Center of Mass Displacement in Young Adults While Experiencing External Disturbances During Sit-to- Stand Motion

Hannah N. Cohen*, Hannah D. Carey and Jessica L. Allen, Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26505

Field (Broad Category): Biomechanics/Kinesiology (Physical Sciences & Engineering) 

Student’s Major: Biomedical Engineering 

Many older adults have difficulty with the sit-to-stand motion, which is fundamental for daily life. Preventing a fall when a loss of balance occurs during sit-to-stand requires appropriate muscle recruitment. As a first step to understanding how fall prevention during sit-to-stand is altered in older adults, we investigated how healthy young adults recruit their muscles to control the movement of their center of mass (CoM) when experiencing an external disturbance during the sit-to-stand motion. Kinematic data was collected from subjects during the study using reflective ball markers. After performing the sit-to-stand motion as they would normally, subjects were exposed to external perturbations timed to occur after the subject began to stand. Perturbations were delivered through movement of the support surface 15cm forwards or backwards at different velocities in random order, each designed to produce varying levels of balance loss. OpenSim, an open-source musculoskeletal modeling software, was used to identify the contribution of lower-leg muscles to the return of the CoM towards a stable position across different perturbation directions and levels. Preliminary results indicate that peak anterior-posterior CoM displacement in response to the perturbation scales with increasing perturbation velocity. We expect to find that a) the recruitment of muscles used to return the CoM back to the stable position scales with perturbation velocity, and b) the muscles that contribute to this return depend on whether the perturbation was forward or backwards. 

Funding: West Virginia Research Challenge Fund 

Program/mechanism supporting research/creative efforts: WVU's SURE program