Irish 800 record holder Louise Shanahan (1:59.42 pb) ran a 2:08 sb for 6 straight seasons (ages 16-21), before breaking out

Reminds me of Brandon Miller's progression:

2014 | 2:06.18
2015 | 1:56.41
2016 | 1:55.63 *
2017 | 1:49.87 (HS frosh)
2018 | 1:49.55
2020 | 1:49.35 (HS senior)

2021 | 1:44.99 (TAMU frosh)

People don't improve that much without a major change, be it training or other. Maybe its the shoes...

I've experienced this same meme. Running for a couple years and then one season had very minimal improvement. Then I get in a fast race and suddenly I became Superman. I took 13 seconds from the 1600. 17 if you don't include what I did that season.

Alison Andrews Paul was stuck on 2.06 for years and has just dropped to 2.01 sometimes it just clicks especially with females.

Leave it to rojo to leave out the context. She didn't just jump from 2:08 to 1:59 in one season as his post implies. Here is the rest of the progression:

2018
2:08.56
Sacramento, CA (USA)
17 MAR 2018
2019
2:04.77
Belfast (GBR)
22 JUN 2019
2020
2:04.37
Lee Valley Athletics Centre, London (GBR)
29 AUG 2020
2021
2:01.44
Mary Peters Track, Belfast (GBR)
29 MAY 2021
2022
1:59.42
Mary Peters Track, Belfast (GBR)

National vests all along the way, from 2013 onward, including the Olympics last year. She also progressed her 1500 from 4:51 to 4:33 during the plateau of the 800. She clearly benefited from the move to England to break out. This isn't exactly "rags to riches", just a nice progression. It is a good lesson for young women in particular who go through a lot of changes and stalls in late teens before full maturation.

Looking at her 1500 progression over the same time, it looks as though she has significantly changed her training to be more aerobic based:
2017 4:44.8
2018 4:33.77
2020 4:18.42
2021 4:15.27
2022 4:13.27

800 seems to be the event that has the biggest variation in training. Some train like sprinters, some like 10k runners. I could be wrong, but I would guess she's changed her training a lot. Otherwise perhaps she just finally got a good run with no injuries or illness, which might also explain the even bigger jump over the longer stuff as that is where consistency shows

She did not suddenly go to from 2:08 to 1:59 though.

Took another 4 years to gradually get down

This is her progression

Yeah the big jump was from 2:08 to 2:04 actually, which is a huge jump after a long plateau. The wild thing is in 2019 and she ran the 2:04, but every other clocking (before and after) was 2:08 or slower. I wonder if some of this is just how she runs or they type of races she's in. I can't think of anyone else who races that often at 800 and would have an SB 3+ seconds faster than every other performance (unless if it was the last race of their season possibly and a huge breakthrough).

There were 13 races at 800 (indoors and outdoors), so this wasn't a sample size thing.

It’s a pretty common thing, particularly in the development of female runners, to plateau (even regress), during late adolescence, and then see huge improvements in the early to mid-20s. Greater awareness of this biological pattern needs to be raised, so that young girls don’t become demoralised and give up the sport.

I wonder if she will take off another 9 secs in the next 4 years. Everything can be explained by training, shoes or just dedication. Even another 3 seconds would raise eyebrows.