Available online at www.sciencedirect.com The Foot 17 (2007) 190–196 BioFoot ® in-shoe system: Normal values and assessment of the reliability and repeatability Alfonso Mart´ ınez-Nova ∗ , Jos´ e Carlos Cuevas-Garc´ ıa, Javier Pascual-Huerta, Raquel S´ anchez-Rodr´ ıguez Departamento de Enfermer´ ıa, Centro Universitario de Plasencia, Podolog´ ıa, Universidad de Extremadura, Spain Received 6 March 2007; received in revised form 23 April 2007; accepted 24 April 2007 Abstract Background: BioFoot ® is an in-shoe system to measure plantar pressures at the interface between the shoe and the sole of the foot. Since reliability and good repeatability are necessary to ensure the consistency of measurements on which clinical judgements are based, the aim of the study was to assess the reliability and repeatability of the BioFoot ® system and identify normal values for healthy subjects. Materials and methods: Thirty subjects, 18 women and 12 men, were measured twice, with a 7–10 day interval between the sessions, wearing the same kind of shoes. In each session, three trials were recorded. The foot was divided into ten areas: heel, midfoot, whole forefoot, 1st–5th metatarsal heads, hallux, and lesser toes. Results: The intra-class correlation coefficients were between 0.76 and 0.96 for all four variables evaluated. The coefficient of variation between two sessions was around 7% (range: 4.6–9%). The mean contact time was 0.81 s, and walking cadence was 101.5 steps per minute. The pressure measurements showed the greatest peak and mean pressures under the second metatarsal head, and the second peak and mean pressures under the third metatarsal head. Conclusion: The plantar pressure measurements showed good to excellent consistency, and it was concluded that the BioFoot ® in-shoe system has good reliability and is repeatable. The highest values were found beneath the forefoot, which is consistent with the literature. © 2007 Elsevier Ltd. All rights reserved. Keywords: BioFoot ® ; In-shoe system; Reliability; Repeatability; Normal pressures 1. Introduction Plantar pressure measurement is commonly used to deter- mine specific loading characteristics at the sole’s surface of the foot. With the advent of microcomputer technology, in-shoe plantar pressure measurements have become feasi- ble. The device interferes minimally with foot function, and provide data for clinical decisions with good consistency [1–3]. In-shoe pressure data provides evidence for clinical deci- sions if the systems utilised are proven to be valid, repeatable and accurate [4]. Insole pressure systems can be used to mea- ∗ Corresponding author at: Centro Universitario de Plasencia, Avda Virgen del Puerto no. 2, 10600 Plasencia, C´ aceres, Spain. Tel.: +34 927427000; fax: +34 927425209. E-mail address: podoalf@unex.es (A. Mart´ ınez-Nova). sure the vertical force in a controlled time trial to determine the subject’s amount of weight bearing [1,2]. In addition, measurement of pressures at the foot–shoe interface gives a more realistic picture of the plantar pres- sures of subjects walking, running, or going about their daily activities. This permits clinicians to draw conclusions regard- ing which areas of the foot are under the greatest pressures in shod conditions, and could help to evaluate the therapeutics of footwear or orthotics and understand the ætiology of foot dis- eases. An in-shoe system is likely to be the system of choice when the greatest accuracy and repeatability are desired [1,4]. To attain that level of reliability it is necessary for a consistent protocol, controlling cadence and averaging multiple strides. One such in-shoe system is the BioFoot ® (Instituto de Biomec´ anica de Valencia, Valencia, Spain). It consists of two thin (0.7 mm), flexible, polyester insoles with 64 piezoelectric sensors each, allowing for dynamic plantar pressure measure- 0958-2592/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foot.2007.04.002