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Quantifying stair gait stability and plantar pressure in an aging community, with modifications to insoles and lighting


Listed In: Biomechanics, Gait, Other

Lower Extremity Muscle Contributions to Ground Reaction Force during a Stop-Jump Task

Females commonly use a landing technique that creates higher impact forces when contacting the ground, thus leading to higher ground reaction force (GRF) acting upon the lower extremities, leading to an increased risk of injury. The lower extremity musculature plays a critical role in absorbing the energy of these impact forces during landing. Understanding how specific muscle groups contribute to ground reaction force may offer insight to creating more advanced landing retraining protocols. The purpose of this study was to observe how lower extremity muscle groups contribute to GRFs during an unanticipated stop-jump task. 3D musculoskeletal simulations of unanticipated stop-jump tasks were completed for five healthy females. Participant-specific scaled musculoskeletal models (modified gait2392) were generated. A pseudo-inverse induced-acceleration analysis was used to determine individual muscle group contribution to 3D GRFs. Means ± standard deviations were calculated for each muscle group during the landing phase. The vasti, soleus, and the gluteus maximus muscle groups were most responsible for bodyweight support, with the vasti and the soleus being the largest contributors (375.84±88.64 N; 267.39±103.70 N, respectively). The vasti group (165.63±74.94 N) were primarily responsible for braking and propulsion. Finally, the gluteus maximus, gluteus medius, and vasti group were the major generators in producing a medially-directed GRF, with the vasti group as the largest contributor (118.05±32.83 N). The vasti, soleus, and gluteus maximus appears to be the overall largest contributors to 3D GRFs. Landing retraining protocols may want to consider targeting these muscle groups specifically to improve landing performance and decrease injury risk.
Listed In: Biomechanics, Sports Science, Other

Relationship between Range of Motion, Strength, Upper Quarter Y-balance Test and a history of Shoulder Injury among NCAA Division I Overhead Athletes

Background: Several risk factors have been identified as contributors to the development of shoulder injuries, including glenohumeral internal rotation deficit, rotator cuff weakness, and shoulder instability. However, lasting deficits of the physical characteristics among overhead athletes with a history of a shoulder injury are unknown. Objective: To compare shoulder range of motion (ROM), strength, and upper-quarter dynamic balance between collegiate overhead athletes with and without a history of a shoulder injury. Methods: 58 overhead athletes were distributed into a shoulder injury history group (n=25) and healthy group (n=33). All participants were fully participating in NCAA Division I baseball, softball, volleyball, or tennis and free of any symptoms of shoulder injuries. An investigator measured active ROM for dominant shoulder internal rotation (IR), external rotation (ER), and horizontal adduction (HAD) using a digital inclinometer. Isometric strength for dominant shoulder IR and ER at 90° of abduction was measured using a hand-held dynamometer. The upper quarter dynamic balance was assessed via the Upper Quarter Y-Balance Test (UQYBT). Results: The injury group demonstrated a lower UQYBT mean score in the superolateral direction. However, there were no statistically significant intergroup differences in shoulder ROM, strength, ER/IR strength ratio, and UQYBT in the medial direction and inferolateral direction. Conclusions: Overhead athletes with a previous history of shoulder injury had poorer UQYBT in the superolateral direction despite a lack of ongoing symptoms or deficits in function. Well-planed dynamic balance training and related strengthening exercises may be warranted for overhead athletes to improve their upper quarter functions.
Listed In: Physical Therapy, Sports Science, Other

Effects of Compliant Flooring Systems and Resident Weight on Hand Forces When Pushing Floor-Based Lifts and Wheelchairs Among Long-Term Care Staff

Listed In: Other


Listed In: Biomechanics, Gait, Other

Muscle force prediction of the lower limb compared to surface EMG at different walking speeds in individual healthy subjects.

Listed In: Biomechanics, Gait, Other

The Effects of Knee Taping Techniques on Lower Extremity Kinematics During Running

Introduction: Running is a popular form of physical activity linked to various lower extremity injuries. A commonly used technique for injury prevention and rehabilitation is taping. There is considerable research investigating running biomechanics, however, there has been limited to no research examining the effects of gender, speed, and the type of tape used on two-dimensional lower extremity kinematics. Therefore, the purpose of this pilot study was to investigate the effects of gender, speed, and tape on two-dimensional lower extremity kinematics and stride characteristics during running. Method: Eight healthy runners participated (4 males, 4 females). Taping interventions (Leukotape, Kinesio Tape, no tape) and speeds (2.35 m/s, 3.35 m/s) were randomized and lower extremity stride kinematics were obtained using the Peak Motus System at initial contact, midstance, and toe off of running. Comparisons were made using descriptive statistics. Results: Females exhibited greater hip (FIC= 164.04+1.99°; MIC= 167.54+2.12°) and knee flexion (FIC= 167.73+0.93°; MIC= 170.42+1.65°; FPK= 142.83+1.28°; MPK= 146.35+1.21°), while males had greater ankle dorsiflexion (FIC= 88.60+1.00°; MIC= 84.14+1.08°) and plantarflexion (FTO= 51.90+1.01°; MTO= 55.99+0.825°). Females spent more time in support (FCT= 0.28+0.03s; MCT= 0.26+0.02s) while males spent more time in the air (FFT= 0.45+0.02s; MFT= 0.48+0.01s). Faster speed was associated with greater hip flexion and extension (SIC= 167.57+1.95°; FIC= 164.01+2.11°; STO= 197.14+1.23°; FTO= 201.28+0.74°), peak knee flexion (SPK= 145.39+1.82°; FPK= 143.79+2.39°), and less time during contact (SIC = 0.30+0.01s; FIC= 0.25+0.00s). Conclusion: Gender and speed seem to have effects on lower extremity stride kinematics, whereas type of tape does not.
Listed In: Biomechanics, Gait, Other

One Hundred Data-Driven Haptic Texture Models and Open-Source Methods for Rendering on 3D Objects

This work introduces the Penn Haptic Texture Toolkit (HaTT), a publicly available repository of haptic texture models for use by the research community. HaTT includes 100 haptic texture and friction models, the recorded data from which the models were made, images of the textures, and the code and methods necessary to render these textures using an impedance-type haptic interface such as a SensAble Phantom Omni. This work reviews our previously developed methods for modeling haptic virtual textures, describes our technique for modeling Coulomb friction between a tooltip and a surface, discusses the adaptation of our rendering methods for display using an impedance-type haptic device, and provides an overview of the information included in the toolkit. Each texture and friction model was based on a ten-second recording of the force, speed, and high-frequency acceleration experienced by a handheld tool moved by an experimenter against the surface in a natural manner. We modeled each texture’s recorded acceleration signal as a piecewise autoregressive (AR) process and stored the individual AR models in a Delaunay triangulation as a function of the force and speed used when recording the data. Measurements of the user’s instantaneous normal force and tangential speed are used to synthesize texture vibrations in real time. These vibrations are transformed into a texture force vector that is added to the friction and normal force vectors for display to the user.
Listed In: Mechanical Engineering, Other


Eccentric training may affect the longitudinal adaptation of the muscle. Usually the muscle fiber lengthening during eccentric training is measured by the joint kinematics. Due to tendon compliance, this method offers insufficient information about the muscle fiber behavior. The present study investigated the muscle fiber behavior of the Vastus Lateralis muscle (VL) during eccentric knee contractions in humans by measuring the changes of fascicle length in vivo with ultrasonography, at force levels of 65% and 95% of the maximum voluntary isometric contraction force (MVC). Seven young adults were tested by a Biodex. They performed eccentric knee contractions with one leg at 65% and 95% of their MVC (knee angle 25°-100°, angular velocity 90°/s). Potential joint axis deviations were recorded using a Vicon camera system. Exerted knee moments were captured synchronously with the Vicon system at 1000Hz. Fascicle length of the VL muscle visualized by a 10cm Ultrasound prob. The means and standard deviations of fascicle elongation at 65% and 95% of the MVC were 42.71±8.54mm and 39.11±10.64mm respectively, with no statistically significant difference between both conditions. All subjects showed a plateau or slide decrease in fascicle length at the beginning of the movement. This slight decrease in fascicle length, which occurs despite a lengthening of the VL muscle-tendon unite, can be explained by the tendon compliance. The similar fascicle elongation between the two conditions (65% vs. 95% MVC) reveals that the amplitude of the force level during eccentric knee extension contractions does not affect the lengthening of the fascicle.

Listed In: Biomechanics, Other

Direct Measurement of Sediment Response to Waves with Smart Sediment Grains

A comprehensive characterization of small-scale fluid-sediment interactions will improve understanding of large-scale ocean engineering phenomena, resulting in more accurate wave forecasting and improved ocean circulation models. The critical shear stress is typically used to determine the initiation of sediment motion in coastal applications. However, this shear stress criterion was primarily developed for steady flows and has been inconclusive in some wave environments where sediment motion may be induced by horizontal pressure gradients. Evidence suggests that the incipient motion formulation should account for the combined effects of the horizontal pressure gradients and bed shear stresses. Other researchers have made one-dimensional and two-dimensional measurements of near-bed velocities. However, previously available technologies could not resolve the three-dimensional velocities at the bed or directly measure sediment motion. Accurate investigation of the hydrodynamic forces that initiate coastal sediment transport requires high resolution measurements at the fluid-sediment interface. We have made previously unavailable high spatial and temporal resolution laboratory measurements at the sediment bed with state-of-the-art instruments. Additionally, we have performed one of the first direct measurements of sediment motion in response to waves with newly-developed electronic grains. The MEMs sensors are 2.5 x 1.5 x 1.4 cm and measure three-dimensional accelerations, store the data onboard, and transmit them wirelessly after retrieval. The Smart Sediment Grains (SSGs) were developed by embedding MEMs sensors in gravel-sized Delrin plastic spheres. These spheres allow uninhibited movement in any direction, similar to a smooth sand grain. The SSGs are the first freely moving electronic grains that measure sediment dynamics which previous technologies could not, giving insight into the underlying wave forces driving sediment transport. The SSGs enhance our ability to measure the motion, transport, and settling of sediments in the nearshore by capturing translation and rotation of the sediment. This will improve our predictive capabilities of sediment transport phenomena such as beach erosion and seabed evolution in response to wave forces; as well as improve parameterizations of the bottom friction for ocean circulation and wave energy dissipation models. The SSGs have been successfully deployed in small and field-scale wave flumes to measure the response of coarse gravel sediments to wave forcing. High resolution profiling Acoustic Doppler Velocimeters and a Particle Image Velocimetry system, comprising a laser and four high speed cameras, measured the three-dimensional fluid velocities at the bed. These measurements provide resolution high enough to fully examine the small-scale fluid forces exerted on each individual sediment grain. The SSGs accurately captured the sediment response to the waves at the onset of sediment transport. Additionally, broader incipient motion experiments were conducted with a variety of sediment grain diameters and densities for comparison. The results suggest evidence of pressure gradient influenced incipient motion; in contrast with the more commonly used threshold for sediment motion based on the bed shear stress. Calculated values of the Sleath parameter, used to quantify the effects of the pressure gradients, were comparable with field observations of pressure gradient induced sediment transport. The data also suggest that vortex shedding could be a factor in triggering sediment transport. We have directly measured incipient motion in waves by resolving the near-bed fluid velocities and collecting direct measurements of sediment motion with state-of-the-art instruments. The data are being used to validate theoretical and numerical models of the wave bottom boundary layer and bottom friction estimates. These results will be synthesized to propose a comprehensive incipient motion criterion comprising the effects of the shear stress and the pressure gradients, also taking into account a variety of flow and sediment characteristics. The current configuration of the SSGs helps to identify the characteristics of incipient motion and determine orientation. These mobile nodes make a significant step towards resolving the Lagrangian dynamics of individual coarse gravel-sized particles within the mobile bed layer in the nearshore. On a larger scale, they will reduce the effects of beach erosion by improving beach nourishment design. With technological advancements, these SSGs can be minimized and made field-deployable with enclosures configured to other applications to provide transformative measurements in geotechnical engineering, hydrology, oceanography and human health monitoring.
Listed In: Other