Well they couldn’t do that at first. They had to start with ~65% and work up from that. At some point they got to 75% and then later to that 85%. But also, they tested again half way through the 5 months and presumably raised their MAP accordingly.
Assuming they weren’t doing other training as well, they would have gotten really good at threshold. But maybe MAP dropped. IDK and I’m too busy to dig through the paper.