Optimizing Backrest Geometry to Minimize Interfacial Pressure Concentrations in the Mid-To-Lumbar Region During Leg Press Resistance Training

The leg press is a resistance training (RT) exercise common to both weight- and powerlifting, where spine-related injuries remain prevalent. Here, the elevated loading has the potential to result in increased pressure on vertebral bodies and introduce the risk of spinal injury. This study therefore investigates back interfacial pressure under leg press loading conditions and offers design recommendations to minimize spatial pressure concentrations. A pressure mat was used to assess the back-backrest interfacial pressure distribution of 15 subjects executing RT leg-presses at 50% bodyweight, over 16 different back-support geometries. Real-time forces, knee angles, and pressures were captured. The resulting data show that more prominent (?2.1 cm) back-supports, positioned 19cm above the seat pan typically produced greater peak pressures (41.8±7.2 kPa). Conversely, less prominent supports (~0.7 cm) generally achieved lower peak pressures (with greater distribution). Our data suggest that the most prudent choice for fixed-shape backrests to best distribute interfacial pressure on leg-press devices is to incorporate shallow convex supports (~0.7 cm), and locate them away from P=19 cm. The result is surprising as this prominence location is a common ergonomic feature. If an adjustable backrest is considered, peak pressures may be reduced by up to 26±8% (9.7±3.1 kPa) compared to flat geometries.

Study on Behavior of Steel Hoop Connections for Raw Bamboo Members

Bamboo structures have various types of connections, such as bolting and lashing. One crucial issue in bamboo structures is that the connection with bolts and nails has a lower load-carrying capacity associated with the bamboo failure resulting from the bolt or nail invading them. This paper focuses on the connection for raw bamboo members with steel hoops (BHC), of which the two semi-circular steel hoops are fastened to the raw bamboo with high-strength bolts. The sliding friction is controlled by the interfacial pressure, which can be increased by tightening the bolts. A push-out experiment on thirty-six specimens was conducted considering the following two parameters: the different surface conditions of raw bamboo (with or without the epidermis) and the different interfacial pressure. The test results mainly showed the two failure modes of specimens under certain conditions: continuous longitudinal slip after the vertical load reached the peak; and the steel hoop stuck in the bamboo skin after a period of slip. It is found that the sliding friction was controlled by the interfacial pressure, and the difference in the anti-sliding capacity between the epidermal bamboo specimen and the non-epidermal bamboo specimen was magnified with the increase of interfacial pressure. The contact stress on the surface of bamboo is approximately uniformly distributed based on the finite element analyses. The interfacial pressure can be predicted by the torque value of the digital electronic torque wrench and the equations established by mechanical analysis, respectively. Moreover, the design formulae of bearing capacity for BHC under three guaranteed rates (50%, 95%, and 99.9%) were developed based on probability theory, while the fourth design formula was derived by regression analysis. The reliability indices of the four design formulae were up to 0.07, 1.44, 3.09, and 0.97, respectively, and the resistance partial coefficients were suggested accordingly.

Contact Force Measurement Approach for Measuring Glove-Skin Interfacial Pressure

Pressure garments for medical had been widely used to enhance the recovery after an operation, for treatment of arthritis, deep vein thrombosis, leg ulcers, varicose veins or hypertrophic scars. This research aims to develop a contact force measuring approach to measure glove-skin interfacial pressure. With the aid of a force measuring sensors system, it is easier to study the efficiency of pressure garments. Besides, occupational therapists can also design a user-friendly pressure garment that is comfortable and easy to donning and doffing, especially for children. Two types of flexible force sensors were used to measure the glove-skin interfacial pressure using two types of pressure therapy gloves. Pressure therapy glove is selected to represent pressure garments. The measuring sensors were placed at three different locations on the dorsal side of the hand, and the glove-skin interfacial pressure was measured in two different postures, which is full fist and tabletop posture. It was found that different postures had led to different interfacial pressure. The glove-skin interfacial pressure was found to be greater during full fist posture compared to tabletop posture. This show that the applied glove-skin interfacial pressure is affected by postures and movement.

Developing a control framework for self-adjusting prosthetic sockets incorporating tissue injury risk estimation and Generalized Predictive Control

Purpose: To perform activities of daily living (ADL), people with lower limb amputation depend on the prosthetic socket for stability and proprioceptive feedback. Poorly fitting sockets can cause discomfort, pain, limb tissue injuries, limited device usage, and potential rejection. Semi-passively controlled adjustable socket technologies exist, but these depend upon the user’s perception to determine safe interfacial pressure levels. This paper presents a framework for automatic control of an adjustable transtibial prosthetic socket that enables active adaptation of residuum-socket interfacial loading through localized actuators, based on soft tissue injury risk estimation. Method: Using finite element analysis, local interfacial pressure vs. compressive tissue strain relationships were estimated for three anatomical actuator locations, for tissue injury risk assessment within a control structure. Generalized Predictive Control of multiple actuators was implemented to maintain interfacial pressure within estimated safe and functional limits. Results: Controller simulation predicted satisfactory dynamic performance in several scenarios, based on previous related studies. Actuation rates of 0.06 – 1.51kPa/s with 0.67% maximum overshoot, and 0.75 – 1.58kPa/s were estimated for continuous walking, and for a demonstrative loading sequence of ADL, respectively. Conclusion: The developed platform could be useful for extending recent efforts in adjustable lower limb prosthetic socket design, particularly for individuals with residuum sensory impairment.

EVALUATING THE DYNAMIC PERFORMANCE OF INTERFACIAL PRESSURE SENSORS AT A SIMULATED BODY-DEVICE INTERFACE

BACKGROUND: Pressure sensing at the body-device interface can help assess the quality of fit and function of assistive devices during physical activities and movement such as walking and running. However, the dynamic performance of various pressure sensor configurations is not well established. OBJECTIVE(S): Two common commercially available thin-film pressure sensors were tested to determine the effects of clinically relevant setup configurations focusing on loading areas, interfacing elements (i.e. ‘puck’) and calibration methods. METHODOLOGY: Testing was performed using a customized universal testing machine to simulate dynamic, mobility relevant loads at the body-device interface. Sensor performance was evaluated by analyzing accuracy and hysteresis. FINDINGS: The results suggest that sensor calibration method has a significant effect on sensor performance although the difference is mitigated by using an elastomeric loading puck. Both sensors exhibited similar performance during dynamic testing that agree with accuracy and hysteresis values reported by manufacturers and in previous studies assessing mainly static and quasi-static conditions. CONCLUSION: These findings suggest that sensor performance under mobility relevant conditions may be adequately represented via static and quasi-testing testing. This is important since static testing is much easier to apply and reduces the burden on users to verify dynamic performance of sensors prior to clinical application. The authors also recommend using a load puck for dynamic testing conditions to achieve optimal performance. Layman's Abstract Pressure sensors can be used in prosthetics to provide clinicians with data about how well a device fits and functions. However, pressure sensors are unproven when it comes to use during activities such as walking or running. This study tested two common pressure sensors in a setup that applied forces similar to walking. These findings indicate that sensor calibration affects sensor accuracy. Accuracy can be improved by applying a small puck to the sensor to spread the load more evenly. With the puck, the performance of the sensors was found to be acceptable for potential use in clinical applications. These findings also show that dynamic testing of pressure sensors may not be needed prior to clinical usage. Instead, performance can be based on static testing which is easier to do. Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/36059/27891 How To Cite: Hamilton M, Sivasambu H, Behdinan K, Andrysek J. Evaluating the dynamic performance of interfacial pressure sensors at a simulated body-device interface. Canadian Prosthetics & Orthotics Journal. 2021;Volume 4, Issue 1, No.4. https://doi.org/10.33137/cpoj.v4i1.36059 Corresponding Author: Jan Andrysek, PhD,Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, Toronto, Canada.Email: [email protected]: https://orcid.org/0000-0002-4976-1228

Study on the Relationship between Emulsion Properties and Interfacial Rheology of Sugar Beet Pectin Modified by Different Enzymes

The contribution of rheological properties and viscoelasticity of the interfacial adsorbed layer to the emulsification mechanism of enzymatic modified sugar beet pectin (SBP) was studied. The component content of each enzymatic modified pectin was lower than that of untreated SBP. Protein and ferulic acid decreased from 5.52% and 1.08% to 0.54% and 0.13%, respectively, resulting in a decrease in thermal stability, apparent viscosity, and molecular weight (Mw). The dynamic interfacial rheological properties showed that the interfacial pressure and modulus (E) decreased significantly with the decrease of functional groups (especially proteins), which also led to the bimodal distribution of particle size. These results indicated that the superior emulsification property of SBP is mainly determined by proteins, followed by ferulic acid, and the existence of other functional groups also promotes the emulsification property of SBP.

Recent Analysis on new Nanoemulgel Transdermal Drug Delivery System use for Skin Disease Treatment

Nanoemulsions have the potential in medical industries due to transparency at high droplet volume division, higher bio availability rate and expanded shelf life of drugs. The “Nano emulsion-based gel" is a very interesting transdermal delivery framework as it has double delivery control framework, i.e., nano emulsion & hydrogel. The Nano emulgel having nanosized emulsion goes from 10-100μm may quickly enter and convey dynamic substance more profound and faster. The gelling limit of this compound permits the definition of stable emulsion and creams by diminishing surface and interfacial pressure simultaneously expanding the consistency of watery stage. Regardless of the many preferred position of gels, a significant restriction is in delivery of hydrophobic medication. So to defeat this constraint, an emulsion-based methodology is being utilized to that even a hydrophobic moiety might appreciate exceptional property of gel. They have clingy causing distress, less spreading coefficient, scouring is a requirement for application to the skin, and they show the issue of solidness for detailing. Due to all these disadvantages, gels are selected for both cosmetic as well as a pharmaceutical formulation. Despite several benefits of gels, the main drawback is with the delivery of hydrophobic therapeutic moiety. So, emulgel based approach is used to overcome this drawback; by this, even a hydrophobic drug might be included and delivered successfully. When emulsions and gels are mixed than that dosage form is mentioned as emulgel. In fact, the existence of a gelling agent changes conventional emulsion into an emulgel in the water phase.

News on Baer–Nunziato-type model at pressure equilibrium

A six-equation Baer–Nunziato model at pressure equilibrium for two ideal gases is derived from a full non-equilibrium model by applying an asymptotic pressure expansion. Conditions on the interfacial pressure are provided that ensure hyperbolicity of the reduced model. Closure conditions for the relaxation terms are given that ensure consistency of the model with the second law of thermodynamics.