A DEVICE FOR SIMULTANEOUS MEASUREMENT OF PRESSURE AND SHEAR FORCE DISTRIBUTION ON THE PLANTAR SURFACE OF THE FOOT

A device has been designed to simultaneously measure the vertical pres sure and the anterior-posterior and medial-lateral distributed shearin g forces under the plantar surface of the foot. The device uses strain gauge technology and consists of 16 individual transducers (each with a surface area measuring 2.5 x 2.5 cm) arranged in a 4 x 4 array. The sampling frequency is 37 Hz and data may be collected for 2 s. The de vice was calibrated under both static and dynamic conditions and revea led excellent linearity (+/-5%), minimal hysteresis (+/-7.5%), and ver y good agreement between applied and measured loads (+/-5%). Vector ad dition of the distributed loads gave resultant forces that were qualit atively very similar to those obtained from a standard force plate. Da ta are presented for measurements from the forefoot of 4 diabetic subj ects during the initiation of gait, demonstrating that distributed she ar and pressure on the sole of the foot can be measured simultaneously .