Association between physical exercise based on FITT principle and vision health among primary school students in Suzhou, China

Objective This study aimed to examine the association between physical exercise based on the FITT principle (frequency, intensity, time, and type) and vision health, including uncorrected distance visual acuity (UDVA) and kinetic visual acuity (KVA) among Chinese primary school students. Methods A total of 1,649 students from grades 2 to 5 across five primary schools in Suzhou, China, were selected as the study participants. Information on physical exercise, including frequency, intensity, time, and type, was collected using structured questionnaires. Exercise volume was additionally calculated to reflect overall physical activity exposure. Data on eye usage habits, visual environments, and outdoor activity time were also collected. UDVA and KVA were assessed using a standard logarithmic visual acuity chart and a kinetic visual acuity tester, respectively. Generalized Propensity Score Matching (GSPM) was employed to estimate the associations between exercise frequency, intensity, time, volume, and the UDVA and KVA of the students. Additionally, the traditional Propensity Score Matching (PSM) was applied to examine the associations between different types of exercise and the students’ UDVA and KVA. Results No significant gender difference was found in UDVA ( p > 0.05), whereas KVA varied significantly by gender ( p < 0.05). Additionally, both metrics showed significant differences across grade levels ( p < 0.05). The associations between exercise frequency, intensity, time, volume, and the students’ UDVA and KVA exhibited an “inverted U-shaped” pattern. Moreover, participation in open-skill sports was associated with more favorable UDVA compared with closed-skill sports. Conclusion Among students in grades 2 to 5 in Suzhou, UDVA declined progressively with increasing grade level, while KVA peaked in grade 4 and subsequently declined. The more positive associations with both UDVA and KVA were observed among primary school students engaging in physical exercise 3 to 4 times per week at moderate intensity and moderate volume. Exercise durations of 61 to 90 min per session and 91 to 120 min per session showed the more significant correlation with higher levels of UDVA and KVA, respectively. Additionally, open-skill sports were more significantly associated with the healthy development of UDVA compared to closed-skill sports.