Currently, gait rehabilitation for gait deviations associated with stroke has focused on task-specific repetitive rehabilitation techniques. Body weight supported treadmill training has been used to administer this type of rehabilitation but is labor intensive for therapists. To alleviate the burden on therapists, mechanized or robotic gait trainers have been used to elicit gait-like movements. This study is focused on evaluating an elliptical trainer that was modified to provide an ankle articulation pattern similar to that found in normal gait. The kinematic, kinetic, and metabolic effect of the modifications on normal subjects was evaluated. Eight healthy adult subjects (4 male, 4 female; mean age 28.6 ± 5.2) participated in this research. Subjects were asked to ambulate on the elliptical trainer with and without the modifications at two metronome-paced speeds (1Hz and 1.5Hz). Video-based motion analysis techniques were used to collect sagittal plane kinematic data at a rate of 30 Hz. Reflective markers were placed over the acromion, greater trochanter, fibular head, lateral malleolus, heel, and fifth metatarsal. Metabolic Energy – The rate of energy consumption (VO2 consumption and VCO2 production) was measured using ventilatory expired gas analysis (SensorMedics, Yorba Linda, CA). The articulation of the footplate on the modified elliptical trainer correlated with the foot movement seen in normal ambulation (r2=0.89). It was found that for the ankle and knee, the joint angles while ambulating on the modified elliptical trainer correlated better to normal gait than the non-modified elliptical trainer. However, the hip angles were found to correlate worse. This suggests that the ankle articulation was successful, but the distal control was not as effective as expected. Kinetic energy was found to not be significantly different between the modified elliptical trainer and the non-modified elliptical trainer. Metabolic energy was found to be statistically higher on the modified elliptical trainer (p=0.001). This may suggests that there is co-contraction of muscles around joints. Further study using electromyography may provide further insight on the difference seen in metabolic energy consumption.

Elliptical trainers are prescribed in rehabilitative exercise but difficult to implement in populations with significant functional gait deficits. Typical elliptical machines do not mimic normal gait and therefore require modifications for clinical rehabilitation. This research builds on previous modifications of an elliptical trainer designed to simulate level-surface walking. This design differed from a commercial version. It included articulated footplates and an electromechanically-driven virtual-cam to control footplate position. Ankle dorsiflexion elicited lower-extremity muscle spasticity which produced an unwanted gait variant during stroke patient testing. Spasticity is a hyperexcitable stretch reflex causing inefficient gait. This project’s purpose was to develop an autonomous cam-profile adjustment to optimize the device’s rehabilitation potential. Foot-to-footplate forces were measured in stroke patients and compared to normative data. Greater than normal forces were considered spastic. An embedded controller was designed to reduce footplate forces via real-time cam-profile attenuation. A simulated spastic dorsiflexion load successfully proved the algorithm’s efficacy.