First in vivo assessment of “Outwalk”: a novel protocol for clinical gait analysis based on inertial and magnetic sensors

  • Alberto Ferrari
  • Andrea Giovanni Cutti
  • Pietro Garofalo
  • Michele Raggi
  • Monique Heijboer
  • Angelo Cappello
  • Angelo Davalli
Original Article


A protocol named “Outwalk” was recently proposed to measure the thorax–pelvis and lower-limb kinematics during gait in free-living conditions, by means of an inertial and magnetic measurement system (IMMS). The aim of this study was to validate Outwalk on four healthy subjects when it is used in combination with a specific IMMS (Xsens Technologies, NL), against a reference protocol (CAST) and measurement system (optoelectronic system; Vicon, Oxford Metrics Group, UK). For this purpose, we developed an original approach based on three tests, which allowed to separately investigate: (1) the consequences on joint kinematics of the differences between protocols (Outwalk vs. CAST), (2) the accuracy of the hardware (Xsens vs. Vicon), and (3) the summation of protocols’ differences and hardware accuracy (Outwalk + Xsens vs. CAST + Vicon). In order to assess joint-angles similarity, the coefficient of multiple correlation (CMC) was used. For test 3, the CMC showed that Outwalk + Xsens and CAST + Vicon kinematics can be interchanged, offset included, for hip, knee and ankle flexion–extension, and hip ab-adduction (CMC > 0.88). The other joint-angles can be interchanged offset excluded (CMC > 0.85). Tests 1 and 2 also showed that differences in offset between joint-angles were predominantly induced by differences in the protocols; differences in correlation by both hardware and protocols; differences in range of motion by the Xsens accuracy. Results thus support the commencement of a clinical trial of Outwalk on transtibial amputees.


Gait analysis Kinematics Protocol Ambulatory Inertial sensors Magnetic sensors Cerebral palsy Amputee 

Supplementary material

11517_2009_544_MOESM1_ESM.pdf (114 kb)
(PDF 114 kb)


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Copyright information

© International Federation for Medical and Biological Engineering 2009

Authors and Affiliations

  • Alberto Ferrari
    • 1
    • 2
  • Andrea Giovanni Cutti
    • 1
  • Pietro Garofalo
    • 1
    • 2
  • Michele Raggi
    • 1
  • Monique Heijboer
    • 1
  • Angelo Cappello
    • 2
  • Angelo Davalli
    • 1
  1. 1.INAIL Prostheses CentreVigorso di BudrioItaly
  2. 2.Department of Electronics, Computer Science and SystemsUniversity of BolognaBolognaItaly

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