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. Author manuscript; available in PMC: 2020 May 1.
Published in final edited form as: Gait Posture. 2019 Mar 5;70:222–228. doi: 10.1016/j.gaitpost.2019.03.002

Table 2: Dependent variables and their definitions.

The limb that initiated the first recovery step was labeled as the stepping limb and the contralateral limb was labeled as the base limb. Margin of stability (MOS) was adopted from Hof et al., 2005 [35].

Dependent variables Definition
Reaction time Time from perturbation onset to SS.
Step duration Time from SS to SE.
Step length Anteroposterior distance between the centers of stepping foot segment and base foot at SE.
Trunk flexion Sagittal plane angle of the line connecting the center of the pelvis to the midpoint of the line connecting the shoulder markers relative to the initial position of the trunk at perturbation onset. Positive values representing a forward trunk tilt.
Trunk flexion velocity Time derivative of the Trunk flexion.
Dx Anteroposterior distance between vertical projection of center of mass (COM) position and the edge of the base of support (stepping leg toe marker) with positive values indicating COM to be within the boundary of the base of support (dynamically stable).
Margin of stability (MOS) A dynamic stability measure calculated using both anteroposterior position and velocity of COM relative to the edge of the base of support with positive values representing dynamically stable and negative values indicating dynamically unstable conditions.

Abbreviations: SS: step_start, SE: step_end, COM: center of mass, MOS: Margin of stability.