Altered gait biomechanics associated with pediatric obesity may increase the risk of musculoskeletal injury/pathology during physical activity and/or diminish a child’s ability to engage in sufficient physical activity. The biomechanical mechanisms responsible for the altered gait in obese children are not well understood, particularly as they relate to increases in adipose tissue. The purpose of this study was to investigate the role of adiposity (i.e. body fat percentage, BF%) on lower extremity kinematics, muscle force requirements and their individual contributions to the acceleration of the center of mass (COM) during walking. We scaled a musculoskeletal model to the anthropometrics of each participant (n=14, 8-12 years old, BF%: 16-41%) and generated dynamic simulations of walking to predict muscle forces and their contributions to the acceleration of the COM. Muscle force output was normalized to muscle mass. BF% was correlated with average knee flexion angle during stance (r=−0.54) and pelvic obliquity range of motion (r=0.78), as well as with relative vasti (r=−0.60), gluteus medius (r=0.65) and soleus (r=0.59) force production. Contributions to COM acceleration from the vasti were negatively correlated to BF% (vertical: r=−0.75, posterior: r=−0.68, respectively), but there was no correlation between BF% and COM accelerations produced by the gluteus medius. The functional demands and relative force requirements of the hip abductors during walking in pediatric obesity may contribute to altered gait kinematics. Our results provide insight into the muscle force requirements during walking in pediatric obesity that may be used to improve the quality/quantity of locomotor activity in this population.
Mechanotransduction studies aim to understand the process of cells converting mechanical stimuli into a cellular response. As it can be difficult to study the impact of isolated factors using in vivo studies, in vitro studies may offer more precisely controlled loads for experiments and allow cell culture on a variety of surfaces. Here, we developed a microloading platform for in vitro mechanotransduction studies, stretching the substrate by tenting it with a centrally contacting platen. This platform works through the use of a load cell and microactuator, which was characterized by comparing the reported and measured displacements. In addition, an alignment block was designed for the microloading platform to improve reproducibility between studies, and a cell culture handling system was designed to hold samples before experimentation and reduce preloads, allowing the study of only the controlled loading. A polydimethylsiloxane (PDMS) scaffold was also designed for cell loading, complete with a positional reference grid for observing the response of individual cells to strain. Initial work with this microloading platform includes studying osteocyte like MLO-Y4 cells, and changes in viability in response to mechanical load in vitro. These initial studies have demonstrated the ability to induce cell death in response to mechanical load.
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.
2014-2015 $10,000 Academic Scholarship Season Opens Monday!
The Force and Motion Foundation is pleased to announce the opening of our annual scholarship competition. Three $10,000 scholarship awards have been set aside for promising research involving multi-axis measurement or multi-axis testing. Two awards will be designated for graduate students at U.S. universities, while a third award is open to students internationally.
These $10,000 Academic Scholarships are awarded annually to promising graduate students in fields related to multi-axis force measurement and testing. The 2014-2015 cycle's subject focus is: Biomechanics Research Using Multi-Axis Force Measurement or Multi-Axis Orthopaedic Joint Testing.
2014-2015 $10,000 Academic Scholarship