METHODS AND MATERIALS
Motion analysis was performed using a computer-
aided video motion analysis system with five
infrared cameras (VICON) under the control of a
computer (DEC PDP 11/34). The results of threedimensional
accuracy and resolution (static and dynamic)
of the system showed that the system has a
composite accuracy of +3 mm and a resolution of
22 mm in each of the three coordinate directions
(9). Foot contact patterns were recorded using pressure-
sensitive foot switches (developed at Rancho
Los Amigos Hospital) attached to the heel, first and
fifth metatarsals, and great toe of each foot.
A group of 40 normal healthy subjects (age range
of 18-40 years, 28 males and 12 females) with no
previous history of musculoskeletal problems was
evaluated. The subjects were evaluated on three
different test days at least 1 week apart in order to
assess the repeatability of motion data (27). Prior to
recording the gait parameters, the height, weight,
lower limb length, knee width, and ankle width of
each subject were measured. After a brief orientation
session, the subjects were asked to walk at
their natural speed along the walkway to assess the
individual's free walking speed. Subsequent to the
practice session, four sets of gait data were collected
over a 3 m portion of the 9 m walkway. One
more set of data corresponding to the standing position
(static data) were also recorded, in order to
correct for any misalignment of the wand markers.
These procedures were repeated for each of the
lower limbs.