About Default Constraint Behavior
When the manikin_drag_auto_locks configuration option is set to yes, default placement constraints are applied to a manikin.
Depending on the context, when the Manikin tab is open, the following fix constraints appear in the Manikin Tree under 
Manikin Constraints:
Manikin Constraints:• Left Forefoot manikin segment is fixed
• Right Forefoot manikin segment is fixed
• Pelvis (Sacrum) manikin segment is fixed, and the other manikin segments in the Trunk manikin segment group are locked.
◦ When the manikin is a sub-assembly under a top-level assembly, the Pelvis appears in the Manikin Constraints folder.
Manikin Constraints folder.◦ When the manikin is open as a top-level assembly in a separate window, the Pelvis manikin segment does not appear in the Manikin Constraints folder.
Manikin Constraints folder.When you insert a manikin into an assembly, two placement connections are automatically added to the manikin structure, one for the right forefoot, and one for the sacrum (hips). To view the default connections in the assembly when the Model tab is open, right-click the manikin placeholder and selectEdit Definition from the shortcut menu.
When you place the manikin and select the posture, one of the placement connections is activated, the right forefoot connection if you select Standing, and the sacrum connection if you select Sitting. When you select the Place on reference, a placement constraint is created between the reference and the right forefoot of a standing manikin, or the sacrum of a sitting manikin.
The placement connections define the manikin’s initial position and orientation in the model. As a result, some manikin motion might be limited. For example, the manikin’s right forefoot is connected to the placement plane and cannot be lifted. You can disable the connections temporarily by right-clicking the manikin node of the Manikin Tree and selecting 
Disable Placement Connections. You can enable the placement connections later by selecting Enable Placement Connections.
Disable Placement Connections. You can enable the placement connections later by selecting Enable Placement Connections.A manikin's trunk is constrained so that it is always rigid, making manipulation easier. To move the spine, you must select a spine segment from the Manikin Tree and unlock the spine. You can then add more specific constraints such as locking specific vertebrae to prevent rotation (the DOF Z constraint).
A manikin's hips and toes are locked. If you select a leg, the toes lock into place on the ground. You can then change the location of the foot by dragging the manikin's toes by themselves. Toe and hip constraints are temporarily turned off when they are dragged.
When you select another segment to drag, the default constraints on the first segment are turned back on. If you drag the hips up and down, the toes remain on the ground. To manipulate the manikin into a squatting position, drag the hips.
 | To disable the placement constraints completely, right-click and select Disable all constraints from the shortcut menu. |
Video
See working with the foot constraints in a video.