Thermal pain tolerance depends on stimulus duration and thermode type

Quantitative Sensory Testing (QST) allows researchers and clinicians to evaluate variations in acute pain and thermosensation within and across individuals. However, it is unclear how experimental factors, such as thermode type and stimulation duration, affect pain measurements. We compared three types of thermodes at two stimulus durations to assess potential impacts on QST outcomes.Across two experiments, a total of 83 (45 and 38 respectively) healthy volunteers each completed two QST tasks that varied in thermode type (ATS, CHEPS or T03) and/or stimulus duration (8s or 3s), with order counterbalanced across participants. In each task, heat was applied to 8 sites on the left volar forearm for three runs (24 trials in total) and temperatures were selected through an adaptive staircase calibration procedure. Pain threshold, tolerance, and the strength of the correlation between stimulus temperature and pain ratings (r²) were estimated using linear regression. Results indicate that briefer stimuli were associated with higher pain tolerance (t = -3.28, p = 0.018), while there was no effect of duration on threshold or temperature-rating correlation. Thermode type influenced pain tolerance in short (3s) (t = -3.10, p = 0.01) but not long (8s) durations, such that on 3s trials, tolerance was higher with the smaller surface thermode (T03) compared to the larger surface thermode (CHEPS), consistent with spatial summation. No sex differences were found. These results demonstrate that suprathreshold pain tolerance, but not threshold, is sensitive to stimulus duration and thermode type. These findings also indicate the importance of methodological standardization in QST and the careful selection of suprathreshold pain stimuli in experiment design.