1Anthropology, University of Washington, 2Department of Orthopaedics and Sports Medicine, University of Washington
March 27, 2015 , Archview Ballroom
Describing the gait cycle, including parameters like heel strike (HS) and toe-off (TO), is key to understanding the kinematic patterns of moving primates, because kinematics can often reveal important characteristics of an animal’s interaction with the environment. For instance, contact time, the time in contact with the substrate, has been correlated with the energy expenditure of locomotion. A laboratory setting with automatically detected markers and multiple force plates that unequivocally establish when contact occurs is ideal, but not always feasible. Evaluating locomotion in natural environments rarely can rely on force plates, so HS and TO is predicted from some criteria, such as the velocity of particular landmarks. In humans, instantaneous velocity of the heel and the metatarsal-phalangeal joints are frequently used.
To establish the efficacy of the instantaneous velocity criteria, we collected the kinematic data of 20 females using an eight-camera Qualisys motion capture system with a Kistler force plate. Participants walked shod and unshod (30 trials each) at self-selected slow, medium, and fast velocities. We used marker data to predict HS and TO and compared these predicted values to the HS and TO values assessed using the force plate. We found that the prediction is strongly influenced by the progression velocity (p < 0.001, r2=0.84). In light of these findings, we are developing a more complex algorithm to identify reliably HS and TO in the absence of a force plate.