Mediolateral Upper-body Gyroscopic Moment Perturbations During Walking: Exploring Muscle Activation Patterns and Control Strategies

Abstract

Adaptive motor control and seamless coordination of muscle actions in response to external perturbations are crucial to maintaining balance during bipedal locomotion. There is an ongoing debate about the specific roles of individual muscles and underlying neural control circuitry that humans employ to maintain balance in different perturbation scenarios. To advance our understanding of human motor control in perturbation recovery, we conducted a study using a portable Angular Momentum Perturbator (AMP). Unlike other push/pull perturbation systems, the AMP can generate perturbation torques on the upper body while minimizing the perturbing forces at the center of mass. In this study, ten participants experienced trunk perturbations during either the mid-stance or touchdown phase in two frontal plane directions (ipsilateral and contralateral). We recorded and analyzed the electromyography (EMG) activity of eight lower-limb muscles from both legs to examine muscular responses in different phases and directions. Based on our findings, individuals primarily employ short-latency hip strategies to effectively counteract perturbation torques, with the occasional use of ankle strategies. Furthermore, it was found that proximal muscles such as Rectus Femoris, Hamstrings, and Tensor Fasciae Latae exhibited higher activation levels than other muscles. Additionally, we observed that the fastest reactions generally stem from muscles in close proximity to the perturbation site. However, the temporal sequence of muscles’ activation depends on the timing and direction of the perturbation. This suggests that, in response to unexpected torque perturbations, the body recruits the repertoire of muscles at its disposal, enabling effective coping with perturbations when necessary instead of relying on learned central motor programs. These findings enhance reflex response modeling, aiding the development of simulation tools for accurately predicting exogenous disturbances. Additionally, they hold the potential to shape the development of assistive devices, with implications for clinical interventions, particularly for the elderly.

Design of Low-Cost Modular Bioinspired Electric-Pneumatic Actuator (EPA) Driven Legged Robots

“…On the mechanical side, future work will involve the design of new iterations of the EPA robots to better reflect the same weight and inertia ratios of humans while still preserving the cost and modularity of the robot. On the biomechanical and control side, we aim to unlock the complete potential of the EPA approach by expanding its application to different forms of locomotion under both normal and perturbed conditions [70]. Building upon our previous work, we seek to gain a deeper understanding of the adaptations necessary in both EPA design and control mechanisms to match different locomotor subfunctions [1] seamlessly.…”

Design of Low-Cost Modular Bio-Inspired Electric–Pneumatic Actuator (EPA)-Driven Legged Robots

“…Another feasible arrangement involves a PAM crossing two joints, functioning as an energy exchanger. Bi-articular configurations have proven advantageous in terms of contributing to posture and body balance [ 70 ], increasing energy efficiency [ 71 ], and simplifying control tasks [ 16 ]. Our preliminary experimental results with EPA Jumper demonstrate the effects of the passive dynamic behavior provided by PAMs (in ankle and hip joints) to generate repetitive hops without demanding any extra effort for active control design.…”

“…On the mechanical side, future work will involve the design of new iterations of the EPA robots to better reflect the same weight and inertia ratios of humans while still preserving the cost and modularity of the robot. On the biomechanical and control side, we aim to unlock the complete potential of the EPA approach by expanding its application to different forms of locomotion under both normal and perturbed conditions [ 70 ]. Building upon our previous work, we seek to gain a deeper understanding of the adaptations necessary in both EPA design and control mechanisms to match different locomotor subfunctions [ 1 ] seamlessly.…”