Objective: To investigate the reliability and validity of measures obtained from a portable electronic device used to monitor changes in plantar pressure, temperature, and humidity that occur within the shoe during prolonged activity.
Design: Descriptive study comparing electronic sensor output with criterion values.
Settings: Indoor level walkway for pressure data; uncontrolled, outdoor environment for step count data; enclosed environmental control chamber for humidity and temperature data.
Participants: Convenience sample of 4 healthy, sensate subjects.
Interventions: Not applicable.
Main outcome measures: Correlations between sensor output and criterion measures were determined for pressure and temperature data. The absolute differences between sensor output and criterion values of temperature, humidity, and step count were also determined.
Results: Pressure measurements from electronic sensors correlated highly with criterion values (r > or =.82), both before and after prolonged use. Relative humidity sensor output were within 5% of hygrometer values. In-shoe temperature data correlated highly with criterion values (r > or =.99), and differed from known temperatures by.50 degrees +/-.84 degrees C and.96 degrees +/- 1.56 degrees C at the forefoot and heel, respectively. Electronic step counts recorded at the central forefoot were within 1 step of visual step counts. Pressure tracings obtained from the device during different weight-bearing activities revealed qualitatively distinct pressure patterns.
Conclusion: The device provides valid and reliable measures of in-shoe plantar pressures, temperature, and humidity during prolonged activity.