One of the most powerful features of footsteps is the ability to adapt keyframes automatically to edits you make to your footstep pattern. By analogy, the footsteps become a kind of gizmo for manipulating the keyframes of your character's animation. In most cases, edits you make to footsteps act upon your keys in an intuitive fashion.
In order to understand what happens when active footsteps are edited, you must first understand what happens to biped keys when footsteps are activated. See Understanding Footstep and Body Keys.
When you move or rotate active footsteps as described in Editing Footstep Placement, the biped's keys are immediately influenced by the edit. The following keyframe tracks are influenced in the vicinity of the edited footsteps:
Other keys are preserved in the adaptation process. For example, if you animate the body to kneel while turned to the right, altering a nearby footstep will maintain the biped's height and turning motion as much as possible.
To edit active footsteps in time, follow the methods described in Editing Footstep Timing. Keyframes affected by the edit are updated immediately.
A fundamental factor in how your keyframes are adapted is whether the sequence of leg support transitions has changed. Changing the relationship between opposite leg keys effectively changes the gait, which causes entirely new keyframes to be generated at that point.
You can lock specified tracks to prevent them from adapting automatically when you move active footsteps. The controls in the Footstep Adapt Locks group on the Dynamics & Adaptation rollout lock specified tracks.
To prevent keys from changing when active footsteps are edited:
The tracks you lock are unaffected by footstep editing.