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.
Mechanosensitive cells, such as osteocytes in bone, are capable of translating mechanical stimuli into cellular responses. This phenomenon can be widely found in cells throughout the body, and yet little is known about the mechanisms and pathways by which this occurs. Research in this field has focused on creating in vitro models that better reflect the in vivo environment in order to study these mechanisms and pathways. Where many variations on these systems exists, one major goal in improving these models is to use fewer cells in order to observe the response of specific cells and possibly more meaningful data. Using an uniaxial loading device, a substrate with cells seeded onto it can be mechanically strained and the response of these fewer cells can be quantified. In this study, two substrates of varying geometry are proposed that allow for a gradient of mechanical strains to be applied to cultured cells. These designs are characterized and compared using both physical and simulated testing. Utilizing designs, such as the ones used for these substrates, enables the effects of a wide range of mechanical strains on cells to be observed and studied under identical culture and loading environments
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.
2013-2014 $10,000 Academic Scholarship Awardees
The Force and Motion Foundation's $10,000 Academic Scholarship is awarded annually to promising graduate students in fields related to multi-axis force measurement and testing. The 2013-2014 year's subject focus was: biomechanics research using multi-axis force measurement or multi-axis orthopaedic joint testing.
After considering many well-written applications, the Force and Motion Foundation is pleased to announce the three awardees of the 2013-2014 $10,000 Academic Scholarship.