Turbo Trainer Advice

Right.

Dammit's borrowed bits attached to bike. Trainerroad subscription purchased (it looks ACE, btw). 8 minute test run for first time.

Apparently I'm only outputting 79 watts when my HR is at 171!! I think I haven't set it up properly, I don't understand the target power at all. It seems to be asking me to generate 100w in the beginning warm-up stage, but if I'm in the big ring and a middleish cog, spinning at 80-90rpm, that's supposedly 80w or thereabout. I could spin faster to get closer to the target, but that's going to spoil my tempo. I could gear into a smaller cog, but I'm already in a fairly high gear as it is. Um.

Also, I haven't got a garden, any DIY, or a sex life, so yes, this is how I spend my evenings now. Don't judge me, alright.

Those numbers don't seem right. Have you selected your turbo trainer's profile in the pull down menu? The software needs to know your kit so it can use the correct power curve so it can generate virtual power data.