Difficulty 8/10 (depending on length/number of intervals)
Duration 50-80 minutes.
15 mins warm up
3-5 intervals of:
6-12 minutes @ 80-90% MHR
3 minutes easy to recover
Cool down
This is one of my favourite hard sessions, it really is a tough one when the intervals are quite long.
I have a power setting on my trainer, and I set it to around 220Watts and use 50x19 gearing.
If you do have a power setting you can make it extra tough by trying it at lower and lower cadences. I like to try it at 80-85 cadence.
Enjoy
(Where's the sweating smiley?)