Most folks aren't really familiar with what training for competitive cycling (or structured training in general) looks like.
There are large, month-scale blocks where you're simply building aerobic capacity by cycling at low-ish intensity. Heart rate is somewhere between 115 and 145 for me personally during these efforts. 15 hour (or more!) weeks are not uncommon.
Nils van der Poel was doing something like 6-hour blocks of zone 2 during his base season as an Olympic speed skater.
When outdoor riding is available, it's preferable, but indoor trainer sessions are basically always more time efficient for a given training load. You make consistent power, there aren't street lights or flat tires. If you run out of carb mix you go to the kitchen and fetch more. In winter, it's the only reasonable option. Going for a ride in -15C and salt slush is fine for a commute (crazy, I know), but doing it for 15 hours a week, probably in the dark, is not reasonable. Indoor is the only practical option to get this training load in winter.
Most people just watch TV or use Zwift (social riding simulator) during these blocks. I'm not much of a TV guy, and to be honest, I find a good technical problem to be great distraction from the drudgery of Zone 2.
Note for OP: I've actually considered using a split keyboard in a very similar way to this. I run aero bars on my bikes for ultra-distance events, and I have them on the trainer right now. At some point I would like to mount a split keyboard to the aero extensions themselves - this would take all the load off the wrists. It is also possible to use the aero bar armrests without the extensions and to be able to type this way. If I end up prototyping this I will shoot you an email.
The reason we know Niels van der Poel's training in such detail is because he wrote a manifesto about it, "How to Skate a 10k", when he retired (after winning gold and setting the WR). He did his base aerobic phase primarily on bicycle, writing:
> My target developed during the summer of 2021 to reach 33h of cycling weekly. I would aim
to do three 7h bike rides and two 6h rides. If I would’ve been able to run, which I wasn’t due
to injury, I would have lowered the hours a little and settled for 25h weekly (or approx. 30h if
I would’ve combined running and cycling).
33h at 240 watts, about 28k calories/week!
It is a fascinating read for anyone interested in endurance sports, highly recommended: https://www.howtoskate.se/
I raced at an elite amateur level for about a decade and I never really saw the purpose of those huge zone 2 training blocks. Almost no races were more than four hours long and most were in the one to three hour range. It felt like there was a lot of cargo culting of european pros who had very different requirements given the far longer races they were doing over there. Unless you are an aspiring pro or willing to sacrifice your life to cycling, I tend to think those long z2 blocks are a waste of time. I loved riding, but I found zone 2 rides to be pure drudgery if done more than a few times a month.
Hard intervals a few days a week with one or two long rides every week or two are more than enough to race at the cat 1 level (assuming above average VO2 max and if you don't have that no amount of z2 is going to make you competitive anyway). At my peak, my threshold was around 5 W/Kg, ~10 W/Kg for 1 minute and 20+ W/Kg for 5 seconds. My biggest week of training was less than 20 hours and I averaged around 10 hours per week for the years I was racing.
Plans I see for time crunched athletes tend to do more Z3 plus higher zone intervals, so I think your take is valid. I train for XC MTB (my A-race is 60miles ish) and ultra distance, so maybe the Z2 work is more important for me.
However, this is all beside the point - whether it makes sense or not, there are a lot of folks doing polarized plans that involve a lot of Z2, so the desire to be able to type while on the trainer isn't unreasonable.
Most folks aren't really familiar with what training for competitive cycling (or structured training in general) looks like.
There are large, month-scale blocks where you're simply building aerobic capacity by cycling at low-ish intensity. Heart rate is somewhere between 115 and 145 for me personally during these efforts. 15 hour (or more!) weeks are not uncommon.
Nils van der Poel was doing something like 6-hour blocks of zone 2 during his base season as an Olympic speed skater.
When outdoor riding is available, it's preferable, but indoor trainer sessions are basically always more time efficient for a given training load. You make consistent power, there aren't street lights or flat tires. If you run out of carb mix you go to the kitchen and fetch more. In winter, it's the only reasonable option. Going for a ride in -15C and salt slush is fine for a commute (crazy, I know), but doing it for 15 hours a week, probably in the dark, is not reasonable. Indoor is the only practical option to get this training load in winter.
Most people just watch TV or use Zwift (social riding simulator) during these blocks. I'm not much of a TV guy, and to be honest, I find a good technical problem to be great distraction from the drudgery of Zone 2.
Note for OP: I've actually considered using a split keyboard in a very similar way to this. I run aero bars on my bikes for ultra-distance events, and I have them on the trainer right now. At some point I would like to mount a split keyboard to the aero extensions themselves - this would take all the load off the wrists. It is also possible to use the aero bar armrests without the extensions and to be able to type this way. If I end up prototyping this I will shoot you an email.