Biomechanics

The use of forearm and palm supports has been associated with lower neck and shoulder muscle activity as well as reduced musculoskeletal discomfort during keyboard use, however, few studies have investigated their effect during computer mouse use. Eight men and eight women completed several computer mousing tasks in six arm support conditions: Forearm Support, Flat Palm Support, Raised Palm Support, Forearm + Flat Palm Support, Forearm + Raised Palm Support, and No Support. Concurrently, an infrared three-dimensional motion analysis system measured postures, six-degree-of-freedom force-torque sensors measured applied forces & torques, and surface electromyography measured muscle activity. The use of forearm support compared to the no support condition was significantly associated with less shoulder muscle activity & torque, and the raised palm support was associated with less wrist extension. Forearm supports reduced shoulder flexion torque by 90% compared to no support. The use of either support also resulted in lower applied forces to the mouse pad. Participants reported less musculoskeletal discomfort when using a support. These results provide recommendations for office workstation setup and inform ergonomists of effective ways to reduce musculoskeletal exposures.

Thumb interaction is a primary technique used to operate small handheld devices such as smartphones. Despite the different techniques involved in operating a handheld device compared to a personal computer, the keyboard layouts for both devices are similar. A handheld device keyboard that considers the physical capabilities of the thumb may improve user experience. We developed and applied a design evaluation tool for different geometries of the QWERTY keyboard using a performance evaluation model. The model utilizes previously collected data on thumb motor performance and posture for different tap locations and thumb movement directions. We calculated a performance index (PITOT, 0 is worst and 2 is best) for 663 designs consisting in different combinations of three variables: the keyboard's radius of curvature (R) (mm), orientation (O) (°), and vertical location on the screen (L). The current standard keyboard performed poorly (PITOT = 0.28) compared to other designs considered. Keyboard location (L) contributed to the greatest variability in performance out of the three design variables, suggesting that designers should modify this variable first. Performance was greatest for designs in the middle keyboard location. In addition, having a slightly upward curve (R = -20 mm) and orientated perpendicular to the thumb's long axis (O = -20°) improved performance to PITOT = 1.97. Poorest performances were associated with placement of the keyboard's spacebar in the bottom right corner of the screen (e.g., the worst was for R = 20 mm, O = 40°, L =  Bottom (PITOT = 0.09)). While this evaluation tool can be used in the design process as an ergonomic reference to promote user motor performance, other design variables such as visual access and usability still remain unexplored.

Osteoarthritis (OA) is the most common form of arthritis worldwide. It results in chronic pain, functional limitations, and significant social and economic burdens. Obesity rates in the developed world are rapidly increasing, leading to warnings of an obesity epidemic. Obesity is associated with increased rates of OA. Traditionally, this increased prevalence was attributed to biomechanical factors including increased joint loading and altered joint dynamics due to the physical burden of obesity. However, a number of factors, including the increased prevalence of OA in non-weight-bearing joints in obese individuals and the increasing awareness of adipose tissue as a functional endocrine organ rather than an inert storage substance, have led to a reappraisal of this viewpoint. Adipose tissue secretes a number of adipokines and cytokines with both local and systemic effects. In addition, adipose tissue has the potential to stimulate a systemic inflammatory state. Differential expression of microRNAs in obese and non-obese osteoarthritic patients has been demonstrated. The potential impact of adipokines on the adipose inflammatory pathway in obese individuals is being actively explored. The traditional view of OA as a mechanical wear-and-tear disease is being revolutionised by the discovery of the key roles of inflammation and cytokines in this most common of joint diseases.

El propósito del presente trabajo, consiste en
conocer la forma en que se distribuyen los
esfuerzos que generan las cargas, comúnmente
presentes en una vena de cuerpo humano,
utilizando un modelo geométrico creado con
splines, mediante la obtención de imágenes por
medio de un tomógrafo axial computarizado,
para a su vez construir un modelo 3D con el
software Rhinoceros, y posteriormente
analizarlo en un software de elemento finito,
donde se utiliza un modelo de comportamiento
mecánico isotrópico con constantes
experimentales, en lugar de uno anisotrópico,
con la finalidad de poder simplificar el modelo.

Biomimetic leg designs often appear to be arbitrarily chosen. To make a more objective choice regarding biomimetic leg configuration for small canine-inspired robots, we compare one hind leg to the same leg arranged in a different orientation, and show that the less biomimetic leg provides better performance. This differently-oriented leg design, which we call “transverse-mirrored” was more efficient and faster, both in simulation and experiment even though both leg configurations used the same passive and active components, rest angles, and monoarticular knee spring. In experiments the normal configuration had a maximum speed of 0.33 m·s−1 and a specific resistance of 5.1. Conversely, the less biomimetic transverse-mirrored configuration had a maximum speed of 0.4 m·s−1 and specific resistance of 3.9. Therefore the transverse-mirrored leg's best performance yields a 21% increase in speed and 24% decrease in specific resistance when compared to the best performance achieved in the normal biomimetic leg. The major underlying reason is that the knee spring engages more readily in the transverse-mirrored configuration, resulting in this faster and more efficient locomotion. The conclusion is that simply copying from nature does not lead to optimal performance and that insight into the role played by passive design components on natural locomotory dynamics is important.