Ethical approval for the study was obtained from the Ethics Committee of Shanghai University of Medicine and Health Sciences (Approval No. 2021-NFC-10-150203198809). The study was prospectively registered on ClinicalTrials.gov (ID. NCT06544317).
Study population and recruitment
Participants were recruited from primary schools located in three different districts of Shanghai. Before initiating the recruitment process, the researchers distributed recruitment letters to the children's parents. The letters provided the objectives of the study, its significance, and methodology, along with a consent form. Parents who agreed to participate were asked to sign a consent form and complete an online questionnaire accessible via a QR code. The information included the Developmental Coordination Disorder Questionnaire (DCDQ), the ADHD Rating Scale-VI, and other demographic information about participants. Questionnaire responses were accessible only to the research team. The lead researcher's contact details were also provided in the form to address parents' inquiries.
A total of 2,761 children and their parents volunteered to be included in this study. The children were initially screened with the Developmental Coordination Disorder Questionnaire (DCDQ)17,18. Based on teachers’ assessments, those identified as potentially having pDCD but showing no signs of intellectual or cognitive impairments were selected for further evaluation. These candidates subsequently underwent an assessment using the Movement Assessment Battery for Children, Second Edition19. A total of 194 children were identified as potential pDCD candidates during screening. After exclusion of 78 children who did not meet the eligibility criteria, 116 children met the study criteria for pDCD and were randomly allocated to either a training group (TG; n = 58) or a control group (CG; n = 58) using computer-generated random number allocation performed by an independent researcher not involved in outcome assessment. Allocation results were concealed from outcome assessors during baseline and post-intervention testing. In addition, a group of typically developing children (TD; mean age 10.35 ± 1.87 years; 48 boys and 12 girls) was included as a comparison group, matched for gender. Both the TG and TD groups participated in a 12-week physical training program, whereas the CG group did not undergo any training intervention. An overall schematic representation of the study design and experimental workflow is presented in Figure 1.
Eligibility criteria
The inclusion criteria used for the group of children who had pDCD were as follows: (1) DCDQ scores as follows: 8–9 years: < 56 points; 10–12 years: < 58 points; (2) identification of motor problems using Movement Assessment Battery for Children, Second Edition (MABC-2) (a percentile rank below 15% in at least one subitem of the MABC-2); (3) age 9 to 11 years old (elementary school age); (4) children with known intellectual disability, neurological disorders, or clinically diagnosed cognitive impairment reported by school records, parents, or teachers were excluded from participation; (5) no reports or history of other neurodevelopmental conditions (e.g., ADHD) by parents. Before testing, the researchers ensured that the parents filled out the Attention Deficit/Hyperactivity Disorder (ADHD) Rating Scale-VI20. Children whose ADHD Rating Scale-VI scores exceeded the age- and sex-adjusted 98th percentile cutoff were excluded from participation, per established screening criteria for ADHD21. Children included in the TD group additionally met the same exclusion criteria applied to the pDCD group, including absence of ADHD, neurological disorders, intellectual disability, or other neurodevelopmental conditions.
The second edition of the Movement Assessment Battery for Children (MABC-2) is intended for use with children aged 3–16 years19. It comprises eight specific tasks that assess a range of abilities. This includes fine motor control, gross motor skills, balance, and related functions. Each task produced a raw score, which was standardized for the child’s age. These standardized scores are summed across three subcomponents to calculate a motion subdomain score. A higher score indicates better motor coordination. The MABC-2 has shown strong internal consistency (α = 0.90) and reliable test–retest total scores (ICC = 0.97)22, in addition to demonstrating discriminant validity for identifying motor disorders23.
Randomization and group allocation
All the children were right-handed, as assessed using the Edinburgh Handedness Scale24. A total of 116 children with pDCD (98 boys and 18 girls) and 60 TD children (48 boys and 12 girls) were included in the final analysis. Details regarding participant screening, eligibility assessment, randomization, and group allocation are provided in the Study Population and Recruitment subsection and summarized in Figure 1.
Assessment personnel and blinding
The experimental setup of this study was carefully designed according to the standard assessment tool, MABC-2, and the experimenters were trained and licensed researchers. The entire study was conducted in consultation and collaboration with sports rehabilitation experts with pDCD training experience. The coaches and trainers in the study were physical education teachers with more than 5 years of teaching experience. Each group had ten children, with one coach explaining the movements and two caring for the children during training. Five undergraduate physical therapy students were present for all the tests to ensure that the participants in the two tests were identical. Outcome assessors responsible for cognitive and physical fitness testing were blinded to participant group allocation. Due to the nature of the exercise intervention, coaches supervising training sessions could not be blinded.
Testing schedule
All pretests were completed within three days before the children started the exercise intervention, while post-tests were completed within three days after the last training session (depending on the group's training time). This study used a prospective controlled intervention design.
Procedure
The study evaluated 176 participants (116 children with pDCD and 60 TD children) on cognitive and physical fitness assessments before and after the intervention. Refer to Table 1 for the motor skills training program. A series of 90 min after-school physical training sessions, three times a week for 12 weeks, was administered. Each session began with a 20 min warm-up, followed by 60 min of three or four tasks targeting the specific skill to be developed (aerobic training, resistance training, motor skills and balance activities, stretching and flexibility exercises, and core strength and posture exercises), and concluded with a 10 min cool-down. The children were divided into six groups, each consisting of eight to twelve participants. The intervention program was standardized across sessions and progressively adjusted according to participant tolerance and motor performance. Exercise intensity was monitored by supervising physical education teachers using session completion and participation monitoring. Attendance was recorded throughout the intervention period.
Testing procedures and instrumentation
Physical fitness and anthropometric measures
Three physical fitness tests were conducted, including the standing broad jump (SBJ), the 50 m sprint, and the 50 m × 8 shuttle run25. Students were instructed to start in a standing position and complete the 50 m sprint with maximum effort. The test was performed twice, and the fastest result was recorded. The SBJ test was administered on a flat surface to test the explosive strength of the lower limbs. The shuttle run was used to assess children’s speed, agility, and endurance26; children were instructed to run back and forth between two points as quickly as possible. The participants' heights were measured to the nearest 0.1 cm with a stadiometer, and their weights were measured to the nearest 0.1 kg with the same device. Children were weighed in light school uniforms without shoes, and all anthropometric measurements were performed by the same trained assessor.
Cognitive function
Cognitive tasks were computerized and administered in a standardized laboratory setting. Reaction time and response accuracy were recorded for each trial. Participants completed familiarization trials before formal testing. Stimulus presentation order was randomized across trials.
Mental rotation tasks
Children were instructed to use object-based mental rotation strategies by keeping their bodies still and mentally manipulating visual stimuli from a stationary perspective to apply object-based transformations27. Two pictures of “giraffes” were presented simultaneously, with the left image fixed as the main focus while the right image displays angular or mirror differences. Set angular disparities at 0°, 60°, 120°, or 180°. Children were asked to determine, as quickly and accurately as possible, if the two images were identical.
Modified Stroop task
A computerized modified Stroop task, with two conditions: naming (non-execution) and execution, was used28. In the naming condition, display a colored “XXX” on the screen and instruct children to press the key corresponding to the displayed color. In the execution condition, present a distracting-colored Chinese character in blue or red, and instruct children to press the key matching the color of the word rather than its meaning. Define the condition as congruent when the color and meaning are consistent, and incongruent when they are inconsistent.
Statistical analysis
Physical fitness analyses
A mixed-design analysis of variance (ANOVA) was conducted for each variable, with three groups (TG, CG, and TD) completing pre- and post-test measurements to determine the efficacy of the school-based exercise intervention. In physical fitness tests, a 3 × 2 (Group [TG, CG, and TD] × Time [baseline and post-intervention]) mixed-design repeated-measures ANOVA was used to analyze the results. Paired t-tests were also used to assess each group's results before and after the intervention. Post-hoc pairwise group comparisons were conducted following significant ANOVA effects.
Statistical assumptions
Normality of data distribution was assessed using the Shapiro–Wilk test, while homogeneity of variance was evaluated using Levene’s test. Sphericity assumptions for repeated-measures factors were examined using Mauchly’s test, and Greenhouse–Geisser corrections were applied when violations of sphericity were detected.
Cognitive task analyses
Computerized cognitive testing software was used to collect reaction time and correct rate data in children's cognitive tasks. All incorrect trials and trials with more than three standard deviations were removed as outliers. A 3 × 2 × 2 mixed-design ANOVA (Group [TG, CG, and TD] × Time [baseline and post-intervention] × 2 Conditions [non-executive conditions, and execution conditions]) mixed-design analysis was conducted to examine the RT and correct rate in the Stroop task for each group. In the mental rotation tasks, a 3 × 2 × 4 mixed-design ANOVA (Group [TG, CG, and TD] × Time [baseline and post-intervention] × Angular disparity [0°, 60°, 120°, or 180°]) was conducted to assess reaction time and error rate variables. Post hoc pairwise comparisons were performed, where appropriate, following significant interactions or group effects. Before the formal experiment, children were made familiar with the testing procedures and were asked to practice them a certain number of times. When the accuracy reached 75%, the test began; across all conditions, the study did not observe a notable difference in accuracy between the two groups. Finally, the researchers set the significance threshold to p < 0.05. Effect sizes were reported using partial eta squared (η2). The researchers analyzed and statistically compared all data using statistical analysis software.