Incorrect position calculation from IMU for gait analysis

Hello All, i am trying to do gait analysis using an IMU. I am using a zero velocity update algorthm to force the food valeocity to zero when it is stationary. The final position i am calcualting is less than what i am expecting, and there is a change in position in axis where there should not be. Does anyone have any ideas as to why this my be the case? Ive attached a picture after of the position plot after i walked 8 meters with an IMU strapped to my foot.

The IMU i am using also outputs quaternions (if that is helpful?)

Thank you for any help

[James Tursa]

You will need to show us the algorithm/code you are using. Yes, you need to use the quaternion data to orient the acceleration values in order to get proper displacement calculations.