Background: Treadmill walking should closely simulate overground walking for research validation and optimal skill transfer. Traditional fixed-speed treadmill (FS) walking may not simulate natural walking because of the fixed belt speed and lack of visual cues. Self-paced (SP) treadmill walking, especially feedback controlled SP treadmill walking, enables close-to-real-time belt speed changes with users' speed changes. Different sensitivity levels of SP treadmill feedback determine how fast the treadmill respond to user's speed change. Few studies have examined the differences between FS and SP treadmill walking, or the difference between sensitivity levels of SP treadmills, and their methods were questionable because of averaging kinematics and kinetics parameters, and failing to examine directly treadmill and subjects' speed data. This study compared FS with two SP modes with variation of treadmill speed and user's speed as dependent variables. Method: Thirteen young healthy subjects participated. Subjects walked on a motorized split-belt treadmill under FS, high sensitivity SP (SP-H) and low sensitivity SP (SP-L) conditions at normal walking speed. Root mean square error (RMSE) for subject's pelvis global speed (Vpg), pelvis speed with respect to treadmill speed (Vpt), and treadmill speed (Vtg) data were collected for all trials. Results: Significant condition effects were found between FS and the two SP modes in all RMSE values (p < 0.001). The two sensitivity levels of SP had similar speed patterns. Large subject × condition interaction effects were found for all variables (p < 0.001). Only small subject effects were found. Conclusions: The results of the study reveal different walking patterns between FS and SP. However, the two sensitivity levels failed to differ much. More habituation time may be needed for subjects to learn to optimally respond to the SP algorithm. Future work should include training subjects for more natural responses, applying a feed-forward algorithm, and testing the effect of optic flow on FS and SP speed variation. / text

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Background: When people walk while performing a cognitive dual-task, a decrease in gait velocity will occur because of the demand for some of the same cognitive resources. However, in a previous study they found an increase instead of a decrease in gait velocity when subjects walked on a self-paced treadmill while performing a color-word Stroop task. Aim: The aim of this study was to determine if the increase found in gait velocity in the previous study was a consequence of the subjects’ position. Additionally, it was investigated whether real-time feedback about the subjects’ position could substitute the lack of a reference point. Method: Position and gait velocity was measured in twelve healthy subjects during a trial consisting of eight control conditions and eight different interventions. Results: A significant difference was found in gait velocity between the interventions where the accelerations-line was moved furthest to the front and back (IzerolineA, IzerolineB) and in position between the original intervention and one with a neutral zone (Iorginal1, Ineutralzone). No differences were found in position or velocity with any of the feedback systems. Conclusion: From the results it could be concluded that the increase in gait velocity was a consequence of the subjects positioning themselves further in the forward direction on the treadmill. No conclusions could be drawn with the feedback systems.

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