Biped robots with point feet demonstrate faster gaits and more natural dynamics while their gait planning is very difficult due to their underactuation. This research focuses on modelling, optimization and gait generation of two different real biped models including a telescopic springy biped model and compass gait biped with kneed swing leg. All of these models have point feet and their torso angle is constrained and they move in sagittal plane. The main difference of these models with their corresponding theoretical models is that to give realization to the gaits of these models the knee of their swing leg bends, clears the ground and straightens before touch-down. This increases degrees of freedom and divides single support phase to two sub-phases. Different phases of walking gait of each model including single support phase, touch-down event and double support phase are modeled using Lagrange equation and validity of equations are demonstrated. Then the dynamic equations of the phases are combined together to make dynamic model of a full walking gait. Afterwards, optimization parameters, objective functions and constraints are presented and successive stages of optimization are performed to find optimal gaits. The optimization diagrams are discussed and the needed motor torques for the optimal gait of each model are illustrated.

Purpose: Hemipelvectomy amputation is a surgical procedure in which the lower limb and part of the pelvis are removed. Although few studies are available on the performance of individuals with hip disarticulation while walking, there is no study on gait analysis of hemipelvectomy subjects. Therefore, this study aimed to evaluate the gait and stability of an individual with hemipelvectomy amputation. Methods: An individual with hemipelvectomy amputation on the right side participated in this study. He used a Canadian prosthesis with single axis ankle joint, 3R21 knee joint and 7E7 hip joint for more than 10 years. The kinetic and kinematic parameters were collected by a motion analysis system and a Kistler force plate. Results: There was a significant difference between knee, hip and ankle motion ranges and their related time periods on the sound and prosthesis sides. The stability of the subject was better in the anteropos terior direction, than the mediolateral direction. Results revealed a significant asymmetry between the sound and prosthesis sides. Conclusion: The obtained results suggested a significant asymmetry between the kinetic and kinematic performance of the sound and prosthesis sides, which may be due to lack of muscular power and alignment of prosthesis components.

Background: Falls are a common complication post-stroke and often induce due to poor balance. Given that falls often occur during walking, it is possible that gait patterns influence balance during walking. Walking post-stroke is frequently spatiotemporally asymmetric, which may reduce walking balance. The aim of this study was to determine the relationship between gait asymmetry and walking balance in persons with chronic stroke. Methods: Fifty-four persons with chronic stroke (34 men and 20 women) with the mean age of 57. 28 participated in this cross-sectional study. Participants walked at their self-selected speed to calculate gait asymmetry ratios for stance time, swing time, and step length. The data were collected using a conventional camera with a sampling frequency of 60 Hz. Reflective markers were attached to the heel and toe regions. Participants also performed walking balance tests including Functional Gait Assessment (FGA) and Mini Balance Evaluation System Test (Mini-BESTest). Pearson correlation test was used to determine the relationships between gait asymmetry and walking balance. Results: The mean± standard deviation values of stance, swing and step asymmetry ratios and FGA and Mini-BESTest were 1. 2± 0. 11, 1. 43± 0. 24, 1. 25± 0. 15, 24. 11± 2. 93 and 22. 87± 2. 29, respectively. Increased FGA and Mini-BESTest scores were related to decreased swing (r=-0. 64, P≤ 0. 001 and, r=-0. 71, P≤ 0. 0001, respectively) and step asymmetry (r=-0. 41, P≤ 0. 002 and, r=-0. 51, P≤ 0. 001, respectively). No significant relationship was identified between FGA, and Mini-BESTest and stance asymmetry (r=-0. 25, P≤ 0. 06 and r=-0. 23, P≤ 0. 08 respectively). Conclusion: According to the current results spatiotemporal gait asymmetry may be related to decreased balance during walking in individuals with chronic stroke suggesting that rehabilitation interventions should focus specifically on ameliorating spatiotemporal gait asymmetry.

Background and Aims: Since walking and other tasks are simultaneously among the most common human activities, and considering the fact that that a large part of the elderly falls are during two tasks, the purpose of the present study was to examine the effect of walking speed and cognitive load on gait stability in the elderly. Materials and Methods: A total of 10 healthy volunteer elderly (5 males and 5 females) without a history of falls took part in the study. They were asked to perform 3 walking trails on a treadmill, including walking at 3 paces (preferred, fast, and slow) with/without cognitive load. Cognitive task was performed by subtracting 3's from a random three digit number. The gait-stability ratio (GSR) was calculated for each of the above conditions. Two-way repeated measures ANOVA was used to examine the mean differences at the significance level of 0. 05. Results: The findings showed that the cognitive performance score decreases with increasing speed and at faster speeds, compared with speed with cognitive load, GSR was found to be higher (p<0. 01). Conclusion: The results showed that the elderly, through different walking strategies, especially the shorter phase, provide more dual support while walking, so that they will fall less with increasing steadiness.

The characteristics of vertical ground reaction force (VGRF) gait patterns in children with autism spectrum disorders (ASD) are poorly understood. The purpose of this study was to identify VGRF gait features that discriminate between children with ASD and the peer control group. The VGRF data were obtained from 30 children with ASD and 30 normal healthy children aged 4 to 12 years. A three-dimensional motion analysis system with eight cameras and two force plates were used to collect VGRF data while subjects performed self-selected speed of barefoot walking. Parameterization techniques were applied to VGRF waveforms to extract the VGRF gait features. Mean significant differences between the two groups were tested using independent samples t-test and Mann-Whitney U test. Significant group differences were found for four VGRF gait features. Results indicated that children with ASD exhibited a significant reduction of the second peak of VGRF, earlier relative time to the occurrence of the second peak of VGRF, lower push-off rate, and higher peak ratio of the two VGRF peaks during normal speed of walking. These prominent differences showed that children with ASD had difficulties in supporting their body weight during terminal stance phase and these conditions affect the gait instability. The findings of this study develop further understanding of VGRF gait patterns that significantly differentiate between children with ASD and the peer control groups.