Collagen fibers are the primary load-bearing microstructural constituent of bodily soft tissues, and, when subjected to external loading, the collagen fibers reorient, uncrimp, and elongate. Specific to the atrioventricular heart valve leaflets, the collagen fiber kinematics form the basis of many constitutive models; however, some researchers claim that modeling the affine fiber kinematics (AFK) are sufficient for accurately predicting the macroscopic tissue deformations, while others state that modeling the non-affine kinematics (i.e., fiber uncrimping together with elastic elongation) is required. Experimental verification of the AFK theory has been previously performed for the mitral valve leaflets in the left-side heart; however, this same evaluation has yet to be performed for the morphologically distinct tricuspid valve (TV) leaflets in the right-side heart. In this work, we, for the first time, evaluated the AFK theory for the TV leaflets using an integrated biaxial testing-polarized spatial frequency domain imaging device to experimentally quantify the load-dependent collagen fiber reorientations for comparison to the AFK theory predictions. We found that the AFK theory generally underpredicted the fiber reorientations by 3.1°, on average, under the applied equibiaxial loading with greater disparity when the tissue was subjected to the applied non-equibiaxial loading. Furthermore, increased AFK errors were observed with increasing collagen fiber reorientations (Pearson coefficient r = -0.36, equibiaxial loading), suggesting the AFK theory is better suited for relatively smaller reorientations. Our findings suggest the AFK theory may require modification for more accurate predictions of the collagen fiber kinematics in the TV leaflets, which will be useful in refining modeling efforts for more accurate TV simulations.Strain parameters at injury prone sites of the equine third metacarpal (MC3) and proximal phalangeal (P1) bones were investigated with the aim of improving understanding of injury pathogenesis. We hypothesized that dorsal principal and shear strain patterns, magnitudes and directions would differ from proximal-to-distal; and would be similar from medial-to-lateral across each bone. Unilateral limbs from nine equine cadavers were instrumented with rosette strain gauges during limb loading to 10,500 N.  https://www.selleckchem.com/  Gauges were attached at seven dorsal sites middle MC3, distal MC3 (medial, middle, lateral) and proximal P1 (medial, middle, lateral). Outcome measures were analysed with repeated measures analysis of variance. Distal MC3 had the greatest, and proximal P1 the smallest magnitude of minimum principal and shear strains. Directions of maximum and minimum principal strain were similar at the middle and distal MC3 sites with a 20-40° direction difference compared to proximal P1. The patterns of strain magnitude and direction were similar from medial-to-lateral on distal MC3 but varied in pattern and magnitude among the P1 sites. Overall, as load reached maximum, direction of minimum principal strain became more axial in orientation, converging from opposite directions between bones, potentially maximising stability of the distal limb. The difference in strain parameters and strain ratio for adjacent anatomic sites on distal MC3 and proximal P1 was not anticipated, in light of the anatomic congruity of the metacarpophalangeal joint. Based on the predominance of shear strain across proximal P1, shear forces are likely the predominant biomechanical contributor to sagittal fractures of P1.During walking, falling is most likely to occur towards the side of the supporting lower limb during the single stance. Timely lateral redirection of the centre of mass (CoM) preceding the no-return position is necessary for balance. We analysed the curvature peaks (the inverse of the radius of curvature) of the three-dimensional path of the CoM during the entire stride. Twelve healthy adults walked on a force-sensorized treadmill at constant velocities from 0.4 to 1.2 m s-1, in 0.2 m s-1 increments. The three-dimensional displacements of the CoM, the muscular power sustaining the CoM motion with respect to the ground, and the efficiency of the pendulum-like transfer of the CoM were computed via the double integration of the ground reaction forces. The curvatures of the CoM trajectory were measured (Frenet-Serret formula). During the single stance, the curvature showed a bell-shaped increment, lasting a few tenths of a millisecond, and peaking at 365-683 m-1 (radius of 2.7-1.4 mm, respectively), the higher the walking velocity. The CoM was redirected towards the swinging lower limb. The curvature increment was sustained by muscle-driven braking of the CoM. Smoother increments of curvature (peaking at approximately 37-150 m-1), further orienting the CoM towards the leading lower limb, were observed during the double stance. The peaks of the curvatures were symmetric between the two sides. The high curvature peaks during the single stance may represent an index of dynamic balance during walking. This index might be useful for both rehabilitation and sports training purposes.
  Active video games are a new method for increasing physical activity (PA). Fully immersive virtual reality (VR) is a hardware device on which an active video game can run. Active (video games in) VR (AVR), might increase immersion, game engagement, and MVPA, thereby yielding greater exercise-related benefits, e.g., cognitive performance.
 
  We examined the induction of moderate-to-vigorous PA (MVPA) via an AVR and a sedentary VR (SVR) as well as the effects of VR play on cognitive performance, which was monitored using 2 different methods. Each of 29 sedentary college students attended three 20-min laboratory sessions (AVR, SVR, or control) in a randomized order; during the control session, they sat quietly doing nothing. A fully immersive headset was used for the 2 video game sessions. We monitored and computed participants' PA using hip-worn accelerometers (wGT3x-bt; ActiGraph, Pensacola, FL, USA) and a heart rate band (Polar H7; Polar, Kempele, Finland). After each session, the participants completed a mnemonic similarity test (MST) to measure recognition memory.