Thanks to the observations of a user, we have discovered that a warning message displayed when loading data to the KINARM_add_Jerk.m function is incorrect.  The warning message indicates that unfiltered data must be used when applying this function.  Our user discovered a variance between different Kinarm systems which could be explained by whether the Kinarm Lab had a (older) PMAC  or (new) EtherCAT based control card.  We have now determined that data must be filtered with a 10 Hz filter before using the Jerk function not after as indicated by our warning message.

Who is impacted: users with a PN 10288 (Kinarm End-Point Lab w PMAC) or PN 10755 (Kinarm Classic w PMAC) could experience significant differences between pre-filtered jerk analysis and post-filtered jerk analysis. Why: PMAC systems collect position data at 1.13 kHz and then re-sampled, which introduces noise.

The fix:  only load data that has been filtered with a 10 Hz filter into the KINARM_add_Jerk.m function.

The correction:  The filtering needs to be applied BEFORE calculating jerk, in order to avoid possible edge effects at the beginning (or end) of a trial. The warning and documentation will be updated in a future release.

Please contact us at if you have any concerns about the impact of this change.  Your feedback will be used to help us determine the urgency of releasing a new version of KAS.