An examination of five theoretical foundations associated with localized thermosensory testing

Abstract

Purpose: To assess five theoretical foundations underlying thermosensory testing using local thermal stimuli.

Methods: Thermal sensation, discomfort and the confidence of thermal sensation scores were measured in 9 female and 8 male volunteers in response to 17 physical contact temperature stimuli, ranging between 18-42 °C. These were applied to their dorsal forearm and lateral torso, across two sessions.

Results: Thermal sensation to physical temperature relationships followed a positive linear and sigmoidal fit at both forearm (r² = 0.91/r² = 0.91, respectively) and lateral torso (r² = 0.90/ r² = 0.91, respectively). Thermal discomfort to physical temperature relationships followed second and third-order fits at both forearm (r² = 0.33/r² = 0.34, respectively) and lateral torso (r² = 0.38/r² = 0.39, respectively) test sites. There were no sex-related or regional site differences in thermal sensation and discomfort across a wide range of physical contact temperatures. The median confidence of an individual's thermal sensation rating was measured at 86%.

Conclusion: The relation between thermal sensation and physical contact temperature was well described by both linear and sigmoidal models, i.e., the distance between the thermal sensation anchors is close to equal in terms of physical temperatures changes for the range studied. Participants rated similar thermal discomfort level in both cold and hot thermal stimuli for a given increase or decrease in physical contact temperature or thermal sensation. The confidence of thermal sensation rating did not depend on physical contact temperature.

Keywords: Confidence; Experimental design; Thermal discomfort; Thermal sensation; Thermosensory.

Fig. 1

Thermal sensation (left), sensation confidence (middle) and thermal discomfort (right) scales. Extremely cold is 0-mm and extremely hot is 200-mm on the visual analogue scale. 0% confident is 0-mm and 100% confident is 200-mm on the visual analogue scale. Comfortable is 0-mm and extremely uncomfortable is 200-mm on the visual analogue scale. Distances between anchors are equal

Fig. 2

Relationship between applied physical temperature and thermal sensation. Panel a and b demonstrate linear (blue) and non-linear (4LP-sigmodial) (red) regression lines of thermal sensation in forearm (a) and torso (b). Panel c and d demonstrate individual data and box and whiskers with median connection line of thermal sensation in forearm (c) and torso (d)

Fig. 3

Relationship between applied physical temperature and thermal discomfort. Panel a and b demonstrate second (quadratic) (blue) and third (cubic) (blue) order polynomial regression lines of thermal discomfort in forearm (a) and torso (b). Panel c and d demonstrate individual data and box and whiskers with median connection line of thermal discomfort in forearm (c) and torso (d)

Fig.4

Correlation between thermal sensation and discomfort. Panel a demonstrates correlation between thermal sensation and discomfort in forearm. Panel b demonstrates correlation between thermal sensation and discomfort in torso

Fig. 5

Individual data and box and whiskers with median connection line of the confidence of thermal sensation ratings in forearm (a), and in torso (b)