A dynamical systems investigation of lower extremity coordination during running over obstacles

Objective. To investigate intralimb coordination during running over a level surface and over obstacles of three different heights. Design. The phasing relationships between the foot and leg motions in the frontal plane, and the shank and thigh motions in the sagittal plane were used to compare patterns of coordination. Background. The coordinated actions of lower extremity segments are necessary to absorb the impact forces generated during running. The behavioral patterns of these segments can be studied under changing task demands using analysis techniques from the Dynamical Systems Theory. Methods. Ten subjects ran at their self-selected pace under four conditions: over a level surface and over obstacles of different heights (5%, 10%, 15% of their standing height). A force platform was used to record impact forces during landing after obstacle clearance, while kinematics were collected using a two-camera system. Results. The increases in obstacle height resulted in significant changes in impact forces (34% increase between the two extreme conditions) and more in-phase relationships between the segments during early stance. No changes were observed in the variability of the phasing relationships. Conclusions. The coordination changes observed might be compensatory strategies aimed to reduce forces and potential injury. However, since the impact forces still increased significantly, it is also possible that the observed changes might be at-risk movement patterns predisposing runners to injury.