Gait adaptability, the ability to avoid obstacle and take visually guided steps are crucial for moving safely. Walking is an activity that requires the adjustment of gait according to the environment. For instance, the adjustment of gait is important when walking on an uneven terrain in order to find the right foot placement in relation to the features of the local environment. In addition, it determines the likelihood to fall since most falls are caused by a slip, trip or misplaced step. The assessment of gait adaptability in clinical practice is a difficult task.
Three groups of people were studied to assess the performance of their gait adaptability. They included a control group and two groups of participants with unilateral lower limb amputation and use prosthesis to walk. Lower limb amputations increase the likelihood and incidence of falls. Furthermore, people with lower limb amputations have reduced confidence in their balance and an increased fear of falling. To be able to regain their ability to walk safely, lower limb amputees require gait adaptability assessment to guide the interventions required.
A few studies have been performed to investigate how environmental constraints affect prosthetic gait adaptability. In the studies, the negotiation of obstacles was when walking on the ground or treadmill. The results indicated that lower limb amputees were more cautious than able bodied participants when avoiding obstacles. They also successfully avoided the obstacles without falling. When walking on the treadmill, however, those with transtibial amputation had a lower success rate in avoiding obstacles than the control group. From the results, it was concluded that lower limb amputees had an impaired online gait adjustment. However, their adjustment to earlier visible obstacles, i. e. two steps ahead, was done in an anticipatory manner. The findings also indicated that a treadmill with many obstacles would be valid in prosthetic gait adaptability assessment.
A study was done to determine how valid a treadmill based protocol was in the assessment of people with lower limb amputation. It was to test their online gait adjustment ability and anticipation to circumstances in the environment. A treadmill with visual obstacles and stepping targets was used in two conditions. In the first condition, the obstacles were presented one or four steps ahead. The evaluation of the gait adaptability was done in terms of how successful one reacted to or anticipated the obstacles. In the second condition, the treadmill had both regular and irregular patterns of stepping targets. The evaluation was done in terms of how accurate the visually guided steps were taken. The determination of face validity was achieved by examining if the gait adaptability scores varied among the three groups of participants, i. e. those with transfemoral amputations, transtibial amputations and able bodied participants. Walking depends on the level of amputation, therefore, it was expected that the group with transfemoral amputation record inferior scores, followed by the group with transtibial amputation and then able bodied participants with superior scores. The relationships between the scores of gait adaptability and other clinical tests were examined to determine the construct validity.
Each group of the participants comprised of 12 people. They were between 18 and 70 years old and had the ability to walk without any aid for a minimum of four minutes. Furthermore, they had no orthopedic, cardiorespiratory of neurological pathologies. A treadmill with force platform that allowed for the detection of gait events and characteristics was used. A projector was connected to the treadmill to show visual objects. With the exception of the control group, the other groups performed standard timed walking tests at comfortable and maximal walking speeds. All the participants walked on the treadmill for 5 minutes at various speeds.
The first condition consisted of two trials where each participant was confronted with 12 visual obstacles moving at the same speed as the belt speed. During the trial of anticipatory obstacle avoidance, an obstacle was presented at foot contact, four steps before the anticipated contact. This allowed for adjustment to avoid the obstacle. In the trial for reactive obstacle avoidance, an obstacle was presented under time pressure, one step before contact anticipation. This allowed for adjustment during swing phase to avoid obstacle.
The second condition was examined using rectangular stepping targets. These were projected on the treadmill for both feet. The participants had to walk on the step pattern present aligning their feet appropriately. The condition had three trials with stepping patterns of varying regularities. The stepping accuracy was determined in millimeters and quantified in terms of the foot placement relative to the stepping targets.
All the participants successfully finished conditions one and two. Participants in the transfemoral group walked more slowly on the treadmill compared to both the transtibial and the able bodied groups. The rates of success for the anticipatory obstacle avoidance were higher than the reactive obstacle avoidance for the three groups.
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Houdijk, Han, et al. Assessing Gait Adaptability in People with Unilateral Amputation on an Instrumented Treadmill with a Projected Visual Context. New York: American Physical Therapy Association, 2012.