 publications

(380 citation statements)

References 18 publications

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“…A transfer of postural control synergy for the thigh has been reported as more beneficial to optimise postural stability [35]. The results obtained as to CoP parameters support this finding as they demonstrate higher performance and efficiency of compensatory responses after prolonged WUS.…”

Section: Influence On Muscle Activity At the Individual Muscle Levelsupporting

confidence: 57%

Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

et al. 2014

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Purpose: This study investigated the influence of long-term wearing of unstable shoes (WUS) on compensatory postural adjustments (CPA) to an external perturbation.Methods: Participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8 weeks. The ground reaction force signal was used to calculate the anterior-posterior (AP) displacement of the centre of pressure (CoP) and the electromyographic signal of gastrocnemius medialis (GM), tibialis anterior (TA), rectus femoris (RF) and biceps femoris (BF) muscles was used to assess individual muscle activity, antagonist co-activation and reciprocal activation at the joint (TA/GM and RF/(BF+GM) pairs) and muscle group levels (ventral (TA+RF)/dorsal (GM+BF) pair) within time intervals typical for CPA. The electromyographic signal was also used to assess muscle latency. The variables described were evaluated before and after the 8-week period while wearing the unstable shoes and barefoot. Results: Long-term WUS led to: an increase of BF activity in both conditions (barefoot and wearing the unstable shoes); a decrease of GM activity; an increase of antagonist co-activation and a decrease of reciprocal activation level at the TA/GM and ventral/dorsal pairs in the unstable shoe condition. Additionally, WUS led to a decrease in CoP displacement. However, no differences were observed in muscle onset and offset. Conclusion: Results suggest that the prolonged use of unstable shoes leads to increased ankle and muscle groups' antagonist co-activation levels and higher performance by the postural control system.

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Section: Influence On Muscle Activity At the Individual Muscle Levelsupporting

confidence: 57%

Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

et al. 2014

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“…Alexandrov et al (2001) showed that, during the same translation of the center of mass (COM; 1 cm in 500 ms), the A-eigenmovement was associated with an almost four times larger COP excursion than the H-eigenmovement (6.5 cm as compared to 1.7 cm). On the other hand, due to the difference in the inertial properties of the body segments (see Alexandrov et al, 2001), the A-eigenmovement is more efficient for slow motions, while the H-eigenmovement is more efficient for fast COM motions (see also Horak and Nashner, 1986;Runge et al, 1999).…”

Section: Composition Of Muscle Modesmentioning

confidence: 99%

Multi-muscle synergies in an unusual postural task: quick shear force production

2008

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We considered a hypothetical two-level hierarchy participating in the control of vertical posture. The framework of the uncontrolled manifold (UCM) hypothesis was used to explore the muscle groupings (M-modes) and multi-M-mode synergies involved in stabilization of a time profile of the shear force in the anterior-posterior direction. Standing subjects were asked to produce pulses of shear force into a target using visual feedback while trying to minimize the shift of the center of pressure (COP). Principal component analysis applied to integrated muscle activation indices identified three Mmodes. The composition of the M-modes was similar across subjects and the two directions of the shear force pulse. It differed from the composition of M-modes described in earlier studies of more natural actions associated with large COP shifts. Further, the trial-to-trial M-mode variance was partitioned into two components: one component that does not affect a particular performance variable (V UCM ), and its orthogonal component (V ORT ). We argued that there is a multi-M-mode synergy stabilizing this particular performance variable if V UCM is higher than V ORT . Overall, we found a multi-M-mode synergy stabilizing both shear force and COP coordinate. For the shear force, this synergy was strong for the backward force pulses and non significant for the forward pulses. An opposite result was found for the COP coordinate: the synergy was stronger for the forward force pulses. The study shows that M-mode composition can change in a task-specific way and that two different performance variables can be stabilized using the same set of elemental variables (Mmodes). The different dependences of the ΔV indices for the shear force and COP coordinate on the force pulse direction supports applicability of the principle of superposition (separate controllers for different performance variables) to the control of different mechanical variables in postural tasks. The M-mode composition allows a natural mechanical interpretation.

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“…The ankle strategy assumes that the body's COM is repositioned by moving the whole body as a single-segment, inverted pendulum, about the ankle joints, either by controlling ankle muscle stiffness or by increasing ankle muscle activity and changing the "muscle-spring" offset position (Nashner and McCollum 1985;Horak et al 1990;Winter et al 1996Winter et al , 1998Morasso and Sanguinetti 2002). The hip strategy involves antiphasic motion about both the ankle and hip joints (Nashner and McCollum 1985;Horak et al 1990;Winter et al 1996Winter et al , 1998Runge et al 1999). Extensions of these strategies include a mixed hip-ankle strategy (Kuo and Zajak 1993;Kuo 1995).…”

Section: Arm Movements and Trunk Motionmentioning

confidence: 99%

The influence of artificially increased hip and trunk stiffness on balance control in man

et al. 2004

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Lightweight corsets were used to produce midbody stiffening, rendering the hip and trunk joints practically inflexible. To examine the effect of this artificially increased stiffness on balance control, we perturbed the upright stance of young subjects (20-34 years of age) while they wore one of two types of corset or no corset at all. One type, the "half-corset", only increased hip stiffness, and the other, the "full-corset", increased stiffness of the hips and trunk. The perturbations consisted of combined roll and pitch rotations of the support surface (7.5 deg, 60 deg/s) in one of six different directions. Outcome measures were biomechanical responses of the legs, trunk, arms and head, and electromyographic (EMG) responses from leg, trunk, and upper arm muscles. With the full-corset, a decrease in forward stabilising trunk pitch rotation compared to the no-corset condition occurred for backward pitch tilts of the support surface. In contrast, the half-corset condition yielded increased forward trunk motion. Trunk backward pitch motion after forwards support-surface perturbations was the same for all corset conditions. Ankle torques and lower leg angle changes in the pitch direction were decreased for both corset conditions for forward pitch tilts of the support-surface but unaltered for backward tilts. Changes in trunk roll motion with increased stiffness were profound. After onset of a roll support-surface perturbation, the trunk rolled in the opposite direction to the support-surface tilt for the no-corset and half-corset conditions, but in the same direction as the tilt for the full-corset condition. Initial head roll angular accelerations (at 100 ms) were larger for the full-corset condition but in the same direction (opposite platform tilt) for all conditions. Arm roll movements were initially in the same direction as trunk movements, and were followed by large compensatory arm movements only for the full-corset condition. Leg muscle (soleus, peroneus longus, but not tibialis anterior) balance-correcting responses were reduced for roll and pitch tilts under both corset conditions. Responses in paraspinals were also reduced. These results indicate that young healthy normals cannot rapidly modify movement strategies sufficiently to account for changes in link flexibility following increases in hip and trunk stiffness. The changes in leg and trunk muscle responses failed to achieve a normal roll or pitch trunk end position at 700 ms (except for forward tilt rotations), even though head accelerations and trunk joint proprioception seemed to provide information on changed trunk movement profiles over the first 300 ms following the perturbation. The major adaptation to stiffness involved increased use of arm movements to regain stability. The major differences in trunk motion for the no-corset, half-corset and fullcorset conditions support the concept of a multi-link pendulum with different control dynamics in the pitch and roll planes as a model of human stance. Stiffening of the hip and trunk incre...

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Ankle and hip postural strategies defined by joint torques

Cited by 500 publications

References 18 publications

Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

Influence of long-term wearing of unstable shoes on compensatory control of posture: An electromyography-based analysis

Multi-muscle synergies in an unusual postural task: quick shear force production

The influence of artificially increased hip and trunk stiffness on balance control in man

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