Predicting multiple step placements for human balance recovery tasks

Aftab, Zohaib; Thomas, Robert; Wieber, Pierre-Brice

doi:10.1016/j.jbiomech.2012.08.038

Cited by 16 publications

(13 citation statements)

References 32 publications

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“…the priority is given to zeroing the CoM’s velocity), has a very small effect on the balance recovery behavior. This point was already shown in one of our previous study [ 29 ].…”

Section: Resultssupporting

confidence: 84%

“…However, in most of the previous models involving recovery stepping, the step duration is either neglected (instantaneous stepping as in [ 18 ]) or is considered known and pre-fixed (e.g. [ 17 , 29 ]) to simplify the model. Indeed, including step duration as an optimization variable renders the optimization scheme non-linear, requiring specialized non-linear MPC solvers [ 38 ].…”

Section: Discussionmentioning

confidence: 99%

“…Keeping this in view, we previously proposed a balance recovery model which could predict single and multiple stepping responses [ 29 ] based on the Model Predictive Control (MPC) approach. This approach is inspired from the prediction capability of human where the balance recovery actions are decided based on the rough estimation of system’s state evolution.…”

Section: Introductionmentioning

confidence: 99%

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Balance Recovery Prediction with Multiple Strategies for Standing Humans

2016

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Human balance recovery from external disturbances is a complex process, and simulating it remains an open challenge. In particular, there still is a need for a comprehensive numerical tool capable of predicting the outcome of a balance perturbation, including in particular the three elementary recovery strategies: ankle, hip and stepping with variable step duration. In order to fill this gap we further developed a previously proposed multiple step balance recovery prediction tool to include the use of the hip strategy and variable step duration. Simulated recovery reactions are compared against observations from different experimental situations from the literature. Reasonable accuracy in terms of step positions and durations were obtained for these different situations using a single set of controller parameters. Moreover, variations in the use of the hip strategy and the step duration between situations were consistent with biomechanical observations. Such a model could be useful to better understand the balance recovery mechanisms, and could also be used to identify potentially hazardous situations.

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“…the priority is given to zeroing the CoM’s velocity), has a very small effect on the balance recovery behavior. This point was already shown in one of our previous study [ 29 ].…”

Section: Resultssupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Balance Recovery Prediction with Multiple Strategies for Standing Humans

2016

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“…, ; Brenière and Do ; Pai and Patton ; Aftab et al. ). In GI, we asked subjects to initiate gait keeping step length constant (Brenière and Do ; MacDougall and Moore ) in different trials, performed at slow, spontaneous, or fast velocity.…”

Section: Discussionmentioning

confidence: 99%

“…; Pai and Patton ; Aftab et al. ). Asking subjects to vary step length, without changing the initial inclination, should modulate the duration of triceps surae activity accordingly.…”

Section: Introductionmentioning

confidence: 99%

By counteracting gravity, triceps surae sets both kinematics and kinetics of gait

et al. 2014

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In the single‐stance phase of gait, gravity acting on the center of mass (CoM) causes a disequilibrium torque, which generates propulsive force. Triceps surae activity resists gravity by restraining forward tibial rotation thereby tuning CoM momentum. We hypothesized that time and amplitude modulation of triceps surae activity determines the kinematics (step length and cadence) and kinetics of gait. Nineteen young subjects participated in two experiments. In the gait initiation (GI) protocol, subjects deliberately initiated walking at different velocities for the same step length. In the balance‐recovery (BR) protocol, subjects executed steps of different length after being unexpectedly released from an inclined posture. Ground reaction force was recorded by a large force platform and electromyography of soleus, gastrocnemius medialis and lateralis, and tibialis anterior muscles was collected by wireless surface electrodes. In both protocols, the duration of triceps activity was highly correlated with single‐stance duration (GI, R2 = 0.68; BR, R2 = 0.91). In turn, step length was highly correlated with single‐stance duration (BR, R2 = 0.70). Control of CoM momentum was obtained by decelerating the CoM fall via modulation of amplitude of triceps activity. By modulation of triceps activity, the central nervous system (CNS) varied the position of CoM with respect to the center of pressure (CoP). The CoM‐CoP gap in the sagittal plane was determinant for setting the disequilibrium torque and thus walking velocity. Thus, by controlling the gap, CNS‐modified walking velocity (GI, R2 = 0.86; BR, R2 = 0.92). This study is the first to highlight that by merely counteracting gravity, triceps activity sets the kinematics and kinetics of gait. It also provides evidence that the surge in triceps activity during fast walking is due to the increased requirement of braking the fall of CoM in late stance in order to perform a smoother step‐to‐step transition.

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