Effect of direction of motion on joint and body kinematics curves

[Sharmita Dey]

I have biomechanical data from two trials (ascent and descent) recorded while subject was moving in opposite directions. Since, I am interested in the ankle angle and shank angular velocity of the two trials, I run the IK and Analysis tool and plotted the resultant curves (see attached). I am a bit confused if I need to flip the curves for on of the trials for a valid comparison between the two trials. If so, do I need to flip the curves for both joint angles and body kinematics? I compared my ankle angle curves (without flipping any) with (Riener, 2002) and found that they look similar. However, the shank angular velocity curves (for which I could not find any literature for comparison) for the two trials seems to follow different signs and this may be due to the effect of movement direction. I am not able to figure this out. Could you please advice me on this?

References:
Riener, Robert, Marco Rabuffetti, and Carlo Frigo. "Stair ascent and descent at different inclinations." Gait & posture 15.1 (2002): 32-44.

[Thomas Uchida]

Sign conventions may differ between models. You can simply open the model in the GUI, load your IK results, and look at the motion of the joints and body segments to be sure you are correctly interpreting the directions.

[Sharmita Dey]

Hello,

Thank you!