Shifts of the center of pressure (CoP) through modulation of foot placement and ankle moments (CoP-mechanism) cause accelerations of the center of mass (CoM) that can be used to stabilize gait. An additional mechanism that can be used to stabilize gait, is the counter-rotation mechanism, i.e., changing the angular momentum of segments around the CoM to change the direction of the ground reaction force. The relative contribution of these mechanisms to the control of the CoM is unknown. Therefore, we aimed to determine the relative contribution of these mechanisms to control the CoM in the anteroposterior (AP) direction during a normal step and the first recovery step after perturbation in healthy adults. Nineteen healthy subjects walked on a split-belt treadmill and received unexpected belt acceleration perturbations of various magnitudes applied immediately after right heel-strike. Full-body kinematic and force plate data were obtained to calculate the contributions of the CoP-mechanism and the counter-rotation mechanism to control the CoM. We found that the CoP-mechanism contributed to corrections of the CoM acceleration after the AP perturbations, while the counter-rotation mechanism actually counteracted the CoM acceleration after perturbation, but only in the initial phases of the first step after the perturbation. The counter-rotation mechanism appeared to prevent interference with the gait pattern, rather than using it to control the CoM after the perturbation. Understanding the mechanisms used to stabilize gait may have implications for the design of therapeutic interventions that aim to decrease fall incidence.

通过调整脚的位置和脚踝力矩（CoP机理）引起的压力中心（CoP）的偏移会导致质心（CoM）的加速度，该加速度可用于稳定步态。可以用来稳定步态的另一种机制是反向旋转机制，即，更改围绕CoM的线段的角动量以更改地面反作用力的方向。这些机制对CoM控制的相对贡献尚不清楚。因此，我们旨在确定健康成年人在正常步骤和扰动后的第一个恢复步骤中，控制前后方向（AP）方向上CoM的这些机制的相对贡献。十九名健康受试者在右脚跟撞击后立即在皮带式跑步机上行走，并受到各种程度的意外皮带加速扰动。获得了全身运动学和力板数据，以计算CoP机制的作用以及控制CoM的反向旋转机制。我们发现CoP机制有助于AP扰动后CoM加速度的校正，而反向旋转机制实际上抵消了扰动后的CoM加速度，但仅在扰动之后的第一步的初始阶段起作用。反向旋转机制似乎是在防止干扰步态模式，而不是在扰动后使用它来控制CoM。