title: Self-selected gait speed--over ground versus self-paced treadmill walking, a solution for a paradox.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Young 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).
  
  
  RESULTS
  During 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).
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Center of Advanced Technologies in Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. meir.plotnik@sheba.health.gov.il.|Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel. meir.plotnik@sheba.health.gov.il.|Gonda Brain Research Center, Bar Ilan University, Ramat Gan, Israel. meir.plotnik@sheba.health.gov.il.
authors.forename: Meir
authors.initials: M
authors.lastname: Plotnik
authors.affiliation: Center of Advanced Technologies in Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. Tamar.Azrad@sheba.health.gov.il.
authors.forename: Tamar
authors.initials: T
authors.lastname: Azrad
authors.affiliation: Department of Neurological Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. Moshe.Bondi@sheba.health.gov.il.
authors.forename: Moshe
authors.initials: M
authors.lastname: Bondi
authors.affiliation: Center of Advanced Technologies in Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. yotam.bahat@gmail.com.
authors.forename: Yotam
authors.initials: Y
authors.lastname: Bahat
authors.affiliation: Center of Advanced Technologies in Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. yoavgimmon@gmail.com.|Department of Physiotherapy, Ben Gurion University of the Negev, Be'er Sheba, Israel. yoavgimmon@gmail.com.
authors.forename: Yoav
authors.initials: Y
authors.lastname: Gimmon
authors.affiliation: Department of Neurological Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. Gabi.Zeilig@sheba.health.gov.il.|Department of Physical and Rehabilitation Medicine, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel. Gabi.Zeilig@sheba.health.gov.il.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Zeilig
authors.affiliation: Department of Neurology, Sheba Medical Center, Tel Hashomer, Israel. rivka.inzelberg@gmail.com.|Department of Neurology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel. rivka.inzelberg@gmail.com.
authors.forename: Rivka
authors.initials: R
authors.lastname: Inzelberg
authors.affiliation: Department of Orthopedic Rehabilitation, Sheba Medical Center, Tel Hashomer, Israel. Itzhak.Siev-Ner@sheba.health.gov.il.
authors.forename: Itzhak
authors.initials: I
authors.lastname: Siev-Ner
mesh_terms: D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D014584:User-Computer Interface; D016138:Walking / Q000502:physiology*; D055815:Young Adult