Meeting Abstract

103.1  Thursday, Jan. 7  How do humans stabilize running? QIAO, Mu; JINDRICH, Devin L*; Arizona State University; Arizona State University devin.jindrich@asu.edu

The control strategies used to stabilize running are not well understood. However legged robots are capable of stable running based on three simple control rules: maintain running speed, height, and pitch angle. We tested whether humans use the same rules. Specifically: 1) humans control running height by modulating leg force (not stance duration), 2) humans control running speed by changing stance leg placement relative to a “neutral point”, and 3) whether humans control body attitude using hip torques. We used a VICON® 3-D motion tracking system, and two force platforms (Bertec) covered by rubber mats to obscure the force platforms. 19 male participants (age = 27.2 ± 4.2years; body weight = 70.8 ± 8.3kg; body height = 178.9 ± 7.3cm) performed 6 trials in each of five running tasks: constant velocity running, acceleration, deceleration, stepping up and stepping down. All procedures were approved by the Institutional Review Board in Arizona State University. Leg force scaled by weight was linearly related to running height scaled by body height during up stepping tasks (R^2 = 0.63). In contrast, loading time was not correlated with running height (P = 0.003). Running speed was controlled by adjusting foothold placement relative to a neutral point (NP), which equals one half of the product of touch down velocity and subsequent stance duration. There was a significant linear relationship between center of pressure (COP)-to-NP displacement and velocity increment (R^2 = 0.78; P < 0.05). Finally, joint hip moments was linearly related to body pitch angle and its corresponding time derivative (R^2 = 0.79±0.20; P < 0.05). Although humans are morphologically more complex than robots, the simple control laws successful for robot stability could potentially also be employed by humans.