title: Toe spatiotemporal differences between transition steps when ascending shorter flight stairways of different heights.
abstract: BACKGROUND
  Studies have typically treated the first and second floor-to-stair transition steps (TS1 and TS2) as one stride. However, because the foot is devoid of plantar cutaneous input from the stair surface at TS1, these steps may have different toe spatiotemporal profiles, and resultantly, different susceptibilities to a trip and/or a fall. This study compared vertical toe clearance, forward velocity, and their respective variability magnitudes between TS1 and TS2 when ascending stairs of different heights.
  
  
  METHODS
  Twenty young adults (seven males and 13 females) (21.68 ± 2.49 years; 169.70 ± 9.56 cm; 63.91 ± 9.62 kg) negotiated an intervening three-step staircase placed midpoint on a 10 m walkway. There were three stair heights: low stairs (LS), medium stairs (MS), and high stairs (HS). Vertical toe clearance, forward velocity, and their variability magnitudes were calculated.
  
  
  RESULTS
  Vertical toe clearance was only higher (P < 0.05) at TS1 than TS2 in the medium and high stairs. Vertical toe clearance was more variable (P < 0.05) in the low compared to medium stairs. Also, forward toe velocity was greater at TS1 than TS2, but was lower in the medium and high stairs.
  
  
  CONCLUSIONS
  The locomotor system appeared cautious by exaggerating vertical toe clearance at both TS1 and TS2 only in low stairs, possibly due to higher forward toe velocity. If the exaggeration strategy consistently persists, this finding may suggest decreased trip or fall risk at both TS1 and TS2 only when transitioning onto low stairs.
authors.affiliation: Department of Kinesiology and Health, Georgia State University, Atlanta, GA, USA; Department of Kinesiology, Texas A&M University, Corpus Christi, TX, USA. Electronic address: toyin.ajisafe@tamucc.edu.
authors.forename: Toyin
authors.initials: T
authors.lastname: Ajisafe
authors.affiliation: Department of Kinesiology and Health, Georgia State University, Atlanta, GA, USA.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Kinesiology and Health, Georgia State University, Atlanta, GA, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Geil
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D008297:Male; D012449:Safety; D000072799:Stair Climbing / Q000502:physiology*; D014034:Toes / Q000502:physiology*; D055815:Young Adult
keywords: Fall risk; Floor-to-stair transition; Locomotor; Spatiotemporal variability; Stair ascent