Abstract
This study investigates how external vertical forces on the pelvis change the stability of stairmill climbing and other gait parameters such as kinematics and muscle activity. We use a Tethered Pelvic Assist Device (TPAD) to apply forces on the pelvis during continuous ascent on a stairmill. Ten young healthy subjects participated in three one-minute stair ascent with no force, a 10% body weight (BW) downward force, and a 10% BW upward force applied on the pelvis. The stability is determined by evaluating the base of support (BoS) and margin of stability (MoS). Kinematics and muscle activities were used to characterize the biomechanical changes. The results show that the upward forces applied on the pelvis decreased the (i) MoS by 1.84cm in the lateral direction, 2.07cm in the anterior direction, (ii) double stance phase by 1.85%, and (iii) the knee flexion by 5°. Furthermore, the peak activation levels of the muscles rectus femoris (RF), vastus lateralis (VL), and left gastrocnemius decreased. In contrast, the downward forces applied on the pelvis increased (i) the MOS by 1.5cm in the anterior direction and (ii) mean activation levels of RF and VL muscles. This study provides insights into the effects of applied vertical forces on the pelvis during stair ascent. These findings contribute to the understanding of the gait parameter changes and their relation with stability. Results could be used as a basis for designing training protocols to improve balance during stair ascent.
Highlights
This study investigates how external vertical forces on the pelvis change the stability of stairmill climbing and other gait parameters such as kinematics and muscle activity
Reeves et al found that older subjects generated smaller center of mass (CoM)-center of pressure (CoP) separation because they were more cautious during stair ascent
When compared with overground walking, stair ascent requires a larger range of motion of the leg joints and higher knee moments to raise the center of mass (CoM) upward and forward while maintaining balance [1,2,3,4]
Summary
This study investigates how external vertical forces on the pelvis change the stability of stairmill climbing and other gait parameters such as kinematics and muscle activity. This study provides insights into the effects of applied vertical forces on the pelvis during stair ascent These findings contribute to the understanding of the gait parameter changes and their relation with stability. By assessing CoM-CoP separation in mediolateral and anteroposterior directions, they concluded that stair ascent required more time to stabilize the body, leading to longer double stance time than during descent or during level walking. This CoM-CoP separation parameter was used in other studies to compare the balance performance of young healthy adults and older healthy adults during three to four steps stair ascent [9,10,11]. The relative distance between CoM and center of pressure (CoP), named CoM-CoP separation, during stair ascent was first studied by Zachazewski et al on a three-step stationary
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