Effects of Exercise Snacks on Motor Coordination in Children with Obesity: A Pilot Randomized Controlled Trial

Abstract Background Obesity in children and adolescents has become a major global public health problem and is often accompanied by delayed development of motor coordination. Exercise snacks refers to completing multiple short, structured exercise sessions distributed throughout the day, and is more time-efficient and flexible than traditional exercise interventions. However, evidence regarding its effects on motor coordination in children with obesity remains limited. This study aimed to evaluate the effects of a 10-week school- and home-based fragmented high-intensity cordless jump rope exercise intervention on motor coordination in children with obesity. Methods A single-blind, two-arm randomized controlled trial design was used. Forty-eight children with obesity aged 6–12 years were recruited from a primary school in Shenzhen. They were randomly assigned at a 1:1 ratio to an intervention group (N = 24) and a control group (N= 24). The intervention group performed exercise snacks on 3 nonconsecutive days per week for 10 weeks. On each intervention day, participants completed three 3-minute exercise sequences (1 minute of warm-up at 50%–70% HRmax; 1 minute of high-intensity cordless jump rope at 80%–90% HRmax; and 1 minute of cool-down at ≤50% HRmax), with two sessions conducted at school and one at home per week. The control group maintained their usual lifestyle and did not receive any additional exercise intervention. Motor coordination was assessed using the Movement Assessment Battery for Children–Second Edition (MABC-2). Feasibility outcomes included study completion rate, exercise bout completion rate, exercise intensity adherence rate, and adverse events. Repeated-measures analysis of variance was used to test intervention effects according to the intention-to-treat principle, with partial eta squared (η²p) as the effect size. Results Baseline characteristics were balanced and comparable between the two groups (Pall > 0.05). The study completion rate was 91.7% (22/24) in the intervention group and 83.3% (20/24) in the control group (P = 0.666). In the intervention group, the completion rate of the 90 prescribed high-intensity exercise bouts was 94.17% ± 5.80%. Of the valid monitoring records, 85.42% (205/240) reached the prescribed intensity range. The mean monitored intensity was 81.71% ± 1.73% HRmax. No adverse events were reported during the intervention. Significant group × time interaction effects were found for the total motor coordination score (F (1, 46) = 21.87, P < 0.001, η²p = 0.32), aiming and catching (F (1, 46) = 20.49, P < 0.001, η²p = 0.31), and balance (F (1, 46) = 5.53, P = 0.023, η²p = 0.11), with greater improvements in the intervention group than in the control group (total score: +2.04 vs +0.08; aiming and catching: +1.33 vs +0.17; balance: +0.50 vs +0.04). No significant group × time interaction effect was observed for manual dexterity (F (1, 46) = 2.50, P = 0.121, η²p = 0.05). Results of the per-protocol sensitivity analysis were consistent with those of the intention-to-treat analysis. Conclusions The 10-week school- and home-based fragmented high-intensity cordless jump rope exercise intervention was feasible and improved overall motor coordination in children with obesity, with stable effects on aiming and catching and balance, but no significant improvement in manual dexterity. These findings suggest that the effects of exercise snacks on motor coordination are dimension-specific and may depend on the neuromuscular compatibility between the intervention content and the targeted motor dimensions. Future interventions should incorporate fine motor tasks into gross motor training to promote comprehensive development of motor coordination in children with obesity. Trial registration Chinese Clinical Trial Registry, ChiCTR2200066143. Registered on 25 November 2022.