## 4 Discussion
The reason for the improvement in the updating function of the intervention group may be that during the coordinated exercise training process, the children were asked to do shuttle runs, forehand-backhand hits, and run around a mark, etc. These practices require children to update an action rapidly and frequently. For example, the children had to run from the right to left of the mark when running around it and this type of activity requires them to make quick adjustments and could be beneficial for the updating ability in the spatial WM. The fNIRS results obtained herein showed that in comparison with the control group, the experimental group demonstrated a large hemoglobin concentration increase in the prefrontal cortex from the pre-test to post-test. In accordance with the present results, [PERSON] et al. [45] observed oxy-Hb signal increases associated with the Stroop interference in the left dorsolateral prefrontal cortex (DLPFC) after a bout of moderate exercise. They postulated that the increased level of wakefulness caused by acute moderate exercise may be the reason for increased activation of the left DLPFC in cognitive performance. [PERSON] et al. [46] also found that fatigue and sleepiness may lead to decreased LPFC activation, although such effects in WM have yet to be explored. Furthermore, [PERSON] et al. [47] revealed that older participants with higher aerobic fitness exhibited a higher oxy-Hb signal amplitude in the dorsolateral PFC when performing a color-word Stroop task, which indicated that high aerobic fitness is associated with increased oxygen supply to the dorsolateral PFC. Another possible reason for these results may partly be explained by the psychomotor efficiency theory. After exercises, the physiological system of the human body usually manifests itself in minimizing the amount of energy consumed to complete the maximum workload; that is, the effectiveness of the various systems of the body is improved. The oxy-Hb signal climbed in the prefrontal cortex indicated that the neural resources were more concentrated in the cognitive task after eight weeks of coordinative exercise training. Specifically, less attentional demand and less cognitive interference with motor planning and execution were needed when performing a task [48], which supports the view that coordinative exercises benefit the allocation of attention resources and stimulate the evaluation speed [49], as well as enhance the activation in the PFC [16]. Given that frontal brain electrical activity can predict working memory performance at age 4-12 years [50], it is possible that coordinative exercises may alter the prefrontal cortex, which in turn influences its function. In this study, since the physical fitness of the experimental group improved after the proposed exercise, coordinative exercises may affect the updating ability of the WM in young children via the improvement of physical fitness. Indeed, previous studies showed that aerobic fitness training increased hippocampal volume in elderly humans, which is correlated with better spatial memory performance [51; 52]. Furthermore, [PERSON] et al. [53] suggested that the hippocampal volume is modulated by aerobic exercise throughout the lifespan. The mediating role of physical fitness can be tested by the structural equation model based on a large sample size in the future. Another possible explanation for this relationship between the coordinative exercises and the updating function of WM might be that both these variables were involved in the cerebellum. Accumulative evidence has shown that the cerebellum plays an important role in WM. [PERSON] et al. [54]utilized an adapted Corsi-block task to investigate visual WM in patients with cerebellar ischemic stroke, and they suggested that the cerebellum controls the incoming visual WM information. Other studies [17; 54] used a 3-back task to measure the WM of adults and found that the reaction speed in the task is linked to structural variation in both motor and cognitive subregions of the cerebellum.