Personally, I think your idea for double runs makes sense… If you’re unable to get a quality long run (3+hrs) in but are able to split it up into 2 ‘shorter’ runs then you should do it. It also sounds like your body is adapted to double runs without getting injured.
I’m no coach but I do a double run mid-week, hill rep, intervals etc. followed by an hour recovery Z1 later in the day. And once my Sunday long run goes above 3.5hrs I’ll tag an easy run later in the day. Personally, I do longer followed by shorter (3+2hrs). but that’s just me.
My reasoning is: I have a 7 month old at home, with very little support outside of me and my wife, although she’s supportive – me running for 4+ hours every Sunday does start to grate on her. This causes a lot of stress for everyone, I upcome non-present on my run and if I’m running late I pick up the pace which results in going into AnT territory. Like you, double runs seems to be the best way to increase weekly distance.
For your adventure runs – it sounds like you’re getting in some good weekly kms and it doesn’t sound like you’re going to be able to increase that. So, I’d suggest sprinkling in a few simulation weekends closer to the adventure run, for instance, 3 days of 3hrs etc. but that depends on your adventure race distance.
A way I sneak mileage in is to incorporate the family into a planned run, for instance, I’ll pick a family walk/activity that’s 2-3hr run from home. They’ll drive and I’ll run – we’ll walk for an hour or so and I’ll then run back. It seems to work well.
I read somewhere about diminishing results after 3hrs so by splitting a long run up – will allow your body to replenish glucose levels etc. – although I’m not 100% on that and I don’t think I’ve ever seen that mentioned in UA literature?!
The way I see it, we need our partners to be onside if we want longevity in our (sometimes selfish) pursuit in endurance sports. Realistically, the adaption won’t be much less. Your body will still have the cumulative effect of all the mileage over the week.
