Leading end assemblies for movable partitions may include at least one sensor assembly configured to detect a force applied to a leading surface of a leading structure of the leading end assembly. Movable partition systems may include a plurality of hingedly coupled panels and a leading end assembly. The leading end assembly may include a trolley movably coupled to a track and at least one sensor assembly configured to detect movement of the leading structure relative to the trolley when the movable partition is moved from a retracted position to an extended position. Methods of operating a movable partition may include monitoring a displacement of a leading structure of a leading end assembly of the movable partition relative to another portion of the leading end assembly with a sensor assembly and ceasing movement of the movable partition in response to a signal from the sensor assembly.