stupid to try to cram for Boston?

Definitely do another solid long run. I would push the pace at the end, but don't be reckless. Aim for medium-hard. One way of thinking about these runs is that when you're really well trained, you stop responding to small and medium stimuli, so only monster workouts can push you higher. When you're not well trained, the approach is straightforward: you want to keep getting a high frequency of moderate stimuli. So do a moderately hard long run, and there's no question you'll be recovered in time for Boston. A three week taper is excessive when you're undertrained, and even with a traditional three-week taper, you still have room to gain fitness with solid workouts in the 10-14 day range.

Thanks this is helpful. I think you are right that 3 weeks is probably excessive since I'm undertrained and don't feel particularly beat up. I appreciate it.

I disagree, you might have trouble recovering in time...I would save it for race day.

Wow, we are pretty much the exact same person. 41yo, 70 mpw with 80-90 peaks during buildup. Generally, did two workouts a week (track and tempo) plus a weekend long year round.

This last build up, I did a short 8-week plan based on Daniels with a slightly smaller base (55-60mpw). Instead of two workouts plus a weekend long, I was doing two long workouts, one with short intervals mixed in, and the other with MP or long threshold segments. Basically ended up with two 12-18 mile runs per week, both with a lot of quality mixed in. Everything else was easy. The whole buildup, my body felt great (3 days between hard efforts 👍), and the fact I was crushing the workouts really boosted my confidence. Late peak at 83 miles just 3 weeks out. I did a 24-mile 3-hour easy run that week, and a 19-miler with two 6MP segments just two weeks out. The proximity of that last workout kinda scared me going in, but it was in the schedule, and I felt great after.

Landed a meh day for the marathon two weeks ago (65°F and drizzle) and still PR'd by 2 minutes (2:55). Will definitely try this buildup again as I think there's definitely some meat on the bone (I'm a big guy and thrive in cooler temps).

TL;DR - Don't sweat the long run 3 weeks out! And don't be afraid to follow it with a good workout 2 weeks out. YMMV of course 😎

No, it typically takes ~4 weeks to see fitness gains from a long run. Doing something marathon specific is a good idea, but I'd put the focus on MP miles. Two weeks out gives you some recovery time to work with, but it's cutting it a bit close for a straight long tempo. Maybe 2 x 4-6mi or 3-4 x 3mi, depending on how fit you feel.

With a warm-up, jogging in between reps and cool-down, the entire workout might ultimately get up toward 20 miles, so in practice there may not be a huge difference, but I'd put the focus on the MP segments rather than just covering the miles.

(In any case, you're probably better off than me. After Covid last fall, I only felt like I got back to normal running in August, I only made it to 70+ mpw once, and now I'm tapering already for an A-goal 10K race this weekend. Boston is going to be a "whatever happens, happens, and whatever happens might be really bad" race for me, unfortunately.)

colder and wiser wrote:

No, it typically takes ~4 weeks to see fitness gains from a long run.

This isn't really correct. It's one of those Runners World rules of thumb that's premised on the idea that long runs are slow and intended mostly to increase capillarization (which does take a long time, but which is not really an adaptation that's relevant to experienced runners because we're already mostly maxed out in that department). The mistake is assuming that there's one kind of long run with only one purpose. The kind of long run the OP and I are talking about is a faster, more marathon specific workout. While there isn't a consensus about what adaptations we're seeking from that kind of a workout (many would argue that it's better substrate utilization, I disagree and would suggest it's more neuromuscular and psychological), those are definitely adaptations you can realize in 14 days. You seem to acknowledge as much in suggesting that the OP do an MP workout that's not a long run. That's a fine approach, but it's honestly not that different from doing a fast finish long run, especially for a non-elite.

Also, even if it really were impossible to gain additional fitness from a long run two weeks out (which it isn't), not all workouts are about increasing fitness. Many workouts are about maintaining fitness, which degrades very quickly without regular stimuli. Part of the art of periodization is figuring out how to provide enough of a dose of training to keep what you've built while at the same time either (1) building some other attribute or (2) shedding accumulated fatigue so that you can summon a peak performance.

Too late for the 20+ miler even with the quality built in.

So, take it for what it's worth, and I'll admit I'm pushing it a bit, but I'm doing a half marathon race this Saturday at my GMP with about 20 min up and 20 min down to not exceed 18 miles total as my final big effort figuring 16 days is enough to recover from that. After that, less is more.

I'd do a run like that where you do 16-18 total miles with some GMP/uptempo effort in there. Another idea would be 4x2T with 4 up and 4 down on either side.

But as far as 20 milers go, last weekend was the latest to do that IMHO.