Comprehensive Understanding of Inactivity-Induced Gait Alteration in Rodents

The present protocol describes three-dimensional motion tracking/evaluation to depict gait motion alteration of rats after exposure to a simulated disuse environment.

Our protocol provides a comprehensive procedure to determine parameters for joint motion analysis. Joint motion analyses are often complicated due to lack of comprehensive definition of parameters. We show standard schematics of parameter definitions that are universally applicable to related fields.

To begin, open the MotionRecorder app. Place the rat on the treadmill belt. Increase the belt speed to 20 centimeters per second.

As the rat begins walking normally at the desired speed, click on the Record icon to start the video capture. Once 5 to 10 consecutive steps are obtained, stop the capture by clicking on the Record icon. Open the 3DCalculator app, and the video file to be analyzed.

Crop the video by adjusting the horizontal slider bar on the top, to contain enough numbers of consecutive steps. To capture the markers, drag the marker legends on the stick-picture model to the corresponding marker on the captured video, and release the button. Click on the Automatic Trace icon.

If the system does not accurately track markers, or the tracking process halts due to marker loss, switch to manual mode by clicking the Manual icon. Click the missing marker legend on the stick picture, and the corresponding marker on the video. Open the KineAnalyzer app and load the file.

Go to View, and click on Edit Marker Master menu. It will open the Marker master edit window. Click on the desired label or landmark on the marker"tab, then click on the desired color.

This process designates each marker to a specific landmark. Then on the link"tab, create lines that correspond to each limb by clicking on two markers consecutively. Assign colors to the created lines by selecting the desired color from the Color column.

Define angles on the angle"tab. After naming the angle, assign Vector A as the reference line, and Vector B as the moving line, by clicking on the markers corresponding to each landmark. Then define the direction of the angle with a value in the operate"section in the same tab.

Next, on the distance"tab, define the distance parameter. Select two corresponding markers in the Distance Setting section. Six animals each were randomly assigned to either the unloading group, in which the hind limbs of the animal were unloaded by the tail for two weeks, or the control group, in which the animals were left free.

The normalized joint trajectories for the knee and ankle during the stance phase showed that the unloaded group exhibited further extensions in the knee and ankle than the control group. Two weeks after unloading, quantitative measures such as knee angle at the mid-stance and ankle angle of the unloaded group were significantly greater than those of the control group. The metatarso-hip distance, which is virtually equivalent to the height of the hip joint at mid-stance, was also considerably higher in the unloaded group.

This method gave researchers the fundamentals of how to determine joint motion parameters. This way they can set up specific frameworks to address their own research questions.