The difference in marathon records between Korea and Japan is massive

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I was reading a news article below and got curious, so I searched for it.
Even though they are both Asians, the difference is this significant.
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Major rankings for the Women's Marathon at the 107th National Sports Festival
1st Place (Gold): Choi Jung-yoon (Chungnam Provincial Government) — 2:43:52 (2nd consecutive win)
2nd Place (Silver): Jung Hyun-ji (Samcheok City Hall) — 2:43:55 (Only 3 seconds behind 1st place)
Yada Mikuni finished 4th at the 2026 Osaka Women's International Marathon, her first marathon stage, with a time of 2:19:57. This is the all-time best record for a Japanese female athlete in a marathon debut, and it marks the sixth time a Japanese female athlete has broken the 2:20 barrier.