scholarly journals Development of a Mechanistic Hypothesis Linking Compensatory Biomechanics and Stepping Asymmetry during Gait of Transfemoral Amputees

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Abeer Mohamed ◽  
Andrew Sexton ◽  
Kirsten Simonsen ◽  
Chris A. McGibbon
Keyword(s):  
Stance Phase ◽  
Heel Strike ◽  
Knee Prostheses ◽  
Phase Duration ◽  
Double Support ◽  
Working Hypothesis ◽  
Intact Knee ◽  
Intact Limb ◽  
Support Phase ◽  
Double Support Phase

Objective. Gait asymmetry is a common adaptation observed in lower-extremity amputees, but the underlying mechanisms that explain this gait behavior remain unclear for amputees that use above-knee prostheses. Our objective was to develop a working hypothesis to explain chronic stepping asymmetry in otherwise healthy amputees that use above-knee prostheses. Methods. Two amputees (both through-knee; one with microprocessor knee, one with hydraulic knee) and fourteen control subjects participated. 3D kinematics and kinetics were acquired at normal, fast, and slow walking speeds. Data were analyzed for the push-off and collision limbs during a double support phase. We examined gait parameters to identify the stepping asymmetry then examined the external work rate (centre of mass) and internal (joint) power profiles to formulate a working hypothesis to mechanistically explain the observed stepping asymmetry. Results. Stepping asymmetry at all three gait speeds in amputees was characterized by increased stance phase duration of the intact limb versus relatively normal stance phase duration for the prosthesis limb. The prosthesis limb contributed very little to positive and negative work during the double support phase of gait. To compensate, the intact leg at heel strike first provided aid to the deficient prosthetic ankle/foot during its push-off by doing positive work with the intact knee, which caused a delayed stance phase pattern. The resulting delay in toe-off of the intact limb then facilitated the energy transfer from the more robust intact push-off limb to the weaker colliding prosthesis side. This strategy was observed for both amputees. Conclusions. There is a sound scientific rationale for a mechanistic hypothesis that stepping asymmetry in amputee participants is a result of a motor adaptation that is both facilitating the lower-leg trajectory enforced by the prosthesis while compensating for the lack of work done by the prosthesis, the cost of which is increased energy expenditure of the intact knee and both hips.

scholarly journals Immediate effects of a novel walking assist device with auxiliary illuminator on patients after acute strokes

2019 ◽  
Vol 39 (02) ◽  
pp. 115-124
Author(s):  
Wan-Yun Huang ◽  
Sheng-Hui Tuan ◽  
Min-Hui Li ◽  
Xin-Yu Liu ◽  
Pei-Te Hsu
Keyword(s):  
Gait Speed ◽  
Stride Length ◽  
Stance Phase ◽  
Gait Cycle ◽  
Swing Phase ◽  
Heel Strike ◽  
Assist Device ◽  
Double Support ◽  
Strike Angle ◽  
Support Phase

Background: Many patients after acute stage of stroke are present with abnormal gait pattern due to weakness or hypertonicity of the affected limbs. Facilitation of normal gait is a primary goal of rehabilitation on these patients.Objective: We aimed to investigate whether walking assist device with auxiliary illuminator (quad-cane with laser) providing visual feedback during ambulation could improve parameters of gait cycle immediately among patients with subacute and chronic stroke.Methods: This was a cross-sectional study and 30 participants (male 23, female 7, group 1) with mean age [Formula: see text] years were recruited. Among them, 22 used ankle-foot orthosis [(AFO), group 2] and 8 did not use AFO (group 3) at usual walking. All the participants walked along a strait corridor with even surface for 20[Formula: see text]m without and with using a quad-cane with laser, respectively. A gait analyzer (Reha-Watch1 system) was used to measure the changes of the parameters of gait cycle, including stride length, cadence, gait speed, stance phase, swing phase, duration of single support and double support, the angle between toes and the ground at the time of toe-off (the toe-off angle) and the angle between calcaneus and the ground at the time of heel-strike (the heel-strike angle), before and with the use of a quad-cane with laser.Results: The increase in the heel-strike angle reached a significant difference in groups 1 2, and 3 ([Formula: see text], and [Formula: see text], respectively). However, the stride length, the gait speed, the cadence, percentage of the stance phase, swing phase, single-support phase, and double-support phase in a gait cycle, and the toe-off angle showed no significant change with the use of quad-cane with laser.Conclusion: Patients after acute stroke had an immediate and significant increase in the heel-stroke angle by using a quad-cane with laser during ambulation, which might help the patients to reduce knee hyperextension moment and lessen the pressure of heel at loading phase.

scholarly journals Overground Walking Decreases Alpha Activity and Entrains Eye Movements in Humans

2020 ◽  
Vol 14 ◽  
Author(s):  
Liyu Cao ◽  
Xinyu Chen ◽  
Barbara F. Haendel
Keyword(s):  
Eye Movements ◽  
Neuronal Activity ◽  
Walking Speed ◽  
Alpha Activity ◽  
Alpha Power ◽  
Electrode Impedance ◽  
Blink Rate ◽  
Double Support ◽  
Support Phase ◽  
Double Support Phase

Experiments in animal models have shown that running increases neuronal activity in early visual areas in light as well as in darkness. This suggests that visual processing is influenced by locomotion independent of visual input. Combining mobile electroencephalography, motion- and eye-tracking, we investigated the influence of overground free walking on cortical alpha activity (~10 Hz) and eye movements in healthy humans. Alpha activity has been considered a valuable marker of inhibition of sensory processing and shown to negatively correlate with neuronal firing rates. We found that walking led to a decrease in alpha activity over occipital cortex compared to standing. This decrease was present during walking in darkness as well as during light. Importantly, eye movements could not explain the change in alpha activity. Nevertheless, we found that walking and eye related movements were linked. While the blink rate increased with increasing walking speed independent of light or darkness, saccade rate was only significantly linked to walking speed in the light. Pupil size, on the other hand, was larger during darkness than during light, but only showed a modulation by walking in darkness. Analyzing the effect of walking with respect to the stride cycle, we further found that blinks and saccades preferentially occurred during the double support phase of walking. Alpha power, as shown previously, was lower during the swing phase than during the double support phase. We however could exclude the possibility that the alpha modulation was introduced by a walking movement induced change in electrode impedance. Overall, our work indicates that the human visual system is influenced by the current locomotion state of the body. This influence affects eye movement pattern as well as neuronal activity in sensory areas and might form part of an implicit strategy to optimally extract sensory information during locomotion.

scholarly journals Dysfunctional muscle activities and co-contraction in the lower-limb of lumbar disc herniation patients during walking

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Wei Wang ◽  
Hui Wei ◽  
Runxiu Shi ◽  
Leitong Lin ◽  
Lechi Zhang ◽  
...  
Keyword(s):  
Lumbar Disc Herniation ◽  
Disc Herniation ◽  
Lower Limb ◽  
Gait Cycle ◽  
Lumbar Disc ◽  
Lower Limbs ◽  
Heel Strike ◽  
Control Group ◽  
Double Support ◽  
Support Phase

AbstractThis study aimed to investigate lower-limb muscle activities in gait phases and co-contraction of one gait cycle in patients with lumbar disc herniation (LDH). This study enrolled 17 LDH patients and 17 sex- and age-matched healthy individuals. Bilateral muscle activities of the rectus femoris (RF), biceps femoris long head (BL), tibialis anterior (TA), and lateral gastrocnemius (LG) during walking were recorded. The gait cycle was divided into four phases by the heel strike and top off according to the kinematics tracks. Root mean square (RMS), mean frequency (MF), and co-contraction of surface electromyography signals were calculated. The LDH patients showed enhanced BL RMS during the single support phase (SS), second double support phase, and swing phase (SW) as well as decreased MF of RF during SS and of TA and LG during SW (p < 0.05). The co-contraction of the TA-LG was increased in LDH patients than in the control group (p < 0.05). Positive correlations were observed between TA-LG co-contraction (affected side, r = 0.557, p = 0.020; contralateral side, r = 0.627, p = 0.007) and the Oswestry disability index scores in LDH patients. LDH patients have increased BL firing rate and insufficient motor unit recruitment in specific phases in the lower limbs during walking. Dysfunction in LDH patients was associated with immoderate intermuscular co-contraction of the TA-LG during walking.

Development of multi-phase dynamic equations for a seven-link biped robot with improved foot rotation in the double support phase

2014 ◽  
Vol 229 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Farsam Farzadpour ◽  
Mohammad Danesh ◽  
Seyed M TorkLarki
Keyword(s):  
Power Consumption ◽  
Trajectory Generation ◽  
Biped Robot ◽  
Dynamic Equations ◽  
Total Power ◽  
Phase Dynamic ◽  
Double Support ◽  
Multi Phase ◽  
Support Phase ◽  
Double Support Phase

Gait generation plays a significant role in the quality of locomotion of legged robots. This paper presents the development of multi-phase dynamic equations and optimal trajectory generation for a seven-link planar-biped robot walking on the ground level with consideration of feet rotation in the double support phase. The main contribution of this paper is to increase the stability margin at the phase transition time for simultaneous feet rotation in double support phase by introducing a new style of feet rotation. First, the derivation of the dynamics equations, which is a challenging problem due to the existence of the holonomic constraints, is performed using the Lagrangian formulation. Then, an analytical solution to inverse kinematics is proposed to determine the angles of each joint. A multi-objective genetic algorithm-based optimization technique is proposed to obtain the key parameters in trajectory generation so that the zero moment point tracks a predefined stable trajectory and additionally minimizes the power consumption, which is subjected to actuators’ powers limitations. The effect of the hip height on the total power consumption is also investigated. The numerical simulations demonstrate the effectiveness of the proposed method.

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