Effect of starting temperature on the repeatability of thermotactile thresholds

Hand-transmitted vibration has been observed to cause a wide variety of different signs and symptoms of neurological dysfunction. Different tests of tactile sensitivity, encompassing sensations of pressure, vibration, pain and temperature have been employed in the quantification of the sensorineural effects of vibration. However, since the results of such tests are dependent on different variables, and different versions of each test are used in different laboratories, the results are rarely reported in a manner allowing a direct comparison of results between studies. This paper reports on an investigation of the repeatability of thermotactile thresholds, as used in the detection of some neurological effects of hand-transmitted vibration. In the test, the temperature of a surface increased or decreased from a fixed reference (i.e. starting) temperature at a rate of 1 degree C per second. In a group of 10 health male subjects, five measures of both warm and cool thermal thresholds were obtained with each of 5 different starting temperatures on each of 3 different days. The 'neutral zone' between the warm and cool thresholds was also calculated. The starting temperature was found to have a significant effect on warm and cool thresholds, and less effect on the width of the neutral zone. It is concluded that the starting temperature should be controlled when determining thermotactile thresholds.