387. HIGH-SPEED TREADMILL RUNNING IN YOUNG AND OLD MICE RECORDED WITH MARKER-BASED 3D MOTION CAPTURE

Abstract Background In our previous studies, we adapted a marker-based 3D motion capture system to evaluate fine step kinematics during behaviors such as climbing and novel environment exploration under various pharmacological treatments in mice. Aims & Objectives In the present study, we aimed to test whether the step kinematics of mice is affected during treadmill running at different speeds in mice at young and old age. Method We used adult male C57BL/6 mice at the age of 3 and 18 months in a within-subject design. We recorded voluntary running behavior on a treadmill in mice implanted with permanent markers located at strategic locations: hips, lumbar spine, shoulder blades, hindlimb knees, and ankles. A high-speed, high-resolution 3D motion capture system (Qualisys, Sweden) was used to track movement (3D trajectories and velocity of markers) during voluntary running. Every mouse was recorded for 30 s running at speeds ranging from 10 m/min to 40 m/min, doubled with each trial until failure. Results Mean and maximum speed of ankle swing significantly increased with the increasing speed of running on the treadmill and the direct distance of the swing also increased while the duration of the swing significantly decreased. We did not observe any significant effects on swing height in young mice. These observations are in contrast to our previous results where we did not observe any effects on swing duration during climbing or open field exploration, but we did observe effects on swing height. Interestingly, when we tested the same mice at the age of 18 months, their maximum running speed did not decrease and was even slightly faster than at young age. The increases in swing speeds and direct distance as well as decrease in step duration with the increase of running speed were significantly more pronounced than at a young age. Moreover, In aged mice we observed significant asymmetry between left and right leg in swing height, where left leg was making higher ankle swings on average. This suggests that aged mice develop asymmetry in swing height with age. Discussion & Conclusions The present results indicate that kinematics during high-speed treadmill running can be assessed in mice over 18 months old without a decrease in performance. In conclusion, our results suggest that marker-based 3D motion capture is an accurate and precise method to quantify high-speed fine kinematics in young and old mice.