Cadence and a training session goals

Each session has its own focus, targets and drills.
Very often one is asked go keep 85-95 rpm or above, unless performing other drills.
What is the impact of one getting as low as 70 or even 65 just to manage to get the target power in relation to the productivity of a session where it is advised to have a cadence of 90 and higher?

(Just finished and over under threshold session in which as the workout progressed I could get the numbers but had to resort to lower gears/ lower cadence for it).

Not great for your knees I would imagine - I average 95-100 rpm on the trainer and about 80-90 on the road (90 for endurance and about 80-85 while TT racing). I also find VO2 efforts easier at 110rpm when operating at 120% FTP - so variety is ok and everyone is different but getting bogged down below 70 doesn’t sound great for joint health AND if you use ERG mode on a smart trainer then you are risking the spiral of death which occurs when cadence drops to low :grimacing: