Clarification of the 'flip' parameter of 'GaitPy'

[ezeid]

Hi,

It is mentioned: Baseline vertical acceleration data is -9.8m/s^2 or -1g. If your baseline data is +9.8m/s^2 or +1g, set the ‘flip’ argument to True.

What is meant here. Do you mean if at baseline (e.g. while standing still and not moving) if the vertical acceleration reads +1g or any positive value the flip argument should be set to True?

How does the flip parameter affect the results? Does it flip the minima and the maxima (i.e. IC will appear at a maximum acceleration instead of minimum acceleration)?

Thank you
ezeid

[matt002]

Hey @ezeid, Yes exactly - just as you put it, at baseline (while standing) the vertical acceleration should read approximately -1g. If it reads +1g you may set the flip argument to True. In the most recent version of GaitPy1.6.1 if signal is at +1g and the flip parameter is not set to True it will flip the data for you before processing and print a warning. One of the reasons for this functionality is, like you mention, to make sure the peak detection is detecting minima and maxima correctly. Another reason is to provide information related to the orientation of the device on the patient to verify the degree to which the patient is wearing the device correctly. This becomes more important in at-home use cases where the patient may be assigned to put the device on themselves.

[ezeid]

Thank you Matt for your prompt reply. I am wondering whether you have tested or know how the GaitPy behave (is valid) on wrist worn accelerometer instead of back?

[matt002]

Happy to help. GaitPy has not been validated on a wrist worn device. It likely would not produce accurate measures from the wrist location without substantial tweaks.