At 5 years of age, both the short version of the Revised Amsterdam Intelligence Test (RAKIT) and the Movement Assessment Battery for Children (MABC) were adminis- tered, as described previously [17]. For the RAKIT [18], the mean (SD) score of the normative population is 100 (15). The MABC [19] presents a total impairment score (TIS) and three subtest scores: manual dexterity, ball skills, and balance skills. The MABC test results are expressed in percentiles, which we clustered into normal (Np15), borderline (p6-p15), and definite motor problem (≤p5). The maximal exercise capacity was tested with the Bruce treadmill protocol at 5 years of age. This yielded a maximal endurance time which was converted to SDS using recently published Dutch reference values [20].