Littérature scientifique sur le sujet « STIFFNESS BALANCE »

Winter, David A., Aftab E. Patla, Francois Prince, Milad Ishac, and Krystyna Gielo-Perczak. Stiffness control of balance in quiet standing. J. Neurophysiol. 80: 1211–1221, 1998. Our goal was to provide some insights into how the CNS controls and maintains an upright standing posture, which is an integral part of activities of daily living. Although researchers have used simple performance measures of maintenance of this posture quite effectively in clinical decision making, the mechanisms and control principles involved have not been clear. We propose a relatively simple control scheme for regulation of upright posture that provides almost instantaneous corrective response and reduces the operating demands on the CNS. The analytic model is derived and experimentally validated. A stiffness model was developed for quiet standing. The model assumes that muscles act as springs to cause the center-of-pressure (COP) to move in phase with the center-of-mass (COM) as the body sways about some desired position. In the sagittal plane this stiffness control exists at the ankle plantarflexors, in the frontal plane by the hip abductors/adductors. On the basis of observations that the COP-COM error signal continuously oscillates, it is evident that the inverted pendulum model is severely underdamped, approaching the undamped condition. The spectrum of this error signal is seen to match that of a tuned mass, spring, damper system, and a curve fit of this “tuned circuit” yields ωn the undamped natural frequency of the system. The effective stiffness of the system, K e , is then estimated from K e = Iω2 n, and the damping B is estimated from B = BW × I, where BW is the bandwidth of the tuned response (in rad/s), and I is the moment of inertia of the body about the ankle joint. Ten adult subjects were assessed while standing quietly at three stance widths: 50% hip-to-hip distance, 100 and 150%. Subjects stood for 2 min in each position with eyes open; the 100% stance width was repeated with eyes closed. In all trials and in both planes, the COP oscillated virtually in phase (within 6 ms) with COM, which was predicted by a simple 0th order spring model. Sway amplitude decreased as stance width increased, and K e increased with stance width. A stiffness model would predict sway to vary as K −0.5 e . The experimental results were close to this prediction: sway was proportional to K −0.55 e . Reactive control of balance was not evident for several reasons. The visual system does not appear to contribute because no significant difference between eyes open and eyes closed results was found at 100% stance width. Vestibular (otolith) and joint proprioceptive reactive control were discounted because the necessary head accelerations, joint displacements, and velocities were well below reported thresholds. Besides, any reactive control would predict that COP would considerably lag (150–250 ms) behind the COM. Because the average COP was only 4 ms delayed behind the COM, reactive control was not evident; this small delay was accounted for by the damping in the tuned mechanical system.

Our previously published engaged leg model shows how stiffness plays complex multicausal roles in balance. In one role, it is crucial to stability, with task contingent influences over balance. In another, it overcomes viscous drag. Task-dependent stiffness alone does not explain stable balance; geometrical, invariant aspects of body biomechanics also matter. Our model is fully applicable to clinical balance pathologies involving asymmetries in movement and balance control.

This research presents new data and reanalyzed information to refute the criticisms of our model of stiffness control during quiet standing. A re-review of their references to biomechanical research on muscle ankle stiffness confirmed muscle stiffness estimates of the ankle series elastic elements that agreed closely with our estimates. A new technique is presented that directly estimates the muscle stiffness from the ankle moment (N · m) and sway angle (deg). The linear regression of 10 subjects standing quietly for 10 s estimated the stiffness (N · m/deg) to be safely above the gravitational spring. The R 2 scores for this linear regression averaged 0.92, confirming how closely the model approached a perfect spring that would have an R 2 = 1. These results confirm our model of a simple muscle stiffness control and refutes the criticisms.

The mechanical model related to the balance and stiffness characteristics of the bellows type rubber hose under internal pressure was studied. Based on the thin shell theory without considering bending moments and shear force, the equilibrium equation of the bellows type hose was established to obtain the mechanical equilibrium angle under different mechanical environments. Considering the deformation characteristics of the rope structure and the mechanical equilibrium angle of the hose, the deformation of the bellows type rubber hose was divided into two stages, including winding angle deflection and tensile deformation of fiber. Then the constitutive model of anisotropic material was introduced, and the physical equation of the bellows type hose was established to obtain the mechanical model of the balance and stiffness characteristics. According to the mechanical model, the influence of initial fiber winding angle, fiber layer thickness, the radius at the two ends of the hose, the length of hose, the curvature radius and internal pressure of hose on the balance and stiffness characteristics of hose was studied. Eventually, the structure of the hose was designed based on the mechanical model, to optimize the balance and stiffness characteristics of hose. The balance and stiffness characteristics of the optimized hose were verified by experiments. The theoretical and experimental results indicated that, the mechanical model of the balance and stiffness characteristics of the hose can be the theoretical basis for the optimization of structural parameters.

This communication addresses again the hypothesis that the stabilization of balance during quiet standing is achieved by the stiffness of ankle muscles without anticipatory active control. It is shown that a recently proposed method of estimating ankle stiffness directly from the analysis of the posturographic data is incorrect because it ignores the modulation of motoneuronal activity and grossly overestimates the real range of values in relation with the critical value of stiffness. Moreover, a new simulation study with a realistic model of ankle muscles demonstrates the mechanical instability of the system when there is no anticipatory control input. However, the simulations also suggest that in normal subjects the active stiffness mechanisms of stabilization have similar weights in determining the restoring forces that are necessary for preventing the body from falling.

Cerebral palsy is a neurodevelopmental movement disorder that affects coordination and balance. Therapeutic treatments for balance deficiencies in this population primarily focus on the musculoskeletal system, whereas the neural basis of balance impairment is often overlooked. Magnetic resonance elastography (MRE) is an emerging technique that has the ability to sensitively assess microstructural brain health through in vivo measurements of neural tissue stiffness. Using magnetic resonance elastography, we have previously measured significantly softer grey matter in children with cerebral palsy as compared with typically developing children. To further allow magnetic resonance elastography to be a clinically useful tool in rehabilitation, we aim to understand how brain stiffness in children with cerebral palsy is related to dynamic balance reaction performance as measured through anterior and posterior single-stepping thresholds, defined as the standing perturbation magnitudes that elicit anterior or posterior recovery steps. We found that global brain stiffness is significantly correlated with posterior stepping thresholds ( P = .024) such that higher brain stiffness was related to better balance recovery. We further identified specific regions of the brain where stiffness was correlated with stepping thresholds, including the precentral and postcentral gyri, the precuneus and cuneus, and the superior temporal gyrus. Identifying brain regions affected in cerebral palsy and related to balance impairment can help inform rehabilitation strategies targeting neuroplasticity to improve motor function.

After a transtibial amputation, the prosthetic foot aims at replacing the missing ankle joint. Due to alteration of proprioception and mobility, the static balance of amputees is challenging. The stiffness of most of the usual prosthetic feet cannot adapt according to the situation. Thus, the control of the user’s balance is closely related to the ankle stiffness value. The aim of this study is to evaluate both the impact of the ankle stiffness and the visual system on static balance. In order to avoid bias relative to different levels of residual proprioception among individuals, the study has been carried out on healthy subjects wearing lower limb prosthetic simulators under each foot. This configuration could be considered as a relevant model to isolate the effect of the stiffness. Eleven subjects wearing prosthetic feet with different modules were asked to remain as static as possible both with open eyes (OE) and closed eyes (CE). The center of pressure (COP) displacements and the joint angles range of motion (ROM) were experimentally assessed. The length of the major axis of the COP 95% confidence ellipse was projected on the antero-posterior direction (AP range). Linear regression models of the AP range and joint angles ROM as a function of the situation (OE and CE) and of the normalized ankle stiffness were created. A one-way analysis of variance test was performed on the model of the AP range. Linear regression coefficients and 95% confidence intervals (CI) were calculated between the AP range and the normalized ankle stiffness and between the joint angles ROM and the normalized ankle stiffness both in OE and CE. This study confirmed that static balance decreases when ankle stiffness decreases. The results also showed that a visual system alteration amplifies more significantly the decrease of static balance of people wearing prosthetic feet and has no significant influence on non-amputated subjects. The slope of the linear regression for the AP range according to the normalized ankle stiffness was equal to −9.86 (CI: −16.03, −3.69) with CE and −2.39 (CI: −4.94, 0.17) with OE. Both the normalized ankle stiffness and the visual system had a significant impact on the AP range (pvalue<0.05). The ankle stiffness is an interesting parameter as it has a high impact on the gait and on the static balance of the users and it must be controlled to properly design prosthetic feet.

Balance shafts are often used to improve the engine vibration characteristics of three-cylinder engines. The balance damping gear with a damping ring is an important part connecting the crankshaft and the balance shaft transmission. The stiffness characteristics of the damping ring and the unbalance of the gear have an important influence on its vibration suppression performance, but the coupled influence of the stiffness characteristics of the damping ring and the unbalanced characteristics of the vibration damping gear is unknown. In this paper, a multi-body dynamic bending–torsional coupling model of the transmission system of a three-cylinder engine with a balance damping gear is constructed considering the equivalent stiffness of the balance shaft support. Based on the fourth-order Runge–Kutta method, the influence laws of different rotational speeds, load torques, gear unbalance, radial stiffness and torsional stiffness of the damping ring on the vibration characteristics of the transmission system are obtained. The results show that the vibration amplitude increases linearly with the increase in the rotational speed and the amount of unbalance. As the load torque increases, the noise radiation of the system increases. The change in the equivalent torsional stiffness of the damping ring has little effect on the radial vibration suppression effect of the gear. As the equivalent radial stiffness of the damping ring increases, the vibration suppression rate decreases linearly. Combined with the calculation formula of damping ring stiffness, when the inner and outer diameters of the damping ring are relatively large, the vibration suppression performance decreases sharply with the increase in the thickness of the damping ring. Therefore, in order to achieve a better vibration attenuation effect, the inner to outer diameter ratio of the damping ring should be given priority in the design of the damping gear. Thus, the thickness of the design can meet the requirements of the vibration attenuation performance and a vibration attenuation of more than 90% of the radial vibration can be achieved. The model of the damping ring size and the vibration suppression effect established based on the method presented in this paper can be used to guide the design of balance damping gears.

Objective: This study aimed to assess if external focus instructions result in greater improvements in motor skill and automaticity compared to internal focus instructions in stroke patients. Design: Double-blind randomized controlled trial. Setting: Inpatient stroke rehabilitation unit. Subjects: A total of 63 stroke patients (Meanage = 59.6 ± 10.7 years; Meandays since stroke = 28.5 ± 16.6; MedianFunctional Ambulation Categories = 4). Interventions: Patients were randomly assigned to an internal ( N = 31) or external ( N = 32) focus instruction group. Both groups practiced a balance board stabilization task, three times per week, for three weeks. Balance performance was assessed at baseline, and after one and three weeks of practice. Main measures: Primary outcome was the threshold stiffness (Nm/rad) at which patients could stay balanced. Secondary outcomes were patients’ sway (root-mean-square error in degrees) at the baseline threshold stiffness under single- and dual-task conditions, and their performance on the Timed Up and Go Test and Utrecht Scale for Evaluation of Rehabilitation. Results: Both groups achieved similar improvements in threshold stiffness (∆= 27.1 ± 21.1 Nm/rad), and single- (∆= 1.8 ± 2.3° root-mean-square error) and dual-task sway (∆= 1.7 ± 2.1° root-mean-square error) after three weeks of practice. No differences were found in improvements in clinical tests of balance and mobility. Patients with comparatively good balance and sensory function, and low attention capacity showed greatest improvements with external focus instructions. Conclusion: External focus instructions did not result in greater improvement in balance skill in stroke patients compared to internal focus instructions. Results suggest that tailoring instructions to the individual stroke patient may result in optimal improvements in motor skill.

Turbulence is a major factor limiting the achievement of better tokamak performance as it enhances the transport of particles, momentum and heat which hinders the foremost objective of tokamaks. Hence, understanding and possibly being able to control turbulence in tokamaks is of paramount importance, not to mention our intellectual curiosity of it. We take the first step by making measurements of turbulence using the 2D ($8$ radial $imes$ $4$ poloidal channels) beam emission spectroscopy (BES) system on the Mega Amp Spherical Tokamak (MAST). Measured raw data are statistically processed, generating spatio-temporal correlation functions to obtain the physical characteristics of the turbulence such as spatial and temporal correlation lengths as well as its motion. The reliability of statistical techniques employed in this work is examined by generating and utilizing synthetic 2D BES data. The apparent poloidal velocity of fluctuating density patterns is estimated using the cross-correlation time delay method. The experimental results indicate that the poloidal motion of fluctuating density patterns in the lab frame arises because the patterns are advected by the strong toroidal plasma flows while the patterns are aligned with the background magnetic fields which are not parallel to the flows. Furthermore, various time scales associated with the turbulence are calculated using statistically estimated spatial correlation lengths and correlation times of turbulence. We find that turbulence correlation time, the drift time associated with ion temperature or density gradients, the ion streaming time along the magnetic field line and the magnetic drift time are comparable and possibly scale together suggesting that the turbulence, determined by the local equilibrium, is critically balanced. Finally, we argue that we have produced a critical manifold in the experimentally obtained local equilibrium parameter space separating dominant turbulent transport from a non-turbulent or weakly turbulent state. It shows that the inverse ion-temperature-gradient scale length is correlated inversely with $q/arepsilon$ (safety factor/inverse aspect ratio) and positively with the plasma rotational shear. Practically, this means that we can attain the stiffer ion-temperature-gradient, thus hotter plasma core, without increasing the rotational shear.

Körperliche Aktivität während der Schwangerschaft wirkt sich positiv auf die Gesundheit von Mutter und Kind aus. Trotzdem werden Schwangere häufig gewarnt, sich aufgrund der abnehmenden Muskelkraft, den nachgiebigeren Bändern und Sehnen sowie der verschlechterten Stabilität beim Sport verletzen zu können. Um Verletzungen während der Schwangerschaft vorbeugen zu können, wird in dieser Arbeit erstmalig der Einfluss von Schwangerschaft auf den Muskel-Sehnen-Komplex der unteren Extremitäten untersucht. Weiterhin werden der Effekt auf das statische Gleichgewicht und der Einsatz eines Schwangerschaftsgurtes als potentielle Präventionsmaßnahme gegen Sturzunfälle überprüft. Zur Untersuchung des Muskel-Sehnen-Komplexes wurde die Morphologie des m. vastus lateralis, die Muskelkraft der Knieextensoren und die Eigenschaften der Patellasehne am Anfang und am Ende der Schwangerschaft sowie ein halbes Jahr nach der Entbindung mittels Ultraschall und Dynamometrie analysiert. Das Gleichgewicht wurde anhand der Grenzen der Stabilität nach anterior und posterior und anhand des Körperschwankens im ruhigen Stand auf einer Kraftmessplatte bei Schwangeren in den unterschiedlichen Schwangerschaftstrimestern und bei Nicht-Schwangeren mit und ohne Schwangerschaftsgurt beurteilt. Diese Arbeit liefert relevante Erkenntnisse, die für die Beurteilung des Verletzungsrisikos von Schwangeren und für die Entwicklung geeigneter präventiver Maßnahmen nützlich sind. Es wurde zum wiederholten Male bestätigt, dass Schwangerschaft zu einer Verschlechterung der posturalen Stabilität führt. Ein Schwangerschaftsgurt stellt jedoch keine geeignete Methode zur Verbesserung der Stabilität dar. Während Muskelmorphologie und Sehnensteifigkeit keinen negativen Einfluss zeigen, könnte die zunehmende Sehnenruhelänge zu einer vergrößerten Gelenkbeweglichkeit beitragen und das Risiko für Verletzungen und Stürze erhöhen.
Physical activity during pregnancy has beneficial effects on maternal and fetal health. However, pregnant women are frequently cautioned when exercising since a loss in muscle strength, an increased compliance of ligaments and tendons as well as impairments in postural stability are assumed to lead to injuries in pregnant women. This thesis investigates for the first time the effect of pregnancy on the muscle-tendon unit of the lower extremities for the prevention of injuries during pregnancy. Furthermore, this thesis analyzes the effect of pregnancy on static postural stability and examines whether a maternity support belt is an appropriate method for fall prevention in pregnant women. To investigate the muscle-tendon unit, the morphology of the vastus lateralis muscle, muscle strength of the knee extensors and the properties of the patellar tendon were analyzed in the early and late stage of pregnancy as well as six months after delivery by means of ultrasound and dynamometry. Balance ability was assessed determining the limits of stability in the anterior and posterior directions and the postural sway during motionless upright standing on a force plate in pregnant women in different trimesters of pregnancy and in non-pregnant women with and without maternity support belt. This thesis provides relevant evidence for the assessment of the risk of injury in pregnant women and the development of appropriate prevention strategies. It confirmed that pregnancy is accompanied by impaired postural stability. However, a maternity support belt is not an appropriate method to improve stability. While muscle morphology and tendon stiffness were not negatively affected during pregnancy, the increase in tendon rest length might contribute to an increased joint mobility that may increase the fall and injury risk.

abstract: It has been repeatedly shown that females have lower stability and increased risk of ankle injury when compared to males participating in similar sports activities (e.g., basketball and soccer), yet sex differences in neuromuscular control of the ankle, including the modulation of ankle stiffness, and their contribution to stability remain unknown. To identify sex differences in human ankle stiffness, this study quantified 2- dimensional (2D) ankle stiffness in 20 young, healthy men and 20 young, healthy women during upright standing over a range of tasks, specifically, ankle muscle co-contraction tasks (4 levels up to 20% maximum voluntary co-contraction of ankle muscles), weight-bearing tasks (4 levels up to 90% of body weight), and ankle torque generation tasks accomplished by maintaining offset center-of-pressure (5 levels up to +6 cm to the center-of-pressure during quiet standing). A dual-axial robotic platform, capable of perturbing the ankle in both the sagittal and frontal planes and measuring the corresponding ankle torques, was used to reliably quantify the 2D ankle stiffness during upright standing. In all task conditions and in both planes of ankle motion, ankle stiffness in males was consistently greater than that in females. Among all 26 experimental conditions, all but 2 conditions in the frontal plane showed statistically significant sex differences. Further analysis on the normalized ankle stiffness scaled by weight times height suggests that while sex differences in ankle stiffness in the sagittal plane could be explained by sex differences in anthropometric factors as well as neuromuscular factors, the differences in the frontal plane could be mostly explained by anthropometric factors. This study also demonstrates that the sex differences in the sagittal plane were significantly higher as compared to those in the frontal plane. The results indicate that females have lower ankle stiffness during upright standing thereby providing the neuromuscular basis for further investigations on the correlation of ankle stiffness and the higher risk of ankle injury in females.
Dissertation/Thesis
Masters Thesis Biomedical Engineering 2020

In present scenario buildings with floating column is a typical feature in the modern multistory construction in urban India. Such features are highly undesirable in building built in seismically active areas. This study highlights the importance of explicitly recognizing the presence of the floating column in the analysis of building. Alternate measures, involving stiffness balance of the first storey and the storey above, are proposed to reduce the irregularity introduced by the floating columns. The study is carried out on a building with floating columns. The plan layout of the building is shown in the figure. The building considered is a residential building having G+9. Height of each storey is kept same as other prevalent data.

abstract: The human ankle is a vital joint in the lower limb of the human body. As the point of interaction between the human neuromuscular system and the physical world, the ankle plays important role in lower extremity functions including postural balance and locomotion . Accurate characterization of ankle mechanics in lower extremity function is essential not just to advance the design and control of robots physically interacting with the human lower extremities but also in rehabilitation of humans suffering from neurodegenerative disorders. In order to characterize the ankle mechanics and understand the underlying mechanisms that influence the neuromuscular properties of the ankle, a novel multi-axial robotic platform was developed. The robotic platform is capable of simulating various haptic environments and transiently perturbing the ankle to analyze the neuromechanics of the ankle, specifically the ankle impedance. Humans modulate ankle impedance to perform various tasks of the lower limb. The robotic platform is used to analyze the modulation of ankle impedance during postural balance and locomotion on various haptic environments. Further, various factors that influence modulation of ankle impedance were identified. Using the factors identified during environment dependent impedance modulation studies, the quantitative relationship between these factors, namely the muscle activation of major ankle muscles, the weight loading on ankle and the torque generation at the ankle was analyzed during postural balance and locomotion. A universal neuromuscular model of the ankle that quantitatively relates ankle stiffness, the major component of ankle impedance, to these factors was developed. This neuromuscular model is then used as a basis to study the alterations caused in ankle behavior due to neurodegenerative disorders such as Multiple Sclerosis and Stroke. Pilot studies to validate the analysis of altered ankle behavior and demonstrate the effectiveness of robotic rehabilitation protocols in addressing the altered ankle behavior were performed. The pilot studies demonstrate that the altered ankle mechanics can be quantified in the affected populations and correlate with the observed adverse effects of the disability. Further, robotic rehabilitation protocols improve ankle control in affected populations as seen through functional improvements in postural balance and locomotion, validating the neuromuscular approach for rehabilitation.
Dissertation/Thesis
Doctoral Dissertation Mechanical Engineering 2020

碩士
國立臺灣師範大學
運動科學研究所
98
Purpose ：To understand the effect of four different kinds of stiffness and three different swing-weight on swing-velocity, ball-velocity and coefficient of restitution. The result of the study will be taken as index to the selection and design of badminton racket in the future. Methods: Two experiments were conducted in the study; In the first experiment, the ball was served and then collided the racket; in the second experiment, the ball is fastened with clamping, hanging in the air, and hit by players. The results were recorded by 10000 Hz high speed video camera, and analyzed by video analysis software, which helped researcher to compare swing velocity and ball velocity between pre-test and post-test. Statistical analysis were conducted by two-way ANOVA to examine the effects of stiffness and swing-weight on swing-velocity, ball-velocity and coefficient of restitution. The significant level was set at α&lt;.05. Results: In the group impacted by server, the coefficient of restitution was in direct proportion to impact velocity, and the coefficient of restitution of middle swing weight was significantly higher than that of low swing weight. In the group hit by player, the swing velocity was in reverse proportion to swing weight, and the swing velocity of low swing weight was significantly faster than that of middle swing weight. Ball velocity was effected by the stiffness of the racket when swing velocity exceed 90 km; the Swing Velocity of high swing weight is slow, but its COR was higher than those of low swing weight and middle swing weight. Conclusion: The swing weight that significantly impacted on swing velocity, ball velocity and COR, and the influence of stiffness is comparatively less than swing weight. The users and designers would be advised to choose the racket with low swing weight in order to increase swing velocity, or high swing weight in order to increase COR.

This work focuses on efficient modelling and adaptive control of friction damping in bladed disks. To efficiently simulate the friction contact, a full-3D time-discrete contact model is reformulated and an analytical expression for the Jacobian matrix is derived that reduces the computation time drastically with respect to the classical finite difference method. The developed numerical solver is applied on bladed disks with shroud contact and the advantage of full-3D contact model compared to a quasi-3D contact model is presented. The developed numerical solver is also applied on bladed disks with strip damper and multiple friction contacts and obtained results are discussed. Furthermore, presence of higher harmonics in the nonlinear contact forces is analyzed and their effect on the excitation of the different nodal diameters of the bladed disk are systematically presented. The main parameters that influence the effectiveness of friction damping in bladed disks are engine excitation order,  contact stiffnesses,  friction coefficient, relative motion at the friction interface and the normal contact load. Due to variation in these parameters during operation, the obtained friction damping in practice may differ from the optimum value. Therefore, to control the normal load adaptively that will lead to an optimum damping in the system despite these variations, use of magnetostrictive actuator is proposed. The magnetostrictive material that develops an internal strain under the influence of an external magnetic field is employed to increase and decrease the normal contact load. A linearized model of the magnetostrictive actuator is used to characterize the magnetoelastic behavior of the actuator.  A nonlinear static contact analysis of the bladed disk reveals that a change of normal load more than 700 N can be achieved using a reasonable size of the actuator. This will give a very good control on friction damping once applied in practice.

QC 20170310

TurboPower

Bones are multifunctional passive organs of movement that supports soft tissue and directly attached muscles. They also protect internal organs and are a reserve of calcium, phosphorus and magnesium. Each bone is covered with periosteum, and the adjacent bone surfaces are covered by articular cartilage. Histologically, the bone is an organ composed of many different tissues. The main component is bone tissue (cortical and spongy) composed of a set of bone cells and intercellular substance (mineral and organic), it also contains fat, hematopoietic (bone marrow) and cartilaginous tissue. Bones are a tissue that even in adult life retains the ability to change shape and structure depending on changes in their mechanical and hormonal environment, as well as self-renewal and repair capabilities. This process is called bone turnover. The basic processes of bone turnover are: • bone modeling (incessantly changes in bone shape during individual growth) following resorption and tissue formation at various locations (e.g. bone marrow formation) to increase mass and skeletal morphology. This process occurs in the bones of growing individuals and stops after reaching puberty • bone remodeling (processes involve in maintaining bone tissue by resorbing and replacing old bone tissue with new tissue in the same place, e.g. repairing micro fractures). It is a process involving the removal and internal remodeling of existing bone and is responsible for maintaining tissue mass and architecture of mature bones. Bone turnover is regulated by two types of transformation: • osteoclastogenesis, i.e. formation of cells responsible for bone resorption • osteoblastogenesis, i.e. formation of cells responsible for bone formation (bone matrix synthesis and mineralization) Bone maturity can be defined as the completion of basic structural development and mineralization leading to maximum mass and optimal mechanical strength. The highest rate of increase in pig bone mass is observed in the first twelve weeks after birth. This period of growth is considered crucial for optimizing the growth of the skeleton of pigs, because the degree of bone mineralization in later life stages (adulthood) depends largely on the amount of bone minerals accumulated in the early stages of their growth. The development of the technique allows to determine the condition of the skeletal system (or individual bones) in living animals by methods used in human medicine, or after their slaughter. For in vivo determination of bone properties, Abstract 10 double energy X-ray absorptiometry or computed tomography scanning techniques are used. Both methods allow the quantification of mineral content and bone mineral density. The most important property from a practical point of view is the bone’s bending strength, which is directly determined by the maximum bending force. The most important factors affecting bone strength are: • age (growth period), • gender and the associated hormonal balance, • genotype and modification of genes responsible for bone growth • chemical composition of the body (protein and fat content, and the proportion between these components), • physical activity and related bone load, • nutritional factors: – protein intake influencing synthesis of organic matrix of bone, – content of minerals in the feed (CA, P, Zn, Ca/P, Mg, Mn, Na, Cl, K, Cu ratio) influencing synthesis of the inorganic matrix of bone, – mineral/protein ratio in the diet (Ca/protein, P/protein, Zn/protein) – feed energy concentration, – energy source (content of saturated fatty acids - SFA, content of polyun saturated fatty acids - PUFA, in particular ALA, EPA, DPA, DHA), – feed additives, in particular: enzymes (e.g. phytase releasing of minerals bounded in phytin complexes), probiotics and prebiotics (e.g. inulin improving the function of the digestive tract by increasing absorption of nutrients), – vitamin content that regulate metabolism and biochemical changes occurring in bone tissue (e.g. vitamin D3, B6, C and K). This study was based on the results of research experiments from available literature, and studies on growing pigs carried out at the Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences. The tests were performed in total on 300 pigs of Duroc, Pietrain, Puławska breeds, line 990 and hybrids (Great White × Duroc, Great White × Landrace), PIC pigs, slaughtered at different body weight during the growth period from 15 to 130 kg. Bones for biomechanical tests were collected after slaughter from each pig. Their length, mass and volume were determined. Based on these measurements, the specific weight (density, g/cm3) was calculated. Then each bone was cut in the middle of the shaft and the outer and inner diameters were measured both horizontally and vertically. Based on these measurements, the following indicators were calculated: • cortical thickness, • cortical surface, • cortical index. Abstract 11 Bone strength was tested by a three-point bending test. The obtained data enabled the determination of: • bending force (the magnitude of the maximum force at which disintegration and disruption of bone structure occurs), • strength (the amount of maximum force needed to break/crack of bone), • stiffness (quotient of the force acting on the bone and the amount of displacement occurring under the influence of this force). Investigation of changes in physical and biomechanical features of bones during growth was performed on pigs of the synthetic 990 line growing from 15 to 130 kg body weight. The animals were slaughtered successively at a body weight of 15, 30, 40, 50, 70, 90, 110 and 130 kg. After slaughter, the following bones were separated from the right half-carcass: humerus, 3rd and 4th metatarsal bone, femur, tibia and fibula as well as 3rd and 4th metatarsal bone. The features of bones were determined using methods described in the methodology. Describing bone growth with the Gompertz equation, it was found that the earliest slowdown of bone growth curve was observed for metacarpal and metatarsal bones. This means that these bones matured the most quickly. The established data also indicate that the rib is the slowest maturing bone. The femur, humerus, tibia and fibula were between the values of these features for the metatarsal, metacarpal and rib bones. The rate of increase in bone mass and length differed significantly between the examined bones, but in all cases it was lower (coefficient b <1) than the growth rate of the whole body of the animal. The fastest growth rate was estimated for the rib mass (coefficient b = 0.93). Among the long bones, the humerus (coefficient b = 0.81) was characterized by the fastest rate of weight gain, however femur the smallest (coefficient b = 0.71). The lowest rate of bone mass increase was observed in the foot bones, with the metacarpal bones having a slightly higher value of coefficient b than the metatarsal bones (0.67 vs 0.62). The third bone had a lower growth rate than the fourth bone, regardless of whether they were metatarsal or metacarpal. The value of the bending force increased as the animals grew. Regardless of the growth point tested, the highest values were observed for the humerus, tibia and femur, smaller for the metatarsal and metacarpal bone, and the lowest for the fibula and rib. The rate of change in the value of this indicator increased at a similar rate as the body weight changes of the animals in the case of the fibula and the fourth metacarpal bone (b value = 0.98), and more slowly in the case of the metatarsal bone, the third metacarpal bone, and the tibia bone (values of the b ratio 0.81–0.85), and the slowest femur, humerus and rib (value of b = 0.60–0.66). Bone stiffness increased as animals grew. Regardless of the growth point tested, the highest values were observed for the humerus, tibia and femur, smaller for the metatarsal and metacarpal bone, and the lowest for the fibula and rib. Abstract 12 The rate of change in the value of this indicator changed at a faster rate than the increase in weight of pigs in the case of metacarpal and metatarsal bones (coefficient b = 1.01–1.22), slightly slower in the case of fibula (coefficient b = 0.92), definitely slower in the case of the tibia (b = 0.73), ribs (b = 0.66), femur (b = 0.59) and humerus (b = 0.50). Bone strength increased as animals grew. Regardless of the growth point tested, bone strength was as follows femur > tibia > humerus > 4 metacarpal> 3 metacarpal> 3 metatarsal > 4 metatarsal > rib> fibula. The rate of increase in strength of all examined bones was greater than the rate of weight gain of pigs (value of the coefficient b = 2.04–3.26). As the animals grew, the bone density increased. However, the growth rate of this indicator for the majority of bones was slower than the rate of weight gain (the value of the coefficient b ranged from 0.37 – humerus to 0.84 – fibula). The exception was the rib, whose density increased at a similar pace increasing the body weight of animals (value of the coefficient b = 0.97). The study on the influence of the breed and the feeding intensity on bone characteristics (physical and biomechanical) was performed on pigs of the breeds Duroc, Pietrain, and synthetic 990 during a growth period of 15 to 70 kg body weight. Animals were fed ad libitum or dosed system. After slaughter at a body weight of 70 kg, three bones were taken from the right half-carcass: femur, three metatarsal, and three metacarpal and subjected to the determinations described in the methodology. The weight of bones of animals fed aa libitum was significantly lower than in pigs fed restrictively All bones of Duroc breed were significantly heavier and longer than Pietrain and 990 pig bones. The average values of bending force for the examined bones took the following order: III metatarsal bone (63.5 kg) <III metacarpal bone (77.9 kg) <femur (271.5 kg). The feeding system and breed of pigs had no significant effect on the value of this indicator. The average values of the bones strength took the following order: III metatarsal bone (92.6 kg) <III metacarpal (107.2 kg) <femur (353.1 kg). Feeding intensity and breed of animals had no significant effect on the value of this feature of the bones tested. The average bone density took the following order: femur (1.23 g/cm3) <III metatarsal bone (1.26 g/cm3) <III metacarpal bone (1.34 g / cm3). The density of bones of animals fed aa libitum was higher (P<0.01) than in animals fed with a dosing system. The density of examined bones within the breeds took the following order: Pietrain race> line 990> Duroc race. The differences between the “extreme” breeds were: 7.2% (III metatarsal bone), 8.3% (III metacarpal bone), 8.4% (femur). Abstract 13 The average bone stiffness took the following order: III metatarsal bone (35.1 kg/mm) <III metacarpus (41.5 kg/mm) <femur (60.5 kg/mm). This indicator did not differ between the groups of pigs fed at different intensity, except for the metacarpal bone, which was more stiffer in pigs fed aa libitum (P<0.05). The femur of animals fed ad libitum showed a tendency (P<0.09) to be more stiffer and a force of 4.5 kg required for its displacement by 1 mm. Breed differences in stiffness were found for the femur (P <0.05) and III metacarpal bone (P <0.05). For femur, the highest value of this indicator was found in Pietrain pigs (64.5 kg/mm), lower in pigs of 990 line (61.6 kg/mm) and the lowest in Duroc pigs (55.3 kg/mm). In turn, the 3rd metacarpal bone of Duroc and Pietrain pigs had similar stiffness (39.0 and 40.0 kg/mm respectively) and was smaller than that of line 990 pigs (45.4 kg/mm). The thickness of the cortical bone layer took the following order: III metatarsal bone (2.25 mm) <III metacarpal bone (2.41 mm) <femur (5.12 mm). The feeding system did not affect this indicator. Breed differences (P <0.05) for this trait were found only for the femur bone: Duroc (5.42 mm)> line 990 (5.13 mm)> Pietrain (4.81 mm). The cross sectional area of the examined bones was arranged in the following order: III metatarsal bone (84 mm2) <III metacarpal bone (90 mm2) <femur (286 mm2). The feeding system had no effect on the value of this bone trait, with the exception of the femur, which in animals fed the dosing system was 4.7% higher (P<0.05) than in pigs fed ad libitum. Breed differences (P<0.01) in the coross sectional area were found only in femur and III metatarsal bone. The value of this indicator was the highest in Duroc pigs, lower in 990 animals and the lowest in Pietrain pigs. The cortical index of individual bones was in the following order: III metatarsal bone (31.86) <III metacarpal bone (33.86) <femur (44.75). However, its value did not significantly depend on the intensity of feeding or the breed of pigs.

AbstractAdditive manufacturing (AM) methods have a growing application in different fields such as aeronautical, automotive, biomedical, and there is a huge interest towards the extension of their use. In this paper, lattice structures for AM are analysed with regards to stiffness and printability in order to verify the suitability for applications where the main requirement of efficiency in terms of stiffness has to be balanced with other needs such as weight saving, ease of manufacturing and recycling of the material. At this aim, lattice structures with high porosity unit cells and large cell size made of a recyclable material were considered with a geometrical configuration allowing 3D printing without any supports. The lattice structures considered were based on body-centred cubic (BCC) and face centred cubic (FCC) unit cell combined with cubic cell. Finally, a multi-morphology lattice structure obtained by mixing different unit cells is also proposed. The lattice structures were modelled and structurally analysed by means of finite element method (FEM), manufactured with a Fusion deposition modelling (FDM) printer and evaluated in relation to printability and dimensional accuracy. The results show that the proposed structure with mixed cells is potentially advantageous in terms of weight saving in relation to the mechanical properties.

G.T. is a 56-year-old woman with an extensive past medical history of autoimmune disorders who complained of right leg stiffness at a follow-up office visit. Her first autoimmune disease was ulcerative colitis with onset during her teen years, which prompted a total colectomy at age 19 years. She was subsequently diagnosed with Graves’ disease at age 25 years, which was treated with subtotal thyroidectomy. She developed type 1 diabetes (T1D) at age 32 years, and despite insulin pump use had an HbA1c of 9.8%. Celiac disease was diagnosed at age 55 years, but it may have been present for >10 years. Her symptoms of painful spasms of her right leg began ~10 months prior to the visit and were gradually progressive. She described leg stiffness that extended from hip to ankle and felt like “general weakness with periodic spasms.” The spasms were so severe that she was not able to bend her knee or fully extend or flex her hip, causing impaired balance and several falls. She noted that these spastic episodes were exacerbated by cold weather as well as emotional stress and anxiety, as when she was being observed. On exam, she was noted to have a markedly abnormal gait, characterized by swinging of the right leg and overcompensation of the trunk. She was unable to perform tandem walk and had impaired balance with movement but negative Romberg. Thigh palpation revealed muscle tightness. No sensory deficits were identified. The symptoms had escalated and were now debilitating.

Increased attention has been placed on the activation of the renin-angiotensin-aldosterone system (RAAS) and pathogenetic mechanisms in cardiovascular disease. Multiple studies have presented data to suggest that cardiac and arterial stiffness leading to adverse remodeling of both the heart and vasculature leads to the various pathological changes seen in coronary artery disease, heart failure (with preserved and reduced ejection fractions), hypertension and renal disease. Over-activation of the RAAS is felt to contribute to these structural and endocrinological changes through its control of the Na+/K+ balance, fluid volume, and hemodynamic stability. Subsequently, along these lines, multiple large investigations have shown that RAAS blockade contributes to prevention of both cardiovascular and renal disease. We aim to highlight the known role of the activated RAAS and provide an updated description of the mechanisms by which activation of RAAS promotes and leads to the pathogenesis of cardiovascular disease.

Computers can be a source of tremendous benefit for those with motor impairments. Enabling computer access empowers individuals, offering improved quality of life. This is achieved through greater freedom to participate in computer-based activities for education and leisure, as well as increased job potential and satisfaction. Physical impairments can impose barriers to access to information technologies. The most prevalent conditions include rheumatic diseases, stroke, Parkinson’s disease, multiple sclerosis, cerebral palsy, traumatic brain injury, and spinal injuries or disorders. Cumulative trauma disorders represent a further significant category of injury that may be specifically related to computer use. See Kroemer (2001) for an extensive bibliography of literature in this area. Symptoms relevant to computer operation include joint stiffness, paralysis in one or more limbs, numbness, weakness, bradykinesia (slowness of movement), rigidity, impaired balance and coordination, tremor, pain, and fatigue. These symptoms can be stable or highly variable, both within and between individuals. In a study commissioned by Microsoft, Forrester Research, Inc. (2003) found that one in four working-age adults has some dexterity difficulty or impairment. Jacko and Vitense (2001) and Sears and Young (2003) provide detailed analyses of impairments and their effects on computer access. There are literally thousands of alternative devices and software programs designed to help people with disabilities to access and use computers (Alliance for Technology Access, 2000; Glennen & DeCoste, 1997; Lazzaro, 1995). This article describes access mechanisms typically used by individuals with motor impairments, discusses some of the trade-offs involved in choosing an input mechanism, and includes emerging approaches that may lead to additional alternatives in the future.

Let’s continue on the self-help road to improving fibromyalgia symptoms. Suppose we are eating healthy, well-balanced meals, are no longer smoking, have learned to pace ourselves, cope with changes in the weather, are sleeping well, and have reconfigured the house. At this point, how can the body be trained to reduce pain, stiffness, and fatigue? This chapter will explore how physical, mental, and complementary modalities allow fibromyalgia patients to feel better about their bodies and minds. Therapeutic regimens that help the body and mind, whether physical therapy, yoga, acupuncture, or chiropractic methods, are all based on similar tenets of body mechanics: 1. Fibromyalgia patients will never improve unless they have good posture. Bad posture aggravates musculoskeletal pain and creates tight, stiff, sore muscles. Therefore, stretch, change positions, and have a good workstation that does not require too much leaning or reaching. 2. The way we get around is a demonstration of body mechanics. The fundamental principles of good body mechanics in fibromyalgia include using a broad base of support by distributing loads to stronger joints with a greater surface area, keeping things close to the body to provide leverage, minimizing reaching, and not putting too much pressure on the lower back. Also, don’t stay in the same position for a prolonged period of time. 3. Exercise is necessary. It improves our sense of well-being, strengthens muscles and bones, allows restful sleep, relieves stress, releases serotonin and endorphins, which decreases pain, and burns calories. 4. Don’t be shy about using supports. Whether it be an armrest, special chair, brace, wall, railing, pillow, furniture, slings, pockets, or even another person’s body, supports allow fibromyalgia patients to decrease the amount of weight or stress that would otherwise be applied to the body, producing discomfort or pain. 5. All activities should be conducive to relaxation and stress reduction, whether they be deep breathing, meditation, biofeedback, or guided imagery. There are a surprisingly large number of ways these activities can be carried out. They are discussed in the next few sections.

This paper presents the analysis of a third-order linear differential equation representing the control of a muscle-tendon system, during quiet standing. The conditions of absolute stability and critical damping are analyzed. This study demonstrates that, for small oscillations, when the gravitational effect is modeled as a destabilizing negative stiffness and muscle-tendon stiffness is positive, the energy required to reach a critically damped state is very high. The high energy consumption is a consequence of a specific high threshold of muscle-tendon stiffness needed to achieve critical damping. An approximated graphical method confirms that during a hold and release paradigm intended to perturb quiet standing, the ankle response to fall recovery is proper of a third-order system. Furthermore, a direct estimation of the muscle and tendon parameters was obtained.

This paper presents a method to compute gear mesh stiffness based on the EHD behavior by combined finite element solution of the Reynolds Equation with the elastic contact model. It is shown that this solution requires iterative procedure to balance the computed pressure profile with the external nominal transmission load. This mesh stiffness is load dependent and therefore is a nonlinear phenomenon. The nominal stiffness value is utilized to model a full (12×12) gear mesh matrix for a linear dynamic model of rotor bearing systems including gears to evaluate system dynamics and coupling between lateral/torsional vibrations.

Static balance can be applied to improve energy efficiency of mechanisms. In the field of static balancing, a lack of knowledge and design methods exists that are capable of dealing with torsional stiffness. This paper presents a design approach for statically balanced mechanisms, with the focus on mechanisms with torsional stiffness. The approach is graphical of nature and it is based on the requirement of constant potential energy. The first achievements of the presented approach are presented as five conceptual designs of four different types of mechanisms. One of them is developed further into a prototype, which has been tested. The prototype has a correlation coefficient of 0.96 and a normalized mean squared error of 0.12 with respect to the mechanical model of the conceptual design.

Neurological disorders, a concussion, or aging can extend the time-delay in the human neuromuscular balance system; this time-delay increase has been shown [5] to be an important factor contributing to the loss of balance. However, commercial balance boards used to help improve individual’s balance deficiencies do not utilize time-delay as a tunable parameter. In order to systematically study stiffness and time-delay induced instabilities in standing posture, we developed an active balance board system with controllable torsional board stiffness, as well as an added controllable feedback time-delay of the torsional board. Using this dynamical system we confirmed the presence of two distinct mechanisms of instability: insufficient stiffness leading to tipping posture and excessive time-delays leading to limit cycle oscillations. We expect that this active balance board will allow for the early identification of an increased fall-risk, especially for subjects with extended time-delays and could help provide insights into how the human postural system adapts to various environments.

Review question / Objective: To analyze the evidence on studies that have manipulated the variables that make up the strength training stimulus and its effects on motor symptoms in people with Parkinson's disease. Condition being studied: Parkinson's is a multisystemic neurodegenerative disease that affects the central nervous system and is caused by a loss of dopaminergic neurons in the compact part of the substantia nigra of the basal ganglia of the midbrain. People with Parkinson's disease (PEP) have non-motor and motor clinical symptoms. Classic motor symptoms are rest tremor, joint stiffness, bradykinesia, decreased balance, gait disturbances (speed, temporality, spatiality, support, and freezing) and decreased functional performance.

Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.