Not All Forms of Exercise Lead to Positive Affect: A Comparative Monitoring Between an Imposed and Self-Adjusted Prescription in Recreational Runners—A Cross-Sectional Randomized Controlled Study

Objective: To evaluate the affective responses to running with imposed velocity or self-selected time trials in runners, as well as the effects on volume load (VL) and training impulse (TRIMP). Anxiety was also determined. We established the level of association between the dependent variables. Methods: Three visits were carried out. The 1st visit consisted of a maximum running effort test (VO2Max). In the 2nd and 3rd visits, participants were divided between the time limit (TLim) or time trial 1000 m running at self-selected intensity (T1000). Participants responded to the felt arousal, feeling, and anxiety SUDS scale before, during, and after TLim and T1000. Results: TLim vs. T1000 (p < 0.001) and VPeak × V1000 (p = 0.013) showed differences, but did not influence VLTLim vs. VL1000 (3181.34 ± 872.22 vs. 3570.60 ± 323.3; p = 0.062). TRIMP showed no differences (p = 0.068). Arousal did not differ between the pre-exercise (p = 0.772) and post-exercise (p = 0.083) conditions but was different during (p = 0.035). There were differences between groups in the pre-exercise (p = 0.012), during (p < 0.001), and post-exercise (p < 0.001) conditions for feeling and anxiety scores. The correlation between TRIMP and affective scores showed an association with TLim (r = 0.46; p = 0.043). Conclusion: The self-selected exercise generated positive affective responses, but the same did not occur for the imposed TLim. VL and TRIMP presented equality. There was association between TRIMP and the TLim feeling scale. TLim significantly increased anxiety scores.