Thanks everyone for chiming in, appreciate it.
Can you run a 1:25 half OP? Going to be hard to cross train your way to a sub-3 if you don’t have the speed for it. I would start there. There aren’t really any shortcuts in the marathon. I would say most people going sub 3 need at least 50-60mpw to get there, if not more. I don’t think it’s as simple as running 30mpw & calculating how many bike miles make up the difference. Lifetime mileage matters. PBs matter. I’ve had good luck in open running races off of ~40-50mpw, in full triathlon training. But I came to triathlon with a running background & put together multiple builds topping out at 80-100+ mpw. It’s totally different for me now. I can get away with more of a swim/bike focus in training & still run well off of 50-60k/week. I think it’ll be hard to cut time & cut miles at the same time if base fitness isn’t where it needs to be. You’re going to need sub-19min 5k & 39-flat 10k speed at a minimum. You’ll probably need faster than that to have a chance on the lower mileage. My advice would be to not put pressure on yourself for a fall build. Hit the prerequisite times and find out how to balance the cross training with the training required to do that.
For the fall build I was hoping to break 3:30, so I apologize if the opening post was confusing. Long term goal BQ, which on paper will be 3:10 in a few years, but with how competitive Boston is, sub 3 is more likely to get me in the door.
Thanks for the benchmark recommendations. I havent done a stand alone 5/10k lately, however I’m coming in at <3:08 and <1:25 consistently for my track workouts (800/400’s respectively).
My PB for the half is 1:28
That 3:36, how much was very little? Like 10 mpw or 30? If you can do a 3:36 on very little training then general fitness gains will be enough to get you close to 3:00.
As a rule of thumb for running cross training you should maximize your running volume nearly to the point that doing any more will lead to overuse injuries. From there you can add in cross training.
I’m guessing that your fitness can still be improved generally before worrying about if HIIT or Z2 is more optimal for you. Doing a bit of everything is probably the safest bet.
Lastly weight is critically important for running. 2s/mile/lb is what they say. If biking helps you lose a few extra lbs then that’s obviously great.
It’s generally difficult to answer questions phrased as “if myself as an individual trains in this manner can I expect this very specific result?”. Without a complete training history it’s hard to guess, even with such a history it’s an educated guess.
My 3:36 PB was 8 years ago and was of very little training, I had done a 70.3 two months prior, but leading up to that marathon I was likely averaging <30 mpw, no cross training. I was clueless about HR and MAF back then but knowing what I know now, most of my runs were all “tempo” style runs.