Amir Shapiro

Perturbation exercises during treadmill walking improve pelvic and trunk motion in older adults—A randomized control trial

BACKGROUNDnMost falls among older adults occur while walking. Pelvic and trunk motions are required to maintain stability during walking. We aimed to explore whether training that incorporates unexpected loss of balance during walking that evokes balance recovery reactions will improve pelvic, thorax, and trunk kinematics at different walking speeds.nnnMETHODSnFifty-three community-dwelling older adults (age 80.1u202f±u202f5.6u202fyears) were randomly allocated to an intervention group (nu202f=u202f27) or a control group (nu202f=u202f26). Both groups received 24 training sessions over 3 months. The intervention group received unexpected perturbation of balance exercises during treadmill walking, while the control group performed treadmill walking only. The primary outcome measures were the pelvic, thorax, and trunk motion. The secondary outcome measures were stride times, length, and width.nnnRESULTSnCompared to control, participation in the intervention program led to improvement in pelvic and trunk transverse rotations especially at participants preferred walking speed. No improvement where found in pelvic list while thorax transverse rotation improved in both groups.nnnCONCLUSIONSnPelvic and trunk transverse motion, parameters previously reported to deteriorate during aging, associated with gait stability and a risk factor for falls, can be improved by gait training that includes unexpected loss of balance.

A Novel Design of a Quadruped Robot for Research Purposes

This paper presents the design of a novel quadruped robot. The proposed design is characterized by a simple, modular design, and easy interfacing capabilities. The robot is built mostly from off-the-shelf components. The design includes four 3-DOF legs, the robot body and its electronics. The proposed robot is able to traverse rough terrain while carrying additional payloads. Such payloads can include both sensors and computational hardware. We present the robot design, the control system, and the forward and inverse kinematics of the robot, as well as experiments that are compared with simulation results.

The inter-observer reliability and agreement of lateral balance recovery responses in older and younger adults

The purpose of this study was to evaluate the inter-observer reliability and agreement of balance recovery responses, step and multiple-steps thresholds, and kinematic parameters of stepping responses. Older and younger adults were exposed to 36 progressively challenging right and left unannounced surface translations during quiet standing. Subjects were instructed to react naturally. Step threshold and multiple-step threshold were defined as the minimum disturbance magnitude that consistently elicited one and more than one recovery step, respectively. Fall threshold is defined as the minimum disturbance magnitude from which a fall resulted (i.e., fall into harness system or grasped one of the anchor straps of the harness, or grasped the research assistant to maintain balance). The inter-observer reliability of balance recovery responses for older adults were excellent, especially for step and multiple-step thresholds (ICC2,1u202f=u202f0.978 and ICC2,1u202f=u202f0.971, respectively; pu202f<u202f0.001). Also kinematic parameters of stepping responses such as step recovery duration and step length were excellent (ICC2,1u202f>u202f0.975 and ICC2,1u202f=u202f0.978, respectively; pu202f<u202f0.001), substantial reliability was found for swing phase duration (ICC2,1u202f=u202f0.693, pu202f<u202f0.001). Younger adults showed similar ICCs. The Bland-Altman plots demonstrated excellent limits of agreement (LOAu202f>u202f90%) for most kinematic step parameters and stepping thresholds. These results suggest that balance recovery responses and kinematic parameters of stepping including step threshold and multiple-step threshold are extremely reliable parameters. The measure of balance recovery responses from unexpected loss of balance is feasible and can be used in clinical setting and research-related assessments of fall risk.

On Laterally Perturbed Human Stance: Experiment, Model, and Control

Understanding human balance is a key issue in many research areas. One goal is to suggest analytical models for the human balance. Specifically, we are interested in the stability of a subject when a lateral perturbation is being applied. Therefore, we conducted an experiment, laterally perturbing five subjects on a mobile platform. We observed that the recorded motion is divided into two parts. The legs act together as a first, the head-arms-trunk segment as a second rigid body with pelvis, and the ankle as hinge joints. Hence, we suggest using a planar double-inverted pendulum model for the analysis. We try to reproduce the human reaction utilizing torque control, applied at the ankle and pelvis. The fitting was realized by least square and nonlinear unconstrained optimization on training sets. Our model is not only able to fit to the human reaction, but also to predict it on test sets. We were able to extract and review key features of balance, like torque coupling and delays as outcomes of the aforementioned optimization process. Furthermore, the delays are well within the ranges typically for such compensatory motions, composed of reflex and higher level motor control.

Gait Coordination Deteriorates in Independent Old-Old Adults

Human gait is symmetric and bilaterally coordinated in young healthy persons. In this study, we aimed to explore the differences in bilateral coordination of gait as measured by the phase coordination index (PCI), gait asymmetry, and stride time variability of gait between four age groups. A total of 44 older adults were recruited: nine young-old (age 70-74 years), 26 old (age 75-84 years), nine old-old (>85 years and older), and 13 young adults (age 20-30 years). Subjects walked on a treadmill; walking speed was systematically increased from 0.5 to 0.9xa0m/s in steps of 0.1xa0m/s. There were marginal effects of age on PCI, significant main effects of walking speeds without interaction between walking speeds and age group. A difference in PCI could distinguish between youngs and late aging group, and only during their preferred treadmills walking speed. This study explicitly shows that bilateral coordination of walking is modified by gait speed, and deteriorates only at a very old age.