Articulators accelerate and decelerate continuously during speech. Previous research reveals a structured pattern of deceleration peaks aligning with segment onset and acceleration peaks with segment offset. This study reports on previous EMA findings on 18 speakers while also sets out to explain why the deceleration peak lags behind at onset boundary, as previously reported. A qualitative analysis is made on acceleration changes (jerk) of constrictions by one speaker. Preliminary results reveal significant differences between the kinematics of segment onset at constriction closure, which align to the jerk of the deceleration phase, and segment offset at the release, which coincide with the acceleration peak.