The first time

This story starts way back, about 5 years ago when I was 8 years old.  My Swim coach told us that we had to swim 400 meters. I was confused, and completely gobsmacked. I had no idea why she would make us swim such a large distance at that age. I can easily swim that distance now. About at the 150 meters mark I started to feel the burn, no, like I actually felt a burning sensation in my legs and arms. I was in pain. At the end I was exhausted but relieved that it was over. Over a month later she told us to the same thing again.