NONLINEAR MODELING WITH CAVITATION PHENOMENON OF A NOVEL SHOCK ABSORBER FOR ABOVE-KNEE PROSTHESIS

2010 ◽  
Vol 07 (03) ◽  
pp. 243-257 ◽  
Author(s):  
Y. C. MAO
Keyword(s):  
Shock Wave ◽  
Ground Reaction Force ◽  
Shock Absorber ◽  
Knee Prosthesis ◽  
Reaction Force ◽  
Damping Coefficient ◽  
Heel Strike ◽  
Cavitation Phenomenon ◽  
Wide Range ◽  
The Impact

The shock wave of ground reaction forces during walking and running is suggested as a primary etiological agent in some conditions, such as degenerative joint disease, prosthetic joint loosening, plantar fasciitis or muscle tears. This study proposes a novel shock absorber design with an adjustable automatic smooth tuning range of the damping coefficient and rapid rebounds after impact loads, equipped in the above-knee prosthesis tibia section without any electronic devices. This absorber is also capable of automatic locking-out and releasing for stance and heel-strike phases without manual switching. It absorbs the impact load of the ground reaction force at each heel strike and adapts itself to the input force speed, feasible for patients to tolerate a wide range of athletic and inert situations. This study constructs a high order nonlinear dynamic model for its pressure-sensitive plunger and check valve systems and considers the cavitation phenomenon during speedy fluid flows. Simulation results show that both the damper resistant force and the damping coefficient reduce as the ground reaction force velocity increases, providing a desirable tendency of diminishing shock wave influences on the biological musculoskeletal system.

Dynamic Modeling and Fluid-Structure Interactive Analysis of an Innovative Self-Tuning Shock Absorber for the Prosthesis Knee Joint

2010 ◽  
Author(s):  
Yen-Chieh Mao ◽  
Wei-Chih Chang
Keyword(s):  
Knee Joint ◽  
Shock Absorber ◽  
Knee Prosthesis ◽  
Element Model ◽  
Heel Strike ◽  
Design Parameters ◽  
Fluid Structure ◽  
Shock Absorbers ◽  
Damper Design ◽  
The Impact

The above-knee prosthesis, as a supplement of the lost biological leg, is supposed to provide equivalent or enhanced shock absorption capability and reduce the shock waves on the amputee body when walking and running. Prosthesis knee joint with a shock absorber is a feasible solution that efficiently absorbs the impact loads during each heel-strike. Conventional shock absorbers consist of springs and dampers with constant coefficients produce excessive rigid reactions when encountering impact forces, while unreasonable weak responses for gentle loads. This study proposes an innovative viscous damper design for the prosthesis knee joint which automatically and smoothly tunes the damping coefficient without any electronic components according to the input force velocities. High order differential system of the shock absorber is constructed and simulates the system dynamics during cyclic loads. The fluid-structure interactive finite element model for key components in the absorber is established in this study. Design parameters of the damper system under certain absorbing performance requirements are determined in this paper.

scholarly journals Optimal damping coefficient for a class of continuous contact models

2020 ◽  
Vol 50 (2) ◽  
pp. 169-188
Author(s):  
Mohammad Poursina ◽  
Parviz E. Nikravesh
Keyword(s):  
Contact Force ◽  
Analytical Formula ◽  
Coefficient Of Restitution ◽  
Damping Coefficient ◽  
Optimization Strategy ◽  
Continuous Contact ◽  
Optimal Damping ◽  
Wide Range ◽  
Contact Models ◽  
The Impact

Abstract In this study, we develop an analytical formula to approximate the damping coefficient as a function of the coefficient of restitution for a class of continuous contact models. The contact force is generated by a logical point-to-point force element consisting of a linear damper connected in parallel to a spring with Hertz force–penetration characteristic, while the exponent of deformation of the Hertz spring can vary between one and two. In this nonlinear model, it is assumed that the bodies start to separate when the contact force becomes zero. After separation, either the restitution continues or a permanent penetration is achieved. Therefore, this model is capable of addressing a wide range of impact problems. Herein, we apply an optimization strategy on the solution of the equations governing the dynamics of the penetration, ensuring that the desired restitution is reproduced at the time of separation. Furthermore, based on the results of the optimization process along with analytical investigations, the resulting optimal damping coefficient is analytically expressed at the time of impact in terms of system properties such as the effective mass, penetration velocity just before the impact, coefficient of restitution, and the characteristics of the Hertz spring model.

A 6-Week Transition to Maximal Running Shoes Does Not Change Running Biomechanics

2019 ◽  
Vol 47 (4) ◽  
pp. 968-973 ◽  
Author(s):  
J.J. Hannigan ◽  
Christine D. Pollard
Keyword(s):  
Ground Reaction Force ◽  
Loading Rate ◽  
Impact Force ◽  
Reaction Force ◽  
Vertical Ground Reaction Force ◽  
Risk Of Injury ◽  
Impact Peak ◽  
Running Shoes ◽  
Vertical Ground ◽  
The Impact

Background: A recent study suggested that maximal running shoes may increase the impact force and loading rate of the vertical ground-reaction force during running. It is currently unknown whether runners will adapt to decrease the impact force and loading rate over time. Purpose: To compare the vertical ground-reaction force and ankle kinematics between maximal and traditional shoes before and after a 6-week acclimation period to the maximal shoe. Study Design: Controlled laboratory study. Methods: Participants ran in a traditional running shoe and a maximal running shoe during 2 testing sessions 6 weeks apart. During each session, 3-dimensional kinematics and kinetics were collected during overground running. Variables of interest included the loading rate, impact peak, and active peak of the vertical ground-reaction force, as well as eversion and dorsiflexion kinematics. Two-way repeated measures analyses of variance compared data within participants. Results: No significant differences were observed in any biomechanical variable between time points. The loading rate and impact peak were higher in the maximal shoe. Runners were still everted at toe-off and landed with less dorsiflexion, on average, in the maximal shoe. Conclusion: Greater loading rates and impact forces were previously found in maximal running shoes, which may indicate an increased risk of injury. The eversion mechanics observed in the maximal shoes may also increase the risk of injury. A 6-week transition to maximal shoes did not significantly change any of these measures. Clinical Relevance: Maximal running shoes are becoming very popular and may be considered a treatment option for some injuries. The biomechanical results of this study do not support the use of maximal running shoes. However, the effect of these shoes on pain and injury rates is unknown.

scholarly journals The Kinematics and Kinetics Analysis of the Lower Extremity in the Landing Phase of a Stop-jump Task

2015 ◽  
Vol 9 (1) ◽  
pp. 103-107 ◽  
Author(s):  
L Yin ◽  
D Sun ◽  
Q.C Mei ◽  
Y.D Gu ◽  
J.S Baker ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Ground Reaction Force ◽  
Knee Flexion ◽  
Reaction Force ◽  
Flexion Angle ◽  
Contact Phase ◽  
Peak Knee ◽  
Significant Difference ◽  
The Impact ◽  
Kinematics And Kinetics

Large number of studies showed that landing with great impact forces may be a risk factor for knee injuries. The purpose of this study was to illustrate the different landing loads to lower extremity of both genders and examine the relationships among selected lower extremity kinematics and kinetics during the landing of a stop-jump task. A total of 35 male and 35 female healthy subjects were recruited in this study. Each subject executed five experiment actions. Lower extremity kinematics and kinetics were synchronously acquired. The comparison of lower extremity kinematics for different genders showed significant difference. The knee and hip maximum flexion angle, peak ground reaction force and peak knee extension moment have significantly decreased during the landing of the stop-jump task among the female subjects. The hip flexion angle at the initial foot contact phase showed significant correlation with peak ground reaction force during landing of the stop-jump task (r=-0.927, p<0.001). The knee flexion angle at the initial foot contact phase had significant correlation with peak ground reaction force and vertical ground reaction forces during landing of the stop-jump task (r=-0.908, p<0.001; r=0.812, P=0.002). A large hip and knee flexion angles at the initial foot contact with the ground did not necessarily reduce the impact force during landing, but active hip and knee flexion motions did. The hip and knee flexion motion of landing was an important technical factor that affects anterior cruciate ligament (ACL) loading during the landing of the stop-jump task.

Spectral Analysis of Impact Shock during Running

1992 ◽  
Vol 8 (4) ◽  
pp. 288-304 ◽  
Author(s):  
Martyn R. Shorten ◽  
Darcy S. Winslow
Keyword(s):  
Shock Wave ◽  
Wave Attenuation ◽  
Spectral Characteristics ◽  
Reaction Force ◽  
The Body ◽  
Treadmill Running ◽  
Running Speed ◽  
The Impact ◽  
Impact Shock Wave ◽  
Impact Shock

The purpose of this study was to determine the effects of increasing impact shock levels on the spectral characteristics of impact shock and impact shock wave attenuation in the body during treadmill running. Twelve male subjects ran at 2.0, 3.0, 4.0, and 5.0 m s−1on a treadmill. Axial accelerations of the shank and head were measured using low-mass accelerometers. The typical shank acceleration power spectrum contained two major components which corresponded to the active (5–8 Hz) and impact (12–20 Hz) phases of the time-domain ground reaction force. Both the amplitude and frequency of leg shock transients increased with increasing running speed. Greatest attenuation of the shock transmitted to the head occurred in the 15–50 Hz range. Attenuation increased with increasing running speed. Thus transmission of the impact shock wave to the head was limited, despite large increases in impact shock at the lower extremity.

scholarly journals Shock absorption during transtibial amputee gait: Does longitudinal prosthetic stiffness play a role?

2016 ◽  
Vol 41 (2) ◽  
pp. 178-185 ◽  
Author(s):  
Erin Boutwell ◽  
Rebecca Stine ◽  
Steven Gard
Keyword(s):  
Ground Reaction Force ◽  
Repeated Measures ◽  
Reaction Force ◽  
Shock Absorption ◽  
Appreciable Change ◽  
Normal Medium ◽  
Gait Biomechanics ◽  
Wide Range ◽  
Significant Difference ◽  
Transtibial Prosthesis

Background:Reduced-stiffness components are often prescribed in lower-limb prostheses, but their efficacy in augmenting shock absorption has been inconclusive.Objectives:To perform a systematic variation of longitudinal prosthetic stiffness over a wide range of values and to evaluate its effect on shock absorption during gait.Study design:Repeated-measures crossover experiment.Methods:Twelve subjects with a unilateral transtibial amputation walked at normal and fast self-selected speeds. Longitudinal prosthetic stiffness was modified by springs within a shock-absorbing pylon: normal (manufacturer recommended), 75% of normal (medium), 50% of normal (soft), and rigid (displacement blocked). The variables of interest were kinematic (stance-phase knee flexion and pelvic obliquity) and kinetic (prosthetic-side ground reaction force loading peak magnitude and timing).Results:No changes were observed in kinematic measures during gait. A significant difference in peak ground reaction force magnitudes between medium and normal ( p = 0.001) during freely selected walking was attributed to modified walking speed ( p = 0.008). Ground reaction force peaks were found to be statistically different during fast walking, but only between isolated stiffness conditions. Thus, altering longitudinal prosthesis stiffness produced no appreciable change in gait biomechanics.Conclusion:Prosthesis stiffness does not appear to substantially influence shock absorption in transtibial prosthesis users.Clinical relevanceVarying the level of longitudinal prosthesis stiffness did not meaningfully influence gait biomechanics at self-selected walking speeds. Thus, as currently prescribed within a transtibial prosthesis, adding longitudinal stiffness in isolation may not provide the anticipated shock absorption benefits. Further research into residual limb properties and compensatory mechanisms is needed.

scholarly journals Soft-tissue vibration and damping response to footwear changes across a wide range of anthropometrics in running

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256296
Author(s):  
Anja-Verena Behling ◽  
Marlene Giandolini ◽  
Vinzenz von Tscharner ◽  
Benno Maurus Nigg
Keyword(s):  
Soft Tissue ◽  
Muscle Activation ◽  
Lower Limbs ◽  
Damping Coefficient ◽  
Heel Strike ◽  
Damping Coefficients ◽  
Wide Range ◽  
Dominant Vibration Frequency ◽  
Tissue Compartments ◽  
Total Muscle

Different factors were shown to alter the vibration characteristics of soft-tissue compartments during running. Changing pre-heel strike muscle activation or changing footwear conditions represents two possibilities to influence the vibration response via frequency shift or altered damping. Associated with the study of muscle pre-tuning is the difficulty in quantifying clean experimental data for the acceleration of soft-tissue compartments and muscle activities in heterogeneous populations. The purpose of this study was to determine the vibration and pre-tuning response to footwear across a wide range of participants during running and establish and describe groups formed according to the damping coefficient. 32 subjects were used for further analysis. The subjects ran at a self-selected speed (5 min) on a treadmill in two different shoes (soft & hard), while soft-tissue accelerations and muscle activation at the gastrocnemius medialis were quantified. Damping coefficients, total muscle intensity and dominant vibration frequencies were determined. Anthropometrics and skinfold measurements of the lower limbs were obtained. According to the damping coefficient response to the footwear intervention, three groups were formed, with most runners (n = 20) showing less damping in the hard shoe. Total muscle intensity, anthropometrics, and dominant vibration frequency across footwear were not different for these three groups. Most runners (84.4%) used the strategy of adjusting the damping coefficients significantly when switching footwear. Despite damping being the preferred adjustment to changes in footwear, muscle pre-tuning might not be the only mechanism to influence damping as previously suggested. Future studies should focus on the subject-specific composition of soft-tissue compartments to elucidate their contribution to vibrations.

scholarly journals Accelerometer-based prediction of ground reaction force in head-out water exercise with different exercise intensity countermovement jump

2022 ◽  
Vol 14 (1) ◽  
Author(s):  
Kuei-Yu Chien ◽  
Wei-Gang Chang ◽  
Wan-Chin Chen ◽  
Rong-Jun Liou
Keyword(s):  
Ground Reaction Force ◽  
Reaction Force ◽  
Body Height ◽  
Force Plate ◽  
Prediction Equation ◽  
Regression Equations ◽  
Countermovement Jump ◽  
Predictive Regression ◽  
Seventh Cervical Vertebra ◽  
The Impact

Abstract Background Water jumping exercise is an alternative method to achieve maintenance of bone health and reduce exercise injuries. Clarifying the ground reaction force (GRF) of moderate and high cardiopulmonary exercise intensities for jumping movements can help quantify the impact force during different exercise intensities. Accelerometers have been explored for measuring skeletal mechanical loading by estimating the GRFs. Predictive regression equations for GRF using ACC on land have already been developed and performed outside laboratory settings, whereas a predictive regression equation for GRF in water exercises is not yet established. The purpose of this study was to determine the best accelerometer wear-position for three exercise intensities and develop and validate the ground reaction force (GRF) prediction equation. Methods Twelve healthy women (23.6 ± 1.83 years, 158.2 ± 5.33 cm, 53.1 ± 7.50 kg) were recruited as participants. Triaxial accelerometers were affixed 3 cm above the medial malleolus of the tibia, fifth lumbar vertebra, and seventh cervical vertebra (C7). The countermovement jump (CMJ) cadence started at 80 beats/min and increased by 5 beats per 20 s to reach 50%, 65%, and 80% heart rate reserves, and then participants jumped five more times. One-way repeated analysis of variance was used to determine acceleration differences among wear-positions and exercise intensities. Pearson’s correlation was used to determine the correlation between the acceleration and GRF per body weight on land (GRFVLBW). Backward regression analysis was used to generate GRFVLBW prediction equations from full models with C7 acceleration (C7 ACC), age, percentage of water deep divided by body height (PWDH), and bodyweight as predictors. Paired t-test was used to determine GRFVLBW differences between values from the prediction equation and force plate measurement during validation. Lin’s CCC and Bland–Altman plots were used to determine the agreement between the predicted and force plate-measured GRFVLBW. Results The raw full profile data for the resultant acceleration showed that the acceleration curve of C7 was similar to that of GRFv. The predicted formula was − 1.712 + 0.658 * C7ACC + 0.016 * PWDH + 0.008 * age + 0.003*weight. Lin’s CCC score was 0.7453, with bias of 0.369%. Conclusion The resultant acceleration measured at C7 was identified as the valid estimated GRFVLBW during CMJ in water.

scholarly journals Lower Limb Joint Kinetics During Moderately Sloped Running

2010 ◽  
Vol 45 (1) ◽  
pp. 16-21 ◽  
Author(s):  
Gaurav Telhan ◽  
Jason R. Franz ◽  
Jay Dicharry ◽  
Robert P. Wilder ◽  
Patrick O. Riley ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Ground Reaction Force ◽  
Injury Risk ◽  
Reaction Force ◽  
Surface Slope ◽  
Joint Moments ◽  
Joint Kinetics ◽  
3 Dimensional ◽  
Modifiable Factors ◽  
The Impact

Abstract Context: Knowledge of the kinetic changes that occur during sloped running is important in understanding the adaptive gait-control mechanisms at work and can provide additional information about the poorly understood relationship between injury and changes in kinetic forces in the lower extremity. A study of these potential kinetic changes merits consideration, because training and return-to-activity programs are potentially modifiable factors for tissue stress and injury risk. Objective: To contribute further to the understanding of hill running by quantifying the 3-dimensional alterations in joint kinetics during moderately sloped decline, level, and incline running in a group of healthy runners. Design: Crossover study. Setting: Three-dimensional motion analysis laboratory. Patients or Other Participants: Nineteen healthy young runners/joggers (age  =  25.3 ± 2.5 years). Intervention(s): Participants ran at 3.13 m/s on a treadmill under the following 3 different running-surface slope conditions: 4° decline, level, and 4° incline. Main Outcome Measure(s): Lower extremity joint moments and powers and the 3 components of the ground reaction force. Results: Moderate changes in running-surface slope had a minimal effect on ankle, knee, and hip joint kinetics when velocity was held constant. Only changes in knee power absorption (increased with decline-slope running) and hip power (increased generation on incline-slope running and increased absorption on decline-slope running in early stance) were noted. We observed an increase only in the impact peak of the vertical ground reaction force component during decline-slope running, whereas the nonvertical components displayed no differences. Conclusions: Running style modifications associated with running on moderate slopes did not manifest as changes in 3-dimensional joint moments or in the active peaks of the ground reaction force. Our data indicate that running on level and moderately inclined slopes appears to be a safe component of training regimens and return-to-run protocols after injury.

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