The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Do kinematics signal energetic optimality? Evidence from human walking studies


Biology, Seattle Pacific University

March 27, 2015 , Archview Ballroom Add to calendar

Previous research has indicated that humans have an “optimal” speed (a speed at which cost of transportation is lowest), and that people preferentially choose to walk around this speed; however, it is unknown how people gain the real time feedback necessary to determine optimality. Gait kinematics have been indicated as a potential feedback mechanism and here we evaluate energy and kinematics on humans walking at multiple inclines.

Participants (n=5) were evaluated in two trials in which they walked at four different speeds on both a level and 12% incline, while their energy consumption was monitored; participants identified preferred speeds for each grade at the end of each trial. Posterior video data were analyzed to determine step width and contact time using Kinovea software. Stride length was calculated from stride frequency measured during each speed.

People were better able to detect their optimum speed at the incline. Stride length increased linearly with speed nearly identically (slopes 4.5% different) for both the level (R²=0.93) and inclined (R²=0.90) conditions. Contact time decreased linearly nearly identically (slopes 10.8% different) for both the level (R²=0.96) and inclined (R²=0.90) conditions. Neither stride length nor contact time showed curvature or other cues as to identifiable optimality. Step width showed a wide variation between and within each participant, with a greater coefficient of variation for the incline condition (21.5% increase) and for speeds away from the optimum (34% at the incline). It is thus possible that increased variation gives an indication of energetic cost while walking.