Dynamic Stiffness Index Research Articles

Pressure and stiffness of a new air-inflated compression wrap.

To report pressure and stiffness, in healthy volunteers, of a new compression device with an air bladder inflated by a pump to regulate pressure. The device was applied to 60 legs of 30 volunteers and set to exert different pressures of 20-50mmHg. The exerted pressure was measured in supine and standing positions and during simple physical exercises; static stiffness index, dynamic stiffness index, and walking pressure amplitudes were calculated. The exerted pressure showed a good correlation with the expected pressure at each pressure range. The stiffness indices were >10mmHg in the range of inelastic materials. The device was considered very easy to apply and use by the testing researchers. The device stiffness is in the same range as the inelastic bandages. Consequently, similar hemodynamic effectiveness could be expected but must be proved. Unlike inelastic bandages, this device was easy to apply and use.

Effects of lower limb muscle strengthening on interface pressure in older adults undergoing inelastic compression: Randomized controlled clinical trial.

To analyze the effects of lower limb muscle strengthening on interface pressure (IP), static stiffness index (SSI), dynamic stiffness index (DSI), and walking pressure amplitude (WPA) in older adults undergoing inelastic compression therapy. Forty-three healthy older adults of both sexes (Age: 66.2 ± 4.4 years) met the eligibility criteria and completed all stages of the study (Resistance Training - RT: N = 20; Control - CONT: N = 23). Body composition, strength and functional mobility of lower limbs, IP, SSI, DSI, and WPA were evaluated before and after intervention. The two-way ANOVA with repeated measures demonstrated a significant time-group interaction effect on muscular strength for 1-RM [F (1, 41) = 21.091; p ≤ 0.001], IP in the orthostatic position [F (1, 41) = 5.124; p ≤ 0.05], minimum WPA [F (1, 41) = 10.999; p ≤ 0.05], maximum WPA [F (1, 41) = 8.315; p ≤ 0.05], DSI minimum (F (1, 41) = 4.608; p ≤ 0.05), DSI maximum (F (1, 41) = 8.926; p ≤ 0.05), and on the delta DSI (F (1, 41) = 7.891; p ≤ 0.05). In RT group, the increase in lower limb muscle strength was accompanied by an increase in IP in foot dorsiflexion and plantar flexion maneuvers, both in the standing position (DSI) and during gait (WPA).

Pressure Curves, Static and Dynamic Stiffness of Different Two-Component Compression Systems for the Treatment of Chronic Edema of the Lower Limbs

Background: Compression is a cornerstone modality in edema treatment. Different types of bandages are available in clinical practice. Short-stretch bandages are commonly used; however, newer technologies such as the two-component compression system are available as well. This study assesses the pressure curves and static and dynamic stiffness (Static Stiffness Index [SSI] and Dynamic Stiffness Index [DSI]) of two different two-component compression systems, Coban and CoFlex, for edema treatment. Methods and Results: For this prospective cohort study, 12 healthy volunteers were recruited. The healthy volunteers wore both two-component compression systems for 48 hours. Pressure sensors (PicoPress®; Microlab, Italy) were placed at 10 and 25 cm above the internal malleolus and 10 pressure readings were used to obtain pressure curves. The SSI and DSI were assessed. Additionally, comfort (ICC compression questionnaire) and adverse events were assessed as well. Both two-component compression systems exert a sufficient amount of sub-bandage pressure, although CoFlex exerts systematically significantly lower pressure in comparison with Coban. This difference in sub-bandage pressure remains constant over 48 hours. Both two-component compression systems are sufficiently stiff (stiffness >15 mmHg) and remain stiff over time. Conclusions: Both two-component compression systems have pressure curves that are high enough to motivate their use in the treatment of chronic edema. Additionally, both systems were found to be comfortable and have clinically effective SSI and DSI values.

Multi-objective optimization of CFRP engine hood considering dynamic performance based on surrogate model

This paper uses a steel engine hood as a prototype to design a carbon fiber reinforced plastic (CFRP) engine hood, analyzes the dynamic performance of the engine hood and optimizes the dynamic stiffness index while considering lightweight of the structure. Taking the layer thickness of each ply orientation of the CFRP engine hood as the design variable, the optimal Latin hypercube design (Opt-LHD) method is applied for uniform sampling. Moreover, the Kriging model method and response surface model (RSM) method are used to construct the surrogate model of the total mass, equivalent dynamic stiffness of critical points, and the first-order modal frequency. Then the Non-dominated Sorting Genetic Algorithm NSGA-II is used for multi-objective optimization with the equivalent dynamic stiffness and mass of the CFRP engine hood as the optimization objective. Finally, the optimized CFRP engine hood was trial-produced and compared with the original steel engine hood. The results indicate that the optimized CFRP engine hood has better dynamic stiffness performance; furthermore, the lightweight effect reaches 24.4 %.

Dynamic Functional Stiffness Index of the Ankle Joint During Daily Living

Exploring ankle joint physiologic functional stiffness is crucial for improving the design of prosthetic feet that aim to mimic normal gait. We hypothesized that ankle joint stiffness would vary among the different activities of daily living and that the magnitude of the stiffness would indicate the degree of energy storage element sufficiency in terms of harvesting and returning energy. We examined sagittal plane ankle moment versus flexion angle curves from 12 healthy subjects during the daily activities. The slopes of these curves were assessed to find the calculated stiffness during the peak energy return and harvest phases. For the energy return and harvest phases, stiffness varied from 0.016 to 0.283 Nm/kg° and 0.025 and 0.858 Nm/kg°, respectively. The optimum stiffness during the energy return phase was 0.111 ± 0.117 Nm/kg° and during the energy harvest phase was 0.234 ± 0.327 Nm/kg°. Ankle joint stiffness varied significantly during the activities of daily living, indicating that an energy storage unit with a constant stiffness would not be sufficient in providing energy regenerative gait during all activities. The present study was directed toward the development of a complete data set to determine the torque-angle properties of the ankle joint to facilitate a better design process.

Analysis of Dynamic Stiffness of Bridge Cap‐Pile System

In order to investigate the applicability of dynamic stiffness for bridge cap‐pile system, a laboratory test was performed. A numerical model was also built for this type of system. The impact load was applied on the cap top and the dynamic stiffness was analysed. Then, the effect of the effective friction area between pile and soil was also considered. Finally, the dynamic stiffness relationship between the single pile and the cap‐pile system was also compared. The results show that the dynamic stiffness is a sensitive index and can well reflect the static characteristics of the pile at the elastic stage. There is a significant positive correlation between the vertical dynamic stiffness index and bearing capacity of the cap‐pile system in the similar formation environment. For the cap‐pile system with four piles, the dynamic stiffness is about four times as large as the single pile between 10 and 20 Hz.

Dynamic Stiffness Assessment of Construction Materials by the Resonant and Non-resonant Methods

Dynamic stiffness of pavement surfaces is a structural property related to surface vibration and traffic noise. It is one of the mechanisms involved in tire/road noise generation. An equipment for measuring dynamic stiffness was designed and built to perform in-situ nondestructive testing on road surfaces. Laboratory studies on samples are presented to compare different measurement procedures. Measurements of the dynamic stiffness were carried out by the Resonant and Non-resonant Method. Moreover, a Dynamic Stiffness Index is proposed in order to compare the stiffness of the studied samples. Construction materials with different characteristics were studied, from resilient materials for acoustic insulation to rigid materials for pavement construction. Results show that the Non-resonant Method is more suitable for dynamic stiffness measurements, since this method could be carried out on real pavements, and both, driving point and transfer functions could be measured simultaneously. Little dynamic stiffness differences were found among road construction materials, compared to those of the resilient materials. However, the presented testing procedures are able to establish differences among these materials.

A Compression Kit of a Stocking and Three Superimposed Leggings Is Easy to Don and Dose Adjustable

Forty percent of patients with chronic venous insufficiency (CVI) do not wear their indicated and prescribed compression stockings. Difficulties in donning and a feeling of constraint are the most common reasons for non-adherence. The aim was to develop a compression stocking system that is easy to don and dose adjustable. A modular compression stocking kit composed of an understocking and three superimposable leggings (SLLLs) was developed. Substocking pressures (P) at the thinnest part above the ankle (cB level) were 17 mm (understocking) + 15 + 10 + 10 mmHg (3 superimposed leggings; Hatra method). Twenty healthy subjects and 20 patients over 65 years with CVI donned the SLLL compression kit. P was measured in vivo (Picopress method) at the transition of the Achilles tendon to the calf muscle (level cB1) during rest and ankle movements (DSI; dynamic stiffness index) and compared with a strong compression stocking of 40 mmHg (S40). Twenty (20/20) patients aged over 65 with CVI (C4-6) successfully donned the SLLL compression kit without aid, compared with 12 (12/20) who were able to don the S40 without aid (p = .02). In vivo resting P at level cB1 was 34.3 mmHg (SLLL) compared with 37.3 mmHg (S40) (p = .1). The DSI was 16.1 (SLLL) compared with 17.9 (p = .79; S40; CVI group). The physical properties of the SLLL compression stocking kit correspond to the characteristics of a strong stocking at rest and exercise (DSI). The donning success rate is excellent (100%). A further potential advantage is that the SLLL leg compression kit is dose adjustable, according to indication or patient tolerance. Wearing comfort over periods of several days and clinical effectiveness need to be investigated in future trials.

Analysis of factors governing dynamic stiffness index of medical compression bandages

To identify and analyze the important factors which could influence the Dynamic Stiffness Index (DSI) of compression bandages. Using three commercially available bandages with different stiffnesses, their DSI was obtained using a prototype based on an artificial leg-segment model consisting of a wooden mannequin having a variable circumference. The effect on DSI of three major factors, bandage extensibility (ε), resting pressure (RP) and limb circumference (C) was studied. An N-way ANOVA for a fixed model was carried out to test the significance of the above major factors and their interaction effects on bandage DSI. There were significant differences (p<0.05) between the mean DSI observed at different values of ε, RP and C. It was also found that some of the factors, ε and RP, and C and RP, interfere with each other and that their interaction effects also significantly affected the DSI (p<0.05). The above major factors have a deciding influence on the DSI of the compression bandages. Understanding the influence of these factors and the effect of their interactions on the DSI could help in pre-evaluating and comparing dynamic behaviors of different compression bandages during compression management.

New method for investigating the dynamic pressure behavior of compression garment

Purpose – The paper aims to develop a system and measuring method for investigating the dynamic pressure behavior of compression garments.Design/methodology/approach – The dynamic pressure behavior measurement, realized by use of the self‐designed system, is a direct measuring method, which is based on a rigid hemisphere with five pressure sensors distributed on its surface. The dynamic pressure is measured over time under the process of fabric 3D deformation. The pressure distributions at the basic five sites are accepted as the measuring results. The dynamic stiffness index can be calculated from dynamic pressure profile and 3D deformation of compression garments.Findings – The measuring system records the pressure‐time curve and pressure‐deformation curve. The dynamic pressure stiffness index expresses the change in pressure owing to the change in elongation of compression fabrics. The pressure measuring system and the index provide much information in the field of compression garment assessment.Resear...

Impact of variation in limb shape on sub-bandage interface pressure

Sub-bandage interface pressure generated by medical compression bandages (MCB) and hosiery changes in mobile patients as they move due to the change in the limb size. However, the amount of variation in the interface pressure is dependent on the stiffness of the compression material. Researchers have proposed several indices to describe this change in interface pressure, including the static stiffness index (SSI) and the dynamic stiffness index (DSI). These indices can also be used to classify compression products. To explore the different proposed indices to describe the stiffness of a compression material and compare it to the engineering stress-strain modulus which is used for the same purpose; To estimate theoretically the change in the interface pressure which is caused by the change in the limb shape as a consequence of calf muscle activity and the associated transient variation in limb dimensions. Use Chord modulus to classify compression material; Use thin and thick cylinder wall theory to estimate the variation in the interface pressure due to changes in the limb shape secondary to muscle contraction; Use tensile test devices to obtain the Chord modulus for two different MCB at two different dynamic ranges. Chord modulus (E) describes the change in tension in a dynamic situation, and this is labelled as stiffness in the bandaging literature; Chord modulus, with the help of a mathematical model that was developed based on thick wall cylinder theory, can be used to predict the change in sub-bandage interface pressure caused by the change in limb shape secondary to calf muscle activity; Chord modulus can be used to classify bandages and describe how they will behave when they are applied to a leg. The dynamic pressure can be predicted using a simple mathematical model using Chord modulus, which can be calculated in vitro using standard tensile testing equipment. In addition, Chord modulus can be used to classify compression bandages and hosiery.

Changes in the pressure and the dynamic stiffness index of medical elastic compression stockings after having been worn for eight hours: a pilot study

There is no data available at present on the changes in the exerted pressure together with the dynamic stiffness index (DSI) of medical elastic compression stockings (MECS). The objective of this pilot study was to measure the pressure and calculate the DSI of 12 different brands of MECS before and after having been worn for eight hours. In all, 12 different commercially available brands of MECS that were divided into two categories (class I round-knitted and class II flat-knitted MECS) were tested. The pressure was measured, and the DSI of the MECS was first calculated at the B1 level before wearing in the morning and again eight hours after they had been worn. All laboratory measurements were performed using a newly developed dynamic leg-segment model. The pressure at the B1 level dropped significantly in all 12 brands of MECS after having been worn for eight hours, whereas the DSI remained unchanged. The DSI of MECS reflects an important and particularly consistent therapeutic effect. As the pressure drops during the day, the pressure amplitude or pulsations remain the same. The pressure drop may be due to fatigue of the elastic material. The DSI would therefore form a valuable indicator for prescribing the most effective MECS for the patient.

Correlation Between the Static and Dynamic Stiffness Indices of Medical Elastic Compression Stockings

Compression therapy with medical elastic compression stockings (MECS) has been used effectively for treating patients with chronic venous insufficiency for many years. To study the correlation between static stiffness and the dynamic stiffness index of 18 different brands of MECS. In all, 18 different brands of MECS were divided into 5 categories (class II round-knit, class II flat-knit, class III round-knit, class III flat-knit, and class IV flat-knit) and tested. The tension of the textile of the MECS at the B1 level was measured according to the Institut de Textile France method to calculate the static stiffness index. The dynamic pressure pulsations were measured with a newly developed dynamic pressure-determining device to calculate the dynamic stiffness index. The results showed that there was a positive correlation between the static stiffness index and the dynamic stiffness index. The dynamic stiffness indices were higher than the static stiffness indices. Although the stiffness of MECS is a further refinement to the current classification, which classifies MECS according to the pressure they exert at the B level, the dynamic stiffness index does not have any additional value over the static stiffness index as far as the classification of MECS is concerned. Either or both of these characteristics should be used to select the most suitable MECS for the patient.

Variation in the dynamic stiffness index of different types of medical elastic compression stockings

To calculate the dynamic stiffness index (DSI) of 18 different brands of medical elastic compression stockings (MECS). In all, 18 different brands of MECS that were divided into five categories (class II round-knitted, class II flat-knitted, class III round-knitted, class III flat-knitted and class IV flat-knitted MECS) were tested. The static pressure and dynamic pressure pulsations at the B1 level were measured with a newly developed dynamic pressure-determining device. The DSI was calculated. The DSI of all 18 brands of MECS showed higher values compared with the static stiffness. A wide range of dynamic stiffness indices was observed not only between all brands of MECS, but also within the five categories. The DSI of MECS is independent of the compression class and the type of knit. The variation in the DSIs between MECS is not because of any measurement error and would indicate that different therapeutic effectiveness may be expected within one compression class. Therefore, a refinement in the current classification system for MECS with other characteristics such as the DSI is warranted.

A Method for Measuring the Dynamic Behavior of Medical Compression Hosiery during Walking

BACKGROUND Compression therapy is effective in patients suffering from venous disease. This therapy has proven to be especially effective in the ambulant patient. Therefore, the dynamic behavior of the medical compression hosiery (MCH) is more important than the static one in the treatment of patients. OBJECTIVE The objective of this study was to develop a method for investigating the dynamic behavior of MCH during walking. METHODS The changes in the circumference of the lower leg equipped with a MCH are registered on a treadmill. The dynamic movement is then exactly simulated using an artificial leg-segment model equipped with the same MCH. The dynamic behavior of the MCH can thus be investigated using this artificial leg-segment model. The dynamic stiffness index can be calculated from the dynamic pressure and circumference signals. RESULTS The expansion of the MCH was only limited to the area underlying the expanding muscles and did not spread circularly. This resulted in relatively high pressure exerted by the MCH on the underlying tissues during walking. Insertion of nonelastic material into the MCH overlying the expanding muscles increased the dynamic pressure. CONCLUSIONS The active behavior of the MCH during normal walking differed considerably from its passive behavior. We defined a new characteristic of the MCH: the dynamic stiffness index based on the dynamic pressure profile. Insertion of nonelastic materials into the MCH covering overlying the expanding muscles increased the dynamic stiffness index.

A Method for Measuring the Dynamic Behavior of Medical Compression Hosiery during Walking

. Compression therapy is effective in patients suffering from venous disease. This therapy has proven to be especially effective in the ambulant patient. Therefore, the dynamic behavior of the medical compression hosiery (MCH) is more important than the static one in the treatment of patients. . The objective of this study was to develop a method for investigating the dynamic behavior of MCH during walking. . The changes in the circumference of the lower leg equipped with a MCH are registered on a treadmill. The dynamic movement is then exactly simulated using an artificial leg-segment model equipped with the same MCH. The dynamic behavior of the MCH can thus be investigated using this artificial leg-segment model. The dynamic stiffness index can be calculated from the dynamic pressure and circumference signals. The expansion of the MCH was only limited to the area underlying the expanding muscles and did not spread circularly. This resulted in relatively high pressure exerted by the MCH on the underlying tissues during walking. Insertion of nonelastic material into the MCH overlying the expanding muscles increased the dynamic pressure. The active behavior of the MCH during normal walking differed considerably from its passive behavior. We defined a new characteristic of the MCH: the dynamic stiffness index based on the dynamic pressure profile. Insertion of nonelastic materials into the MCH covering overlying the expanding muscles increased the dynamic stiffness index.