Boston to Grandma's was the second time I've tried two marathons in approximately 2 months; Chicago to CIM was the first.
I learned from that first attempt, and changed up some things for the second try. And now, for future reference for myself and anyone else that may be interested, here's what I've learned.
But first, it's worth noting that we're all experiments of one, both in running generally, and in multiple marathoning. Additionally, I recover relatively slowly compared to others. Thus, my lessons learned apply to me, but may or may not apply to others. When I write "you" here, it's really directed primarily at myself. With that disclaimer in place, hopefully this is still of use to others.
When I refer to "back-to-back" marathons I mean two marathons, both raced all out, within approximately 7-10 weeks. A very specific pattern that differs both from fully raced marathons that are either closer or further apart, and from targeting a second race after dropping out of or jogging in the first.
Two all-out marathons within a short period of time is very simple to structure (though not easy to pull off). You just rest and hope to recycle your fitness from the first race. On the other end of the spectrum, two marathons with 3 months or more is doable if not ideal. You have enough time to rest and get a solid training cycle in. And if you dropped out of the first marathon (assuming you dropped out at mile 20 or before), you don't have to worry about recovery from a full marathon, so it's just a matter of extending your training cycle.
[to that point - I really believe that if a time goal is of the utmost importance to you, be it a Boston qualifier or a Olympic Trials qualifier, it's far better to drop out of your first marathon at some point before mile 20 if it's obvious at that point that you will miss your goal. Dropping out of a marathon is obviously very tough mentally, but will set up you up much better for a second try in the next few months.]
Two months between two all-out marathons is tricky. It's enough time to lose fitness, and not enough time to fully recover. You have to balance rebuilding fitness for the second race with recovering from the first, and you don't have enough time to do either well, let alone both simultaneously.
So, it's tricky. Here are my tricks.
There is a right time to decide you want to race a second marathon. And that time is at least 10 days after finishing the first race. If you start the first race counting on having a second chance to run your fastest in a few weeks, it will be very hard to commit totally to marathon #1 and leave it all out there. As for immediately after the marathon... emotions are high, and can interfere with one's judgment. It also takes a good week or two to assess how you are recovering from the first race.
This time, though I started thinking about doing another marathon a few days after Boston, I didn't commit to Grandma's until 3 weeks post-Boston, after I had completed a workout of 2x4 miles at marathon pace. Though that workout didn't go great - I was still very tired from Boston, it went well enough to confirm that I was recovering reasonably quickly and that running Grandma's well (for a distinct definition of "well" - more on that below) was possible.
I do think that there's nothing wrong with entering a first marathon with the hopes of running a second marathon later for fun without a time goal - choosing something like Boston or New York or Big Sur, where the second race is about the experience and not for time. But that's not the scenario I'm discussing here.
Management of expectations before the race is key.
The first time I tried back-to-back marathons, I had hopes that I would be able to improve on my fitness from the first marathon, and run even faster in the second. CIM proved me wrong. On a perfect weather day and a very fast course, I finished 2 minutes slower than my Chicago time, despite running a smart, well-paced race. I didn't have the same fitness I had at Chicago, and I also hadn't recovered from Chicago.
Thus, when I doubled back to Grandma's, I also dialed back my hopes. I believe I was in 3 hour shape at the end of my Boston cycle (assuming a very fast course and perfect weather - neither of which applied to Boston) and trained accordingly. For Grandmas, I pulled back to train as if I was in 3:05 shape -basically a 5 minute penalty for the second marathon.
More important than the time, though, was having non-time goals. It's a sports-psychology truism that most of us don't perform that well if we're exclusively focused on a specific end goal, like a time or placing. Process-oriented is better than goal-oriented, blah blah blah.
That rule applies double when doubling back. Stated another way: revenge races don't work. If you are going to tack a second marathon onto your training cycle, you need to have additional reasons to run the second race besides wanting to improve on your first time. Something so that the race will still have been worth it if you don't run faster the second time around. Because it's highly unlikely that you'll run faster the second time, and chasing an unrealistic goal will lead to poor training decisions at a point where you have absolutely no margin for error.
Put another way: if your only purpose for doubling back to a second marathon is to beat your time from the first, don't waste your time and your body. Rest and recover, so you can take your best shot a few months later.
Don't Rush the Recovery.
One of the biggest mistakes that I've seen is that people rush back into training for #2. It's an awful idea. Yes, I know that you have another marathon coming up in less than 10 weeks, and it's hard not to panic when you're not running at all in the first week after the first marathon. But recovering from the first marathon must be your top priority if you want to run marathon two well. Or heck, run it at all - it seems like the majority of those I know who try to double back never make it to marathon #2, felled by the fatal error of jumping right back into marathon training after the first race.
You are not going to improve your fitness between the two marathons, so don't bother. Make sure you recover as well and as quickly as you can from the first, with your second priority being maintaining your fitness.
This is another reason to slow down your target marathon pace for the second race when you ease back into training (after recovery). I did this for Grandma's, slowing my goal pace from 6:50 to 7:00. Doing this worked well because 1) it was a better match for my current post-Boston fitness (one should always train to current fitness, not what you had 6 weeks ago) and 2) slowing stuff down helped me recover from Boston even as I tried to get ready for Grandma's.
Manage your expectations during the race.
The first time I tried doubling back, I assumed my body would feel the same way during the second race. I learned differently. The truth is that it takes longer to truly recover from a marathon than it does to feel like you're recovered. There are reserves that you don't realize you're lacking until you reach for them - and they're not there.
This is easiest to explain with an analogy. In the first hours and days after a marathon, most of us are pretty sore and tired. Then we start feeling better. And then you go for a run, and realize that you're not recovered yet.
Later, after you've been doing easy runs and everything feels fine, you hop into your first workout back. And everything feels fine, and then all the sudden it doesn't. And you realize that you're not recovered yet.
Running a second marathon follows a similar pattern. Everything feels fine until it starts getting hard, at which point you realize that your energy pantry hasn't been fully restocked. It's a strange feeling - akin to low tire pressure - that I've only felt twice - when I doubled back to CIM in 2016 and to Grandma's in 2018. And no, it's not bonking, or cramping, or blowing up due to pacing errors - I've done all of those and know how they feel - this is different.
Conservative and steady pacing is key in the marathon, but even more when doubling back. Because you really don't have the reserves that you normally do.
Timing between marathons.
Every week between the two races matters. There are some people who race very well at shorter distances 3-4 weeks after their goal marathon. If that's you, then this probably doesn't apply to you. But....for the rest of us, you need to have enough time to recover from the first marathon and also to restore your fitness.
That generally means at least 8-9 weeks between races, with more time being better. If you have less time then that, than I think it's better to run the second race 2-4 weeks after the first, and just rest between the two.
5-7 weeks is the worst choice in terms of spacing marathons - it's just enough to lose fitness between the two, but not enough time to either recover from the first or train for the second.
How I trained between Boston and Grandma's.
In case it's helpful, here's a quick summary of what my training looked for the 9 weeks between the two. For comparison, my normal marathon training volume is about 60-65 miles on land and another 15-20 "miles" pool-running.
Week 1: Boston Marathon on Monday - just pool-running and a bit of swimming and junk food the rest of the week. Only priority is recovery. Thinking about doing Grandma's Marathon, but not committing.
Week 2: 44 miles running, all easy, with the longest run being 11.5 miles. Also a tiny bit of pool-running and swimming. Chat with coach - he is on board with Grandma's Marathon if I feel like I'm recovering well.
Week 3: 56 miles running and 16 "miles" pool-running. Did some short hill strides on Tuesday, a controlled 3200,1600 at tempo pace on Friday, and then 2x4 miles at marathon pace on Sunday as part of a 14 mile long run. Goal marathon pace is 7:00, not the 6:50 it was for Boston. After the 2x4 goes decently, decide that I am running Grandma's Marathon.
Week 4: 66 miles running, 18 "miles" pool-running. Track intervals on Tuesday, 4 mile tempo on Friday, and 18 mile long run with last 6 miles at goal marathon pace.
Week 5: 64 miles running, 18 "miles" pool-running. Track intervals on Tuesday, broken tempo of 3200, 1600 on Friday, and then a 16 mile long run on Sunday including 2x5 miles at goal marathon pace.
Week 6: 65 miles running, 19 "miles" pool-running. Track intervals on Tuesday, 5K tempo (was supposed to be 8K but I bailed) on Friday, and 21 mile long run on Sunday with last 7 miles at goal marathon pace. Start tapering. Again.
Week 7: 46 miles running, 17 "miles" pool-running. Track intervals on Tuesday, 5K race on Saturday, 14 mile long run on Sunday.
Week 8: 50 miles running, 12 "miles" pool-running. Track intervals on Tuesday, 5K tempo on Friday, 10 mile long run on Sunday.
Week 9: Race week. 16 miles running and 6 "miles" pool-running pre-race; Grandma's Marathon on Saturday.