Introduction: The Developmental Model of Sports Participation proposes two distinct pathways towards reaching an expert level of performance: early specialization and early diversification. This study investigated the effect of sampling various sports and of the amount of time spent in sports on physical fitness and gross motor coordination. Methods: The basic performance characteristics of 735 boys aged 6–12, divided into three age groups (6–8: n=161, 8–10: n=310, 10–12: 264) were assessed by a test battery containing anthropometrical, physical fitness and coordinative tests. Data on sports participation were obtained through the use of the Flemish Physical Activity Computerized Questionnaire. Results: In the eldest age group, (M)ANCOVA showed better strength, speed, agility, endurance and gross motor coordination (p<0.05) for boys participating in various sports versus in a single sport while an effect of many hours spent in sports was apparent from the youngest age group on. Also in the eldest group, a post hoc analysis revealed that boys spending many hours in various sports were the strongest (p<0.05) and possessed the best gross motor coordination (p<0.001). Discussion: A slow and rapid performance improvement is associated with early diversification and early specialization respectively. Therefore, the importance of spending many hours in various sports towards the development of physical fitness and gross motor coordination was highlighted in this study.