Effects of the type and direction of support surface perturbation on postural responses

Abstract

BackgroundPostural control is organized around a task goal. The two most frequently used types of tasks for postural control research are translational (translation along the anterior-posterior axis) and rotational (rotation in sagittal plane) surface perturbations. These types of perturbations rotate the ankle joint, causing different magnitudes and directions of body sway. The purpose of this study was to investigate the effects of the type (translation vs. rotation) and direction (forward/toe up vs. backward/toe down) of the perturbation on postural responses.MethodNineteen healthy subjects were tested with four perturbations, i.e., forward and backward translation and toe up and toe down rotation. The onset latency and magnitude of muscle activations, angular changes, and COM displacements were measured. In addition, the kinematic data were divided into two phases. The initial phase reflected the balance disturbance induced by the platform movement, and the reversal phase reflected the balance reaction.ResultsThe results showed that, in the initial phase, rotational perturbation induced earlier ankle movement and faster and larger vertical COM displacement, while translational and forward/toe up perturbations induced larger head and trunk angular change and faster and larger horizontal COM displacement. In the reversal phase, balance reaction was attained by multi-joint movements. Translational and forward/toe up perturbations that induced larger upper body instability evoked faster muscle activation as well as faster and larger hip or knee joint movements.ConclusionsThese findings provide insights into an appropriate support surface perturbation for the evaluation and training of balance.

Specific Stimuli Induce Specific Adaptations: Sensorimotor Training vs. Reactive Balance Training

“…In contrast, experiments executed in perturbed upright stance revealed that the proximal segment moves into focus to relocate the COM back to the vertical (Fig 1) [10,16,27]. It is supposed that—in contrast to the distal control during SMT—the control of the trunk is the fundamental strategy to keep equilibrium after perturbation [23,24,65] and stabilizing joint torques are distributed from the ankle towards the knee and hip joints [16,24,35,36]. …”

Inertial compensation for belt acceleration in an instrumented treadmill

“…Horizontal acceleration of the ground surface is commonly used in experiments to perturb posture and gait (Park et al, 2004;Chen et al, 2014). In order to determine joint moments during such tests, ground reaction forces must be measured, but this is problematic when the force plate is not rigidly attached to an inertial reference frame.…”

Time Window of Perturbation-Induced Response Triggered by Ankle Motion and Body Sway above the Ankle

“…The postural perturbation was induced by a combination of horizontal translation and rotation of the support surface in the enhanced and nulled ankle input tasks. This caused the interpretation of the findings to be difficult, as these two support surface movements induced different postural responses [4,5]. Accordingly, the time window of the EMG response component triggered by the somatic sensation derived from a particular body part is still a matter of investigation.…”