BackgroundGood motor skills are considered important for children’s physical, social, and psychological development, but the relationship is still poorly understood. Preschool age seems to be decisive for the development of motor skills and probably the most promising time-window in relation to preventive strategies based on improved motor skills. This research program has four overall aims: (1) investigation of the effect of a structured program aimed at improving motor skills in 3–6-year-old children on current and future motor skills, health, cognition, and wellbeing; (2) establish reference data on motor skills in 3–6-year-olds; (3) description of early development of musculoskeletal problems; and (4) establishment of a population-based cohort of 3–6-year-olds.MethodsOver a four-year period, all preschools in a Danish municipality, Svendborg, will implement a new program aimed at optimizing children’s motor skills. By introducing the program into a subset of the preschools at onset and comparing these children to another subset (control) that will not receive the intervention the first three years, it is possible to document a potential effect of the intervention. At the same time, a cohort will be established including all children attending preschools in the municipality with extensive baseline data collection: gross and fine motor skills; movement patterns; musculoskeletal complaints; physical activity; anthropometry; general wellbeing; cognitive abilities; language status; medical history; demographic background; and more.The children are aged 3–6 years at baseline. A total of 1461 children have been invited into the cohort, 368 to the intervention arm and 359 to the control arm. Follow-up time for the trial is 2.5 years. The cohort is planned to run at least until the children leave school at age 15–16 years. Longer follow-up will depend on future funding.DiscussionIf the results of the trial are positive, the intervention can be implemented in other similar settings with reasonable ease and at a relatively low initial cost. This is due to the extensive end-user involvement, the broad population base, and the pragmatic nature of the intervention. The cohort will provide important information about the influence of early motor skills on children’s development across many domains and the potential interactions between these domains.Trial registrationISRCTN registry, ISRCTN23701994. Registered on 13 October 2016.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-017-2143-9) contains supplementary material, which is available to authorized users.

The preschool age seems to be decisive for the development of motor skills and probably the most promising time-window in relation to improvement of motor skills. This trial investigates the effect of an intensive structured intervention to improve motor skills in 3–6-year-old preschool children. A total of 471 Danish preschool children participated in a cluster randomized controlled trial. The intervention was to enhance motor skills, including predefined minimum criteria. Motor skills were measured using the Motor Assessment Battery for Children-2 (MABC-2) (total and three domains) at baseline and 6-, 18-, and 30-months post-intervention. The effect was estimated by multilevel linear regression with preschool and child included as random effects and adjusted for baseline values. Effect estimates were mainly positive at 6 months, but negative at 30 months with very few statistically significant estimates. In preschools with baseline motor skills scores below average, there was a tendency towards a larger improvement in the intervention group. Future interventions and research should focus on clusters with poor motor skills, as there is larger room for improvement. It remains to be seen whether the intervention can influence general well-being, physical activity, and self-perceived competence, both short- and long-term.