Sounds like quite a few people were interested in that last post on MAF training... I received some messages from people who were trying it and had that experience of OMG This is so slow is it really beneficial to go this slow?? I get that. Hang in there. It does get better but it will get better faster if you do it often and are diligent/disciplined.
One thing I thought I'd also mention is that MAF training works on the bike too! I am lucky in that I have a ride option that is pretty much out my door that goes quite a ways with very few interruptions... mostly flat road, windy much of the time, but not a lot of lights and/or turns to interrupt me... so I go out and ride that most of the time. Boring, maybe, but it gets the job done. I can essentially do a trainer workout outside on this route. :) Anyway, you need a route like this for a MAF type bike workout b/c the goal is to ride at a very steady effort, and that's hard to do when you're stopping at a light or a stop sign every mile.... or twisting and turning through neighborhoods... or going up and down steep hills...
Anyway, MAF is the same thing on a bike. Know your range, maybe it's a little lower on the bike, maybe not. Personally, I use the same HR range for bike and run. When I first started MAF training on my bike 2 years ago I had to back off and soft pedal to keep my HR <150. Especially up a hill or into a headwind. It didn't take too long though until I felt like I was actually riding and my HR would stay where I wanted it. Then it got to the point where it was really all about staying >140 vs staying <150. Like, I had to work fairly hard and stay focused to keep HR >140. No sight seeing!! No soft pedaling! Pedal consistently all the time so your HR doesn't drop. Not that hard for an hour or so but go do that for 5 hours every week and guess what? You get strong on the bike.
I find group rides are the opposite of MAF training. Groups tend to go super slow/easy then HAMMER then back to super slow/easy then HAMMER again. Fine to train like that if you're a cyclist but if you're a long distance triathlete, well, this is the opposite of the type of fitness we want to gain.
My experience coaching women over the years is that many have a hard time getting HR up on the bike. This makes sense of we think about what makes heart beat harder? Muscles demanding oxygen... so muscles working harder = increased demand for oxygen = heart beats faster trying to supply it. So if a woman- especially a woman who is new to cycling- isn't as naturally muscularly built, she may not be recruiting strong muscles for pedaling that require a ton of oxygen. SO, no need for heart to beat faster. But that also means she's not riding very fast and that's what we're trying to fix... so for some women MAF training on the bike is opposite of MAF training on the run b/c it forces them to push harder to keep HR up vs backing off to keep HR low. Not all women have this issue of course. Some women (me included) are, for whatever reason, more muscularly built and in my experience these women tend to have to back off to keep HR low... at least until they get more fit. So it's pretty individualized.
If you have a power meter then you can track your MAF progress similarly to the way you would with pace on the run. So say you're just starting out a new cycling base period and you go out and avg 146 HR on the bike for 2 hours and end up pushing 150 watts to do that. Then next time you go do the same ride, same HR, but power is 154W. Then next time it's 160W. So that HR/power ratio is one we can watch to proves how you're improving. Just know that even if you don't have a power meter, ride like that and you will still improve even if you can't track those numbers. The first year I did this type of training I did not have a power meter but I knew I was making big improvements primarily b/c I ended up feeling like a bulletproof machine on the bike (even at the end of 5 hours) and my rides were faster with same HR avg.
Part of the reason we do this type of MAF training (both bike and run) is so we become more metabolically efficient- preferentially burning fat for fuel vs ripping through our glycogen stores. For athletes who are racing shorter distance races this matters A LOT LESS. A key reason people don't race faster at short races is that they are fitness constrained. They don't train hard enough. A reason people don't finish Ironmans stronger is that they are fuel constrained. They don't train smart enough. Alan Couzens wrote a really smart blog about this a couple years ago.
One last thing about the benefits of MAF training... your run pace at MAF is your run pace at MAF, regardless of whether or not you biked 100 miles first or not. Dehydration and heat can factor in of course, but I will tell you, I live in Hawaii so I train in heat much of the time... once you're adapted and fit, if you stay at least mostly hydrated, you'll be able to run off the bike the exact same pace you would run after waking up in the morning and having a cup of coffee... For an Ironman athlete, this is a beautiful thing! Of course, to maintain this pace for a full 26.2 miles one needs to have enough muscular endurance to not break down in that way. Most Ironman athletes aren't struggling with heart rates that are too high at the ends of their marathons... they're struggling with legs muscles that are rebelling the distance. So at some point once we're cardiovascularly fit enough, we move on and start really focusing on training that muscular endurance... But that's another topic for another time. :)