Every single day we challenge ourselves and our bodies with movements that require motor skills. We move and use both fine and gross movements to either grasp things or e.g. walking. Furthermore, there is often a correlation between motor skills and physical activity level. Our motor skills are important in many contexts and in order to be able to cope with everyday life and adapt to our surroundings and participate in various activities, we need to develop motor skills during our lives. Such skills do not arise by themselves, but require us to practice and use the skills and this leads to improvements in our movements, e.g. in that movements become more precise both in terms of the position of the joints and the force development of the muscles. However, how we practice and learn new movements also seems to be different depending on the age and thus also neurophysiological maturation processes.The purpose of this PhD thesis is to investigate the relationships between motor skills, physical capacity and executive functions in preadolescent children and then to investigate whether motor practice with an emphasis on either position control or force control leads to different effects on precision and force development in preadolescent children and young adults. This was done through the collection of data through tests of motor performance, cognitive (executive) function and physical capacity and in a cross-sectional study that included 270 preadolescent children aged 9-11 years (Study I), as well as by collecting behavioral data on motor performance, motor learning and neurophysiological data in Study II and III from 44 preadolescent children aged 9-11 years and 66 young adults aged 20-30 years respectively. Study I investigated associations between motor, cognitive and physical performance in preadolescent children between 9-11 years of age. The results demonstrate significant associations between performance in several of the measured motor skill domains and that there are associations between fine motor skills and executive functions as well as between physical capacity measured as hand grip force and executive functions. In Study II, the effects of dynamic and isometric motor practice on motor skill related behavioral and neurophysiological parameters in 9-11-year-old (preadolescents) children were investigated. The results show that preadolescent children become more precise in their position control after dynamic training, while isometric training does not lead to improvements in force control. Furthermore, the results show that there are significant but low levels of corticomuscular coherence during the hold-phase in both the dynamic and isometric version of the motor task. Following motor practice, there were however no changes in corticomuscular coherence in children at the age of 9-11y irrespective of the type of motor practice. Study III also examined the effects of motor practice on motor skills related behavioral and neurophysiological parameters, but in this study the participants were young adults. The results show improvements in both position and force control after dynamic training, while isometric training only results in improvement of force control and does not have the same transfer effect for positional control. The results also show that the dynamic practice leads to increased corticospinal excitability compared to what is observed following isometric training. Overall, the thesis contributes with new knowledge about motor skills and motor learning in preadolescent children and young adults. The results from Studies II and III contribute to a better understanding of age-related differences in motor learning, both in terms of the specific motor performance measures and in relation to underlying neurophysiological mechanisms.