I have some coaches that are pretty hot on this topic.
The theory (and by that I mean scientific theory not guesswork) is that zone 2 is where you build aerobic endurance. In this zone your body uses a large chunk of fat for fuel as opposed to sugar. When people talk about building a base they are primarily talking about this zone.
You do not have a single ‘fitness’. You have various fitness within your HR range (which is probably why sprinters and marathon runners can’t do the other discipline and win - they are fit for purpose not simply fit for everything). Your fitness in your Zone 2 sounds poor, as you are slow within that zone BUT running within that zone is absolutely correct and yes, you will be slow at first. Once you start to train with that HR as a limiter you will start to get faster within that zone. Being faster in zone 2 is great, because you are starting from a faster platform when you head into zones 3 and 4.
As an example, I used to run 5:15 per km within my Zone 2. Continued training over a couple of years in that zone puts me now at 4:35 per km within that zone. I now have a much better platform from which to push higher HR’s and pace during events. My body uses a lot more fat at higher speeds than it used to because I have trained my zone 2 speed to be a lot higher than it was before.
I coach a few people who all have the same issue. They say that Zone 2 is too slow. It’s not. They are just not trained very well at that zone. They limit their HR and after weeks or months they start to see a significant shift.
I would say … ensure your zones are right (get a proper lactate test) and then train slow if that is what you need to do to sty within that Zone 2. Obviously Zone 2 is just part of your training program and likely a large part in the off season.
" … If I go any slower it will feel like I’m not gaining any benefit from the run at all. …" Wait until that slower starts to get faster at the same HR. Having a consistent course to rain on helps to establish the improvements as you will see your pace and times start to come down.
There is also another benefit of training in Zone 2. You develop more slowtwitch muscles fibres. Fast muscles fibres are unable to deal with lactate, slow twitch muscles fibres are supposed to be able to use lactate as fuel. In a race, if you have developed your ST fibres, by running in Zone 2, more of the lactate all be a benefit than a hinderance compared to what you had before when it comes to race day.
I am not a scientist, this is just what I have ‘learned’ during my time being coached and reading articles by respected coaches and endurance bods. So … it’s second hand info but it has helped me tremendously and I have seen huge results from a lot of people who have used it.
Hope that helps.
