title: A markerless system based on smartphones and webcam for the measure of step length, width and duration on treadmill.
abstract: OBJECTIVE
  A markerless low cost prototype has been developed for the determination of some spatio-temporal parameters of human gait: step-length, step-width and cadence have been considered. Only a smartphone and a high-definition webcam have been used.
  
  
  METHODS
  The signals obtained by the accelerometer embedded in the smartphone are used to recognize the heel strike events, while the feet positions are calculated through image processing of the webcam stream. Step length and width are computed during gait trials on a treadmill at various speeds (3, 4 and 5 km/h).
  
  
  RESULTS
  Six subjects have been tested for a total of 504 steps. Results were compared with those obtained by a stereo-photogrammetric system (Elite, BTS Engineering). The maximum average errors were 3.7 cm (5.36%) for the right step length and 1.63 cm (15.16%) for the right step width at 5 km/h. The maximum average error for step duration was 0.02 s (1.69%) at 5 km/h for the right steps.
  
  
  CONCLUSIONS
  The system is characterized by a very high level of automation that allows its use by non-expert users in non-structured environments. A low cost system able to automatically provide a reliable and repeatable evaluation of some gait events and parameters during treadmill walking, is relevant also from a clinical point of view because it allows the analysis of hundreds of steps and consequently an analysis of their variability.
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy. Electronic address: v.barone@univpm.it.
authors.forename: V
authors.initials: V
authors.lastname: Barone
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy. Electronic address: f.verdini@univpm.it.
authors.forename: F
authors.initials: F
authors.lastname: Verdini
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy. Electronic address: l.burattini@univpm.it.
authors.forename: L
authors.initials: L
authors.lastname: Burattini
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy. Electronic address: f.dinardo@univpm.it.
authors.forename: F
authors.initials: F
authors.lastname: Di Nardo
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, Ancona, Italy. Electronic address: s.fioretti@univpm.it.
authors.forename: S
authors.initials: S
authors.lastname: Fioretti
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D000068997:Smartphone; D016138:Walking; D055815:Young Adult
keywords: Homographic transformation; Markerless system; Stride length; Stride width; Triaxial accelerometer