Development of an Elliptical Perturbation System that provides unexpected perturbations during elliptical walking (the EPES system)

Abstract

Background: 'Perturbation-based balance training' (PBBT) is a training method that was developed to improve balance reactive responses to unexpected balance loss. This training method is more effective in reducing fall rates than traditional balance training methods. Many PBBTs are performed during standing or treadmill walking which targeted specifically step reactive responses, we however, aimed to develop and build a mechatronic system that can provide unexpected perturbation during elliptical walking the Elliptical Perturbation System (the EPES system), with the aim of improving specifically the trunk and upper limbs balance reactive control.

Methods: This paper describes the development, and building of the EPES system, using a stationary Elliptical Exercise device, which allows training of trunk and upper limbs balance reactive responses in older adults.

Results: The EPES system provides 3-dimensional small, controlled, and unpredictable sudden perturbations during stationary elliptical walking. We developed software that can identify a trainee's trunk and arms reactive balance responses using a stereo camera. After identifying an effective trunk and arms reactive balance response, the software controls the EPES system motors to return the system to its horizontal baseline position after the perturbation. The system thus provides closed-loop feedback for a person's counterbalancing trunk and arm responses, helping to implement implicit motor learning for the trainee. The pilot results show that the EPES software can successfully identify balance reactive responses among participants who are exposed to a sudden unexpected perturbation during elliptical walking on the EPES system.

Conclusions: EPES trigger reactive balance responses involving counter-rotation action of body segments and simultaneously evoke arms, and trunk reactive response, thus reactive training effects should be expected.

Keywords: Balance reactive responses; Falls; Old people; Perturbation-based balance training.

Fig. 1

The final system. a Illustration of how the subject is connected to the safety harness system, b presentation of the system components

Fig. 2

The motion platform system. a Front view, b top view

Fig. 3

a The EPES software’s ability to monitor and identify the process of the participant’s sensorimotor adaptation to hands-fee pedaling (when the trainee connecting to the stationery secure system), b illustration of the defined angles (see text for further descriptions of joint angels)

Fig. 4

A section from the CSV file was opened using Excel software that includes the time and the different angles (α1–α7 in degree)

Fig. 5

The EPES communication flow chart

Fig. 6

Calibration time and checking the user’s response during left perturbation flow charts

Fig. 7.

8° right tilt perturbation. a Camera image during the experiment, b a graph created from the saved CSV file. The system roll angle increases by 8° (dark line, α6), followed by a large balance recovery reaction as seen by the 12° trunk angle (orange line, α2) and about 14° shoulder angle (light blue line, α1) is, as clearly seen in B. Immediately after an effective balance recovery response was detected by the software, the EPES system returns to its initial horizontal condition (dark line, α6)

Fig. 8.

8° left tilt perturbation. a Camera image during the experiment, b a graph created from the saved CSV file. The system roll angle increases by 8° (dark line, α6), followed by a large balance recovery reaction as seen by about 17° right trunk angle (orange line, α2) and about 20° right shoulder angle (light blue line, α1) is, as clearly seen in b. Immediately after a good balance recovery response was detected by the software, the EPES system returns to its initial horizontal condition (dark line, α6)

Fig. 9

Example of an experiment: a camera image during the experiment, b a graph created from the saved CSV file. The system’s angle (α6) increases by 3° left tilt perturbation (A); 5° left tilt perturbation (B); and 8° left tilt perturbation (C). All perturbations are followed by a balance recovery reaction (angle α1 and α2) that was detected by the software, the EPES system returns to its initial horizontal condition as clearly seen (α6). There is a clear gradation in the participant balance recovery response based on the size of the disturbance