3D intersegmental knee loading in below-knee amputees across steady-state walking speeds

Pedestrian accident analysis and reconstruction remain the most difficult areas for the accident analyst. Although data relating to average pedestrian walking speeds, perception-reaction, and pedestrian accident reconstruction can be found in the literature, proper pedestrian study data pertaining to real-life situations are lacking. Pedestrians were observed at signal-controlled crosswalk intersections, and their perception-reaction to the crosswalk signal, acceleration rate to reach constant walking velocity, and average walking speed once steady state velocity is achieved were determined. Experimental test data collected regarding pedestrian gait analysis, initiation, and steady state walking speeds are presented. “Real world” pedestrian observations were gathered at a variety of intersections, ranging from busy downtown intersections to suburban intersections throughout the greater Los Angeles area. Kinematic data on pedestrian movements were obtained using high-speed digital video. A high-speed video motion analysis system was used to reduce the data and to obtain the mean acceleration and time to steady state walking velocity. Perception-reaction data collected on 288 subjects show a significant percentage of the pedestrians initiating movement within 1 s of Walk light illumination. Some differences were observed when the state of anticipation was being considered, and these results are presented. The mean acceleration (0.14 ± 0.09 g) and steady state velocity (1.36 ± 0.24 m/s) values did not demonstrate a significant difference between males and females. The width of the street or initial state of anticipation did not have an effect on either mean acceleration values or steady state velocities.

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Simulating bipedal walking using a translating center of pressure

10.1101/723445 ◽

2019 ◽

Author(s):

Karna Potwar ◽

Dongheui Lee

Keyword(s):

Steady State ◽

Walking Speed ◽

Center Of Pressure ◽

Reaction Force ◽

Bipedal Walking ◽

Upper Body ◽

Foot Placement ◽

Fast Walking ◽

Walking Speeds ◽

Steady State Solutions

AbstractDuring walking, foot orientation and foot placement allow humans to stabilize their gait and to move forward. Consequently the upper body adapts to the ground reaction force (GRF) transmitted through the feet. The foot-ground contact is often modeled as a fixed pivot in bipedal models for analysis of locomotion. The fixed pivot models, however, cannot capture the effect of shift in the pivot point from heel to toe. In this study, we propose a novel bipedal model, called SLIPCOP, which employs a translating center of pressure (COP) in a spring loaded inverted pendulum (SLIP) model. The translating COP has two modes: one with a constant speed of translation and the other as the weighted function of the GRF in the fore aft direction. We use the relation between walking speed and touchdown (TD) angle as well as walking speed and COP speed, from existing literature, to restrict steady state solutions within the human walking domain. We find that with these relations, SLIPCOP provides steady state solutions for very slow to very fast walking speeds unlike SLIP. SLIPCOP for normal to very fast walking speed shows good accuracy in estimating COM amplitude and swing stance ratio. SLIPCOP is able to estimate the distance traveled by the COP during stance with high precision.

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Compensatory mechanisms in below-knee amputee gait in response to increasing steady-state walking speeds

Gait & Posture ◽

10.1016/j.gaitpost.2008.04.005 ◽

2008 ◽

Vol 28 (4) ◽

pp. 602-609 ◽

Cited By ~ 102

Author(s):

Anne K. Silverman ◽

Nicholas P. Fey ◽

Albert Portillo ◽

Judith G. Walden ◽

Gordon Bosker ◽

...

Keyword(s):

Steady State ◽

Compensatory Mechanisms ◽

Walking Speeds ◽

Amputee Gait

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The Effect of Aquatic and Land-Based Training on the Metabolic Cost of Walking and Motor Performance in Children with Cerebral Palsy: A Pilot Study

ISRN Rehabilitation ◽

10.5402/2012/657979 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

Miriam Getz ◽

Yeshayahu Hutzler ◽

Adri Vermeer ◽

Yoni Yarom ◽

Viswanath Unnithan

Keyword(s):

Cerebral Palsy ◽

Steady State ◽

Motor Function ◽

Walking Speed ◽

Metabolic Cost ◽

Gross Motor ◽

Gross Motor Function ◽

Children With Cerebral Palsy ◽

Parametric Statistics ◽

Walking Speeds

Aim. To evaluate the effects of aquatic (AQ) compared to a land-based (LB) intervention programs on metabolic cost of walking (MCW), gross motor function and locomotor performance in children with cerebral palsy (CP). Methods. Eleven children with spastic diplegic CP completed this study, six in the AQ (5.2 ± 1.45 yrs) and five in the LB group (4.1 ± 1.33 yrs). MCW derived from Oxygen uptake (VO2) measured with a Cosmed K4 device and walking speed at steady state. Additional measures included the 10-m test, Gross Motor Function Measure (GMFM), and Pediatric Evaluation Developmental Inventory (PEDI). Non-parametric statistics were used to analyze change in each group. Results. The AQ group significantly decreased MCW (Z=−2.2; P<.05) and increased steady state walking speed (Z=−2.2; P<.05). Both groups significantly increased 10-m walking speed (Z=−2.2; P<.03, and Z=−2.02; P<.05, resp.). The LB group exhibited moderate to large effect sizes in 10-m self-selected and fast walking speeds (Cohen's d=1.07 and 0.73, resp.). Conclusion. Our findings suggest that Both AQ and LB programs were effective in improving 10-m speed, while the AQ training also improved the MCW of walking at steady state in children with spastic diplegic CP.

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The Effect of High- and Low-Damping Prosthetic Foot Structures on Knee Loading in the Uninvolved Limb Across Different Walking Speeds

Journal of Applied Biomechanics ◽

10.1123/jab.2015-0143 ◽

2016 ◽

Vol 32 (3) ◽

pp. 233-240 ◽

Cited By ~ 6

Author(s):

Li Jin ◽

Peter G. Adamczyk ◽

Michelle Roland ◽

Michael E. Hahn

Keyword(s):

Knee Osteoarthritis ◽

Frontal Plane ◽

Limb Amputation ◽

Loading Rates ◽

Prosthetic Foot ◽

Fast Speed ◽

Peak Knee ◽

Knee Loading ◽

Young Subjects ◽

Walking Speeds

Lower limb amputation has been associated with secondary impairments such as knee osteoarthritis in the uninvolved limb. Greater knee loading in the frontal plane has been related to severity and rate of progression in knee osteoarthritis. Reduced push-off work from the involved limb can increase uninvolved limb knee loading. However, little is known about specific effects that prosthetic foot damping may have on uninvolved limb loading. We hypothesized that uninvolved limb peak knee internal abduction moment (IAM) and loading rates would be greater when using a high-damping foot compared with a low-damping foot, across walking speeds. Eight healthy, young subjects walked in a prosthesis simulator boot using the experimental feet. Greater uninvolved limb first peak IAM (+16% in fast speed, P = .002; +11% in slow speed, P = .001) and loading rates (+11% in fast speed, P = .003) were observed when using the high-damping foot compared with low-damping foot. Within each foot, uninvolved limb first peak IAM and loading rates had a trend to increase with increased walking speed. These findings suggest that damping properties of prosthetic feet are related to uninvolved limb peak knee IAM and loading rates.

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Walking economy is predictably determined by speed, grade, and gravitational load

Journal of Applied Physiology ◽

10.1152/japplphysiol.00504.2017 ◽

2017 ◽

Vol 123 (5) ◽

pp. 1288-1302 ◽

Cited By ~ 11

Author(s):

Lindsay W. Ludlow ◽

Peter G. Weyand

Keyword(s):

Steady State ◽

Metabolic Energy ◽

Human Walking ◽

Validation Data ◽

Data Set ◽

Mechanics Model ◽

Support Force ◽

Walking Economy ◽

Walking Speeds ◽

Speed Grade

The metabolic energy that human walking requires can vary by more than 10-fold, depending on the speed, surface gradient, and load carried. Although the mechanical factors determining economy are generally considered to be numerous and complex, we tested a minimum mechanics hypothesis that only three variables are needed for broad, accurate prediction: speed, surface grade, and total gravitational load. We first measured steady-state rates of oxygen uptake in 20 healthy adult subjects during unloaded treadmill trials from 0.4 to 1.6 m/s on six gradients: −6, −3, 0, 3, 6, and 9°. Next, we tested a second set of 20 subjects under three torso-loading conditions (no-load, +18, and +31% body weight) at speeds from 0.6 to 1.4 m/s on the same six gradients. Metabolic rates spanned a 14-fold range from supine rest to the greatest single-trial walking mean (3.1 ± 0.1 to 43.3 ± 0.5 ml O2·kg-body−1·min−1, respectively). As theorized, the walking portion (V̇o2-walk = V̇o2-gross – V̇o2-supine-rest) of the body’s gross metabolic rate increased in direct proportion to load and largely in accordance with support force requirements across both speed and grade. Consequently, a single minimum-mechanics equation was derived from the data of 10 unloaded-condition subjects to predict the pooled mass-specific economy (V̇o2-gross, ml O2·kg-body + load−1·min−1) of all the remaining loaded and unloaded trials combined ( n = 1,412 trials from 90 speed/grade/load conditions). The accuracy of prediction achieved ( r2 = 0.99, SEE = 1.06 ml O2·kg−1·min−1) leads us to conclude that human walking economy is predictably determined by the minimum mechanical requirements present across a broad range of conditions. NEW & NOTEWORTHY Introduced is a “minimum mechanics” model that predicts human walking economy across a broad range of conditions from only three variables: speed, surface grade, and body-plus-load mass. The derivation/validation data set includes steady-state loaded and unloaded walking trials ( n = 3,414) that span a fourfold range of walking speeds on each of six different surface gradients (−6 to +9°). The accuracy of our minimum mechanics model ( r2 = 0.99; SEE = 1.06 ml O2·kg−1·min−1) appreciably exceeds that of currently used standards.

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Studies on Water in the Hydration Chamber of a Modified Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069715 ◽

1970 ◽

Vol 28 ◽

pp. 544-545

Author(s):

R. C. Moretz ◽

G. G. Hausner ◽

D. F. Parsons

Keyword(s):

Thin Film ◽

Thin Films ◽

Electron Microscope ◽

Steady State ◽

Room Temperature ◽

Small Mass ◽

Equilibrium Pressure ◽

Biological Objects ◽

Mechanical Pump ◽

Differential Pumping

Use of the electron microscope to examine wet objects is possible due to the small mass thickness of the equilibrium pressure of water vapor at room temperature. Previous attempts to examine hydrated biological objects and water itself used a chamber consisting of two small apertures sealed by two thin films. Extensive work in our laboratory showed that such films have an 80% failure rate when wet. Using the principle of differential pumping of the microscope column, we can use open apertures in place of thin film windows.Fig. 1 shows the modified Siemens la specimen chamber with the connections to the water supply and the auxiliary pumping station. A mechanical pump is connected to the vapor supply via a 100μ aperture to maintain steady-state conditions.

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Continuous hydrogenolysis of acetal-stabilized lignin in flow

Green Chemistry ◽

10.1039/d0gc02928a ◽

2021 ◽

Author(s):

Wu Lan ◽

Yuan Peng Du ◽

Songlan Sun ◽

Jean Behaghel de Bueren ◽

Florent Héroguel ◽

...

Keyword(s):

Steady State ◽

Challenges And Opportunities

We performed a steady state high-yielding depolymerization of soluble acetal-stabilized lignin in flow, which offered a window into challenges and opportunities that will be faced when continuously processing this feedstock.

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