The major outcome was to demonstrate that a robotic treadmill, theTreadport locomotion interface, significantly improves the gaits ofpatients with partial Spinal Cord Injuries (SCI) over standardtreadmill training in a clinic.  Patients walk more normally, fasterand longer, and more confidently.The features of the Treadport that differ from ordinary rehabilitationor exercise treadmills are (1) a large 6-by-10-foot belt, (2) anenveloping frontal visual display for projecting virtual realitysimulations of farms, cities, and even the Martian surface, and (3) amechanical tether that pushes and pulls on the user and that controlsmotion of the belt and motion of the use through a virtual world.Our first set of studies with 12 patients sought to understand whichfeatures of the Treadport were most responsible for the improvedresults.  Of the 3 features listed above, the key features wereself-selected speed by virtue of the operation of the mechanicaltether, and belt width.  The Treadport allows patients to set theirown speed of walking instantaneously, making it much more realisticthan clinical treadmills where speed is set by therapists.  The beltwidth allows patients to focus on walking through a virtualenvironment without worrying about stepping off the belt.  On a narrowbelt, patients kept their feet wider apart, apparently for stabilityreasons, but on the Treadport the patients kept a narrower distancesideways between feet, showing a greater sense of stability.Another set of studies with 12 patients looked at the longer-termeffect, where patients trained for 8 sessions over a 6-week period onthe Treadport and on the clinical treadmill each.  The results showedthat the rate of speed increase after 8 sessions was significantlygreater on the Treadport, meaning that the patients got better faster. The other major outcome was improvements to the hardware, control andsoftware to make the Treadport arguably the most realistic simulatorof real-world walking.  We highlight 3 such improvements.  (1)Previous research on ordinary treadmills indicated that stride lengthis shorter on treadmills than on the ground, but on the Treadport weshowed for the first time that walking on a treadmill can be the sameas on the ground.  The reason is that the mechanical tether pulls onthe user with prescribed forces to simulate missing inertial forces.The mechanical tether can also simulate slop walking without tiltingthe treadmill deck, which could lead to less expensive treadmills foreventual use in a clinic.(2) Another hardware addition was a 3-wire body weight support system,mounted in the ceiling.  The 3-wire system ensures that the supportforces are always vertical, which is important because of the large6-by-10 foot deck that allows the user to move around more than onordinary treadmills.  Body-weight support is required by somepatients.  It can help simulate reduced-gravity walking on Mars.  Itsuse was also shown to help simulate steep slope walking using themechanical tether force, since vertical forces are required to keepthe net forces on the body to equal the body weight.(3) An arm swing pacemaker was developed to assist SCI patients whoneed to relearn to swing their arms in rhythm with the step cycle.Arm swing is necessary to help stabilize the gait, and as aneurologically coupled motion to gait.  Although arm swing traininghas not yet been done on patients, studies were performed on healthysubjects to characterize what are normal arm-swing trajectories.  Totrigger the arm swing motions, a method was developed that convertsthigh-worn IMU signals into arm-swing trajectories.

Last Modified: 11/30/2017
Modified by: John M Hollerbach