Monitoring in-shoe plantar pressures, temperature, and humidity: Reliability and validity of measures from a portable device

Objective: To investigate the reliability and validity of measures obtained from a portable electronic device used to monitor changes in plantar press ure, temperature, and humidity that occur within the shoe during prolonged activity. Design: Descriptive study comparing electronic sensor output with criterion values. Settings: Indoor level walk-way for pressure data; uncontrolled, outdoor en vironment for step count data; enclosed environmental control chamber for h umidity and temperature data. Participants: Convenience sample of 4 healthy, sensate subjects. Interventions: Not applicable. Main Outcome Measures: Correlations between sensor output and criterion mea sures were determined for pressure and temperature data. The absolute diffe rences between sensor output and criterion values of temperature, humidity, and step count were also determined. Results: Pressure measurements from electronic sensors correlated highly wi th criterion values (r greater than or equal to .82), both before and after prolonged use. Relative humidity sensor output were within 5% of hygromete r values. In-shoe temperature data correlated highly with criterion values (r greater than or equal to .99), and differed from known temperatures by . 50 degrees+/-.84 degreesC and .96 degrees +/- 1.56 degreesC at the forefoot and heel, respectively. Electronic step counts recorded at the central for efoot were within 1 step of visual step counts. Pressure tracings obtained from the device during different weight-bearing activities revealed qualita tively distinct pressure patterns. Conclusion: The device provides valid and reliable measures of in-shoe plan tar pressures, temperature, and humidity during prolonged activity.