preferred_name: Able to independently walk on even and uneven surfaces and negotiate stairs with or without railings (specifically: needs no human assistance or assistive device).
preferred_name_lc: able to independently walk on even and uneven surfaces and negotiate stairs with or without railings (specifically: needs no human assistance or assistive device).
label: Able to independently walk on even and uneven surfaces and negotiate stairs with or without railings (specifically: needs no human assistance or assistive device).
label_lc: able to independently walk on even and uneven surfaces and negotiate stairs with or without railings (specifically: needs no human assistance or assistive device).