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ObjectiveTo investigate the effect of multi-target transcranial direct current stimulation (tDCS) and single-target tDCS on the performance of working memory-postural control dual-task in healthy adults, and to compare the regulatory effect of the two stimulation protocols. MethodsFrom November, 2020 to February, 2021, 19 healthy adults in Shanghai University of Sport were recruited and randomly accepted multi-target tDCS, single-target tDCS and sham stimulation with at least one week interval between any two stimulation protocols. The target areas of multi-target tDCS included left dorsal lateral prefrontal cortex (L-DLPFC) and bilateral primary motor cortex (M1), and single-tDCS only applied to L-DLPFC. Before and after stimulation, participants completed walking and standing balance tests under single task and dual-task conditions with the second task being a N-back task. The dual-task postural control performance, dual-task cost (DTC) and working memory performance were observed before and after stimulation. ResultsSignificant differences were observed among three stimulation protocols in the changes of stride variability (F = 3.792, P = 0.029), DTC of stride variability (F = 3.412, P = 0.040) and velocity of center of pressure (Vcop) (F = 3.815, P = 0.029). The stride variability (P = 0.047) and Vcop (P = 0.015) were significantly lower and the decrease in DTC of stride variability tended to be significant (P = 0.073) following multi-target tDCS, as compared to sham stimulation. Single-target tDCS significantly decreased the changes of stride variability (P = 0.011), DTC of stride variability (P = 0.014) and Vcop (P = 0.025), as compared to sham stimulation. Compared with single target tDCS, multi-target tDCS reduced the changes of the dual-task cost of the area of center of pressure (P = 0.035). Moreover, no significant difference was observed among the three stimulation protocols in the changes of each measure in the working memory test (P > 0.05). ConclusionBoth multi-target tDCS and single-target tDCS can improve the performance of working memory-postural control dual-task in healthy adults, and compared with single-target tDCS, multi-target tDCS has some advantages in regulating postural control.
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Objective@#To measure the body mass index (BMI) of secondary school students and analyze its association with the physical fitness index, so as to improve the physical health of middle school students.@*Methods@#Using a randomized cluster stratified sampling method, 3 813 secondary school students from six cities (Ganzhou, Ji an, Fuzhou, Nanchang, Shangrao and Jiujiang) in Jiangxi Province, China, were selected in September 2022. Questionnaire survey was administered to obtain basic information and to assess the nutritional status and physical fitness tests were conducted among secondary school students. The study was stratified by gender and age, and the Kruskal Wallis H test was used to compare the differences in the mean values of grip strength, sit-ups, standing long jump performance and strength quality among secondary school students with different BMI levels, while the correlation between BMI and strength quality index was inferred by using curve regression analysis.@*Results@#There was statistical significance in the strength quality index of middle school students with different BMI level ( H=56.79, 8.84, P <0.05). Except 13 years old group, the difference of physical fitness by BMI grade strength quality index of boys in other age groups was statistically significant ( H =22.21, 16.23, 17.98, 18.21, 8.08), while the difference of physical fitness by BMI of girls at 14 years old was statistically significant ( H =9.11)( P <0.05). The curve fitting using regression showed that the physical fitness index and BMI of middle school students (boys and girls) show an inverted U-shaped curve. The physical fitness index was higher in the middle region of BMI ( Z-score) and lower in the two end regions, while showing a decreasing trend from the middle to the two ends.@*Conclusion@#An association is found between BMI and physical fitness among secondary school students in Jiangxi Province, and wasting and overweight/obesity are negatively correlated with physical fitness. Greater attention should be paid to the nutritional status of secondary school students to ensure the normal development of physical fitness.