Yesterday I went out for my first back to back-to-back training. I cycled about 37km and ran 11km immediately after. This is more or less the distances in an Olympic triathlon. It went better than expected. Maybe I didn't push the bike hard enough? Only the first 2 minutes of running felt a bit strange. And obviously after running only 5km, you already feel tired like you'd run much more. It took me 2h10 overall (1h18'+2'+50'), which is not great, but OK for a start. I've got to improve the cycling quite a bit.

Ultra triathlon training start.