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1. Introduction
The mechanisms by which exercise increases nerve cell production are not clearly understood, but an increase in nerve growth factors and neurotransmitters during exercise has been suggested to play an important role. Specifically, brain-derived neurotrophic factor (BDNF) is well known to show an exercise-induced increase in expression and promote neuronal cell formation [1]. BDNF is involved in promoting the survival of progenitor cells that have the potential to differentiate into neurons or glia, as well as in differentiating these progenitor cells into neurons [2]. Neurotransmitters, such as serotonin, also show increased levels after exercise and have been reported to induce the generation of neurons [3]. In addition, various growth factors, such as vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF-1), are known to promote the production of new cells [4].
In addition, the development of image analysis techniques, such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and transcranial Doppler (TCD), has not only facilitated morphometric analysis of the brain, but has also allowed accurate confirmation of the brain regions activated by various stimulations. Among these image analysis techniques, TCD is a non-invasive method that allows real-time measurement of intracranial hemodynamics without requiring exposure to radiation and contrast agents, but it cannot visualize whole blood vessels [5]. Previous studies have suggested that regular exercise can reduce the risk of cerebrovascular and neurological diseases by increasing cerebral blood flow. Murrell et al. reported that a 12-week aerobic exercise training program significantly increased middle cerebral artery blood velocity (MCAv) in young (mean age: 23 ± 5 years) and older (mean age: 63 ± 5 years) participants [6], while Ainslie et al. reported that regular aerobic-endurance exercises were significantly correlated with high MCAv in men aged 18-79 years [7]. Studies that have examined changes in MCAv with regular exercise in children and/or adolescents during their growth period are limited; previous studies in this regard were limited to specific conditions, such as vasovagal syncope [8,9].
Taekwondo (TKD) is a martial art form that originated in Korea and has been adopted as an official Olympic sport since the Sydney Olympics in 2000. It is a popular sport worldwide, with about 80 million individuals from more than 200 countries participating [10,11]. The number of...