The aim of this study was to analyse pacing strategy and emotional regulation during intermittent 3-min runs. 127 school participants performed 2 exhaustive intermittent 3-min runs at different days. The effort, the pleasure, the desire to continue, the desire to stop and the level of resources were measured every 100m with Likert scales from 0 to 10. The CONTROL group was asked to realize 2 runs as fast as possible without any other consign. The RPE group was asked to realise the first run with the same consign but has to start the second run at a minimal RPE level corresponding to the average RPE of the first run. For this, subjects were asked to self-select the intensity which induced the expected RPE. Then, exercise is totally self-paced. The strategy, which consists in a slow start with an increase of speed at the end, could be observed, for each test of each group. Fluctuations of running intensities exist, except during the second run of the RPE group. An important emotional reserve was observed in each condition. But this reserve was lower during the second run for the RPE group, contributing to the increase in performance during the second run for the RPE group (+13.5%), whereas it was not significantly different for the CONTROL group. For each group and each test, effort, affective balance and desire to stop significantly increased between the first and the last repetition, whereas pleasure, desire to continue and available resources significantly decreased during running. The most important observation is that the emotional pattern corresponded to a linear evolution in each condition whereas exercise is self-paced. This highlights that emotional regulation is a part of pacing strategy. Finally, we define the motivation to pursue a tired exercise as the level of acceptance of effort. We propose that the ratio between the desire to continue and the level of effort could be considered as a good marker of the motivation in this context.