When you play an animation of a biped character that travels, you can use In Place mode to keep the biped visible in the viewports. Use this for biped key editing, or adjusting envelopes with Physique. In Place mode prevents XY movement of the biped's center of mass during playback; motion along the Z-axis is preserved.
This control is a three-button flyout: you can also restrict X movement without restricting Y movement, or vice versa.
The state of In Place Mode is saved with the MAX file.
The In Place flyout is located on the expanded Biped rollout.