How does one do a 400 TSS 4 hour ride with an IF of 1.0, yikes. That must be pro level.

The worst I can recall doing was a 2:45 Zwift race, I did just a hair under 0.90 and with the 20 minute warmup, it was a 90%. I was absolutely wrecked. Last race I ever won although zwift racing doesn't seem real.