4th Annual WML Academic Symposium

Pathology has been associated with changes in the variability of joint kinematics and gait parameters such as cadence, step width and step length. However, little is known about the variability of motion of the center of mass with changes in mechanical demand. The purpose of this study was to examine the relationship between regularity of motion at the center of mass (L5S1) and the trunk with increasing mechanical demand. METHODS: Nine healthy young adults (22.8±3.5 yrs, 1.74±0.13 m, 70.0±18.2 kg) performed two 30-second treadmill walking trials at three treadmill velocities including their preferred walking velocity as well as 80% (SLOW) and 120% (FAST) of their preferred velocity. An 8-camera motion capture system (240Hz) was used to track the trajectory of retro-reflective markers placed on the posterior aspect of the trunk and the L5S1 joint. Custom software (MatLab 2009) was used to re-sample the data at 24 Hz and calculate approximate entropy values for the mediolateral marker trajectories using previously published equations. SPSS was used to conduct correlation analyses to determine the relationship between regularity of L5S1 and trunk motions. RESULTS: Results indicated strong, significant correlations between the regularity of L5S1 and trunk motion in the preferred (r=0.767, p=0.027), SLOW (r=0.754, p=0.019) and FAST conditions (r=0.713, p=0.047). DISCUSSION: These data show that variability of L5S1 and trunk motion is strongly related and that researchers interested in assessing variability of center of mass motion may place sensors either at the level of the pelvis (L5S1) or trunk.