title: A new insole measurement system to detect bending and torsional moments at the human foot during footwear condition: a technical report.
abstract: BACKGROUND
  Stress occurring at the feet while wearing footwear is often determined using pressure measurement systems. However, other forms of stress, such as bending, torsional and shear loadings, cannot be detected in shoes during day-to-day activities. Nevertheless, the detection of these types of stresses would be helpful for understanding the mechanical aspects of various kinds of hard and soft tissue injuries. Therefore, we describe the development of a new measuring device that allows the reliable determination of bending and torsional load at the foot in shoes.
  
  
  METHODS
  The system consists of a measuring insole and an analogue device with Bluetooth interface. The specific shape of the insole base layer, the positions of the strain gauges, and the interconnections between them have all been selected in such a way so as to isolate bending and torsional moment detections in the medial and lateral metatarsal region. The system was calibrated using a classical two-point test procedure. A single case study was executed to evaluate the new device for practical use. This application consisted of one subject wearing neutral shoes walking on a treadmill.
  
  
  RESULTS
  The calibration results (coefficients of determination R(2) > 0.999) show that bending and torsional load can be reliably detected using the measurement system presented. In the single case study, alternating bending and torsional load can be detected during walking, and the shape of the detected bending moments can be confirmed by the measurements of Arndt et al. (J Biomech 35:621-8, 2002).
  
  
  CONCLUSIONS
  Despite some limitations, the presented device allows for the reliable determination of bending and torsional stresses at the foot in shoes.
authors.affiliation: Registered Association for the Encouragement of Research and Education Management in Orthopedic Footwear Technologies Germany, Ricklinger Stadtweg 92, D-301459 Hannover, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Stief
authors.affiliation: Biomechanics Research Laboratory, Münster University of Applied Sciences, Bürgerkamp 3, D-48565 Steinfurt, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Peikenkamp
keywords: Foot; Force, Torsional; Forefoot, Human; Gait; Orthopedics; Running; Shoe; Stress, Mechanical; Torque