BackgroundThe study of gait at self-selected speed is important. Traditional gait laboratories being relatively limited in space provide insufficient path length, while treadmill (TM) walking compromises natural gait by imposing speed variables. Self-paced (SP) walking can be realized on TM using feedback-controlled belt speed. We compared over ground walking vs. SP TM in two self-selected gait speed experiments: without visual flow, and while subjects were immersed in a virtual reality (VR) environment inducing natural visual flow.MethodsYoung healthy subjects walked 96 meters at self-selected comfortable speed, first over ground and then on the SP TM without (n=15), and with VR visual flow (n=11). Gait speed was compared across conditions for four 10 m long segments (7.5 – 17.5, 30.5 – 40.5, 55.5 – 65.5 and 78.5-88.5 m).ResultsDuring over ground walking mean (± SD) gait speed was equal for both experimental groups (1.50 ± 0.13 m/s). Without visual flow, gait speed over SP TM was smaller in the first and second epochs as compared to over ground (first: 1.15 ±0.18 vs. second: 1.53 ± 0.13 m/s; p<0.05), and was comparable in the third and fourth (1.45 ± 0.19 vs. 1.49 ± 0.15 m/s; p>0.3). With visual flow, gait speed became comparable to that of over ground performance already in the first epoch (1.43 ± 0.22 m/s; p>0.17). Curve fitting analyses estimated that steady state velocity in SP TM walking is reached after shorter distanced passed with visual flow (24.6 ± 14.7 m) versus without (36.5 ± 18.7 m, not statistically significant; p=0.097). Steady state velocity was estimated to be higher in the presence of visual flow (1.61 ± 0.17 m/s) versus its absence (1.42 ± 1.19 m/s; p<0.05).ConclusionsThe SP TM walking is a reliable method for recording typical self-selected gait speed, provided that sufficient distance is first passed for reaching steady state. Seemingly, in the presence of VR visual flow, steady state of gait speed is reached faster. We propose that the gait research community joins forces to standardize the use of SP TMs, e.g., by unifying protocols or gathering normative data.

Objective: To analyze if and how arm movement manipulations affect lower inter-limb coordination and symmetry during self-paced treadmill walking. Design: Observational. Setting: Self-paced treadmill. Participants: Sixteen healthy men and women, aged 18-40 (8 women; 33.2 AE 4.5 y; BMI: 22.6 AE 3.7; 8 men; 32.4AE 6.5 y; BMI: 25.2 AE 1.9); eight with left motor and eight with right motor dominancy. Interventions: Participants performed walking trials on a self-paced treadmill. In each trial unilateral or bilateral arm swinging manipulations were performed by applying external verbal cues or forces (e.g., weights on one/both wrists). Main Outcome Measures: 1. Phase Coordination Index (PCI) quantifies the consistency and accuracy of the anti-phase stepping pattern and assesses the bilateral coordination of gait (BCG). Higher PCI values represent worse coordination. 2. Gait asymmetry (GA) is quantified based on the differences between right and left legs swing times. Results or Clinical Course: Most arm swinging manipulations resulted in a decrease of BCG but didn't influence GA. Walking with exaggerated both arms swinging resulted in higher PCI values (4.46 AE 1.35 % vs. 3.47 AE 0.96 % at baseline, P¼.01). There was a gender difference in baseline PCI values (Male PCI ¼ 3.86 AE 1.18%, Female PCI ¼ 3.08 AE 0.62%, P¼.05) and in a similar trend, male's PCI were aggravated to a greater extent than female's PCI in response to arm swinging manipulations. Regardless the side of motor dominancy unilateral manipulation of arm swinging affected significantly (P<.05) the swing amplitude of the contralateral arm. Conclusion: The results of this study confirm that arm swinging influences the motor coordination between the lower limbs during walking. Incorporating personalized upper limb movement interventions may contribute to improve gait performance in asymmetrically neurological impaired population during gait rehabilitation.