The current VO2Max (2021) test result
I'll first talk about the results and provide context later, and yes, I got better. I'm not getting younger, but my VO2Max actually went up by about 2 (from 48.1 in 2018 to 50.2). When evaluated against weight increase this is decent news because I did gain both fat and muscle (verified by DEXA scan), which means I gained aerobic capacity in absolute terms.
However, the most important number isn't actually VOM, but the anaerobic/lactate threshold (AT). This is the limit at which the body can clear lactate as fast as it is produced and is generally recognized as the endurance threshold (beyond which the effort is unsustainable). This went from 73% (148 bpm) in 2018 to 92% (173 bpm) of VOM. The aerobic threshold (AeT) also increased from 50% to 56%.
The 2018 Test Result
Taken in context, this is exciting news. After my first (miserable) marathon, I figured out that I needed to train slow, and I spent a ton of miles at maximum aerobic function (MAF) according to the Maffetone Method. Starting about a year ago I realized I was getting quite bored at this heart rate during long runs, so much that my joints would get sore prematurely (this has to do with running efficiency, like how you can run but not walk 6 mi). Coupled with the suspicion that MAF is generally only accurate for beginners, I've been bumping my training to progressively higher heart rates.
This test confirms my suspicion. In an ideal scenario, it appears that I can now clear lactate as fast as I produce it at ~170 bpm which is equivalent to ~7:50 min/mi. This would theoretically translate to about a 1:43 half marathon. During the Pasadena Half two weeks ago I ran a comfortable 1:43:12 in pretty close to ideal conditions. Considering anaerobic reserves and starting off quite slow b/c of race traffic, I might have even left a minute or two on the table, and I had none of the GI issues or DOMS (or indeed, any soreness at all) that usually accompany a hard race.
Resting Metabolic Rate (2021) Test
I had big hopes and dreams for low-carb running that were crushed during my first marathon, but I've since attributed it to the fact that I wasn't a good runner in 2018. Low carb running has its place; training without carbs, and especially depriving the body of exogenous sources of carbs up to 18 hours before long runs, really ramps up fat burning (since that's all that is available). Lactate is produced anaerobically through glucose fermentation and if you don't eat carbs then little is available to ferment. In layman's terms, fat burns cleaner than carbs. Without this training paradigm, I would not have seen such a big shift in lactate threshold.
Some other findings: a resting metabolic rate (RMR) test returned 2,333 kCal, which is 41% above baseline. This explains why my parents complain there's never any food left in the house.
Thanks to Athlete Lounge La - Pt-Rn Care, Inc. for the excellent testing services provided.