Purpose. To understand how athletes invest their energy over a race, differences in pacing ability between athletes with and without intellectual impairment (II) were explored using a novel field test. Methods. Well-trained runners (n=67) participated in this study, including 34 runners with II (age = 24.4 +/- 4.5 years; IQ = 63.1 +/- 7.7) and 33 runners without II (age = 31.4 +/- 11.2 years). The ability to perform at a pre-planned submaximal pace was assessed. Two 400m running trials were performed on an athletics track, with an individually standardized velocity. In the first trial, the speed was imposed by auditory signals given in 20m-40m intervals, in combination with coach-feedback during the initial 200m. The participant was instructed to maintain this velocity without any feedback during the final 200m. In trial 2, no coach-feedback was permitted. Results. Repeated measures analyses revealed a significant between-groups effect. II-runners deviated more from the target time than runners without II. The significant trial x group interaction effect (F = 4.15, p<.05) revealed that the ability to self-regulate the pace during the final 200m improved for runners without II (Trial 1: 1.7 +/- 1.0s, Trial 2: 0.9 +/-0.8s) whereas the II-runners deviated even more in Trial 2 (4.4 +/- 4.3s), than in Trial 1 (3.2 +/- 3.9s). Conclusion. Our findings support the assumption that intellectual capacity is involved in pacing. It is demonstrated that II-runners have difficulties maintaining a preplanned submaximal velocity, and this study contributes to understanding problems II-exercisers might experience when exercising. With this field test, we can assess the impact of II on pacing and performance in individual athletes which will lead to a fair Paralympic classification-procedure.