Half Marathon DNF
Long post- I overthink everything
Background
M 37, 145lbs/66kg Picked up running in 2024 and after a quick 12 week block, ran a 1:32 HM on a tough course but great conditions, no real athletic background but moderately active. Decided to go in all sorts of different directions in 2025 before trying to focus on building aerobic capacity in late 2025. Mileage sat around 1k miles per year in both 2024 and 2025.
Training
Started off with vanilla NSM but did not do a 5k race or test so I was guessing (optimistically my fitness). My max heart rate was 191 from an all out sprint some time in 2024 and I didn't want to get there again so I didn't re-test. I also assumed my LTHR at 174 just from the way my body felt and LT1 at 141 also from feeling. I seemed to have no real issues with 4x4 workouts and 1min on/off fartleks on the treadmill at 6:00min/mi/3.44 min/k and was feeling confident so I started with the following structure with the treadmill well calibrated and set at 1 incline:
M 3x8min at 6:40min/mi (4:08min/km) 60s standing rest, 90-120s running around (8:50min/mi 5:28/km), 15min strength training, 15min sauna
T 1h EZ capped at LT1 (9min/mi 5:37min/km)
W 5x5min at 6:27min/mi (4min/km) 30-60s standing rest, 30-60s (8:50min/mi 5:28/km), 15min strength training, 15min sauna
Th 1h EZ capped at LT1 (9min/mi 5:37min/km)
F 8x3min at 6:19min/mi (3:55min/km) 30-60s standing rest, 30-60s (8:50min/mi 5:28/km), 15min strength training, 15min sauna
S 95min LR EZ capped at LT1 (9min/mi 5:37min/km)
Su 1h Strength training + 15min sauna
Over 21 weeks I mostly ended reps around 171-174 hr and progressed the length of the reps to be more half marathon specific but mid 1st rep my heart rate would usually climb into the high 160s. The peak week about 3 weeks out from the race looked like the following with max heart rate at the end of the reps noted, all speedwork done on treadmill and all easy work and long runs done outdoors, all sessions performed with around 40g carbs/h
M 3x12min at 6:40min/mi (4:08min/km) 60s standing rest, 90-120s running around (8:50min/mi 5:28/km) 1st rep 165 end, 2nd 171, 3rd 173
18min strength training, 15min sauna 179F, 7min cooldown bike
T 1h EZ + strides capped at LT1 129 AHR (8:18min/mi 5:09min/km)
W 4x6min, 1x6.5min at 6:27min/mi (4min/km) 30-60s standing rest, 30-60s (8:50min/mi 5:28/km), 1st rep 155, 2nd 164, 3rd 164, 4th 167 5th 173
15min strength training, 15min sauna, 7min cooldown bike
Th 1h EZ + strides capped at LT1 (8:33min/mi 5:19min/km) 128AHR
F 2x15min at 6:49min/mi (4:15min/km) 60s standing rest, 120s (8:50min/mi 5:28/km), 1st 163, 2nd 167
15min strength training, 15min sauna, 7min cooldown bike
S 140min LR EZ (8:28min/mi 5:16min/km) 128AHR
Su 1h Strength training + 15min sauna + 18min EZ treadmill (8:50min/mi 5:28/km)
Taper
Did a 10 day taper cutting back about 15-20% in the first 3 days while keeping intensity and following the HM taper of the book for the next week. For some reason, RHR during taper kept rising although the legs felt springy and the strides felt very good. Accessing speed was not an issue at all. Easy runs were run extra easy at around 122-125 AHR and sleep was on point at 7h45 avg with no alcohol or caffeine in the week leading up to the race.
Race
Started carb loading 2 days before the race and then increased the carbs the day before the race, hitting about 500g the day before. 5h30 sleep but expected. Had a morning coffee and another 50g carbs and hopped on an ebike to get to the start line.
The weather was about 50F at the start and I decided to take off my throwaway layer early because someone wanted it. Did some strides and drills and some breathing exercises but shivered a little. Was feeling pretty nervous at that point as could feel the humidity (85%) but thought it should be fine. Downed a caf gel 25min before start
The strategy was to post up with the 1:25 pacer and hang on for dear life- the 250ft of elevation was only in the first 5mi of the course so I thought if I could hang on with the pacer- the rest of the course should have been fine.
Mile 1: 6:35 123HR -18ft adrenaline rush but thought kept it controlled
Mile 2: 6:22 166HR -8ft no idea why the pacer was sending it around 6 flat on an uphill section, was struggling to keep up but thought will just hang on
Mile 3: 6:17 171HR -71ft rolling hills and thought would recover on the downhills
Mile 4: 6:26 177HR 7ft got to the 5k mat and saw the split was 19:45 and thought oh my I'm in trouble. At this point the guy next to me was like 'Yo I think the pacer is running hot'. Stared down at my wrist and heart rate was at 174 at the 5k mark and wouldn't go down no matter how hard I tried.
Mile 5: 6:37 180HR 61ft this was the biggest climb of the course, thought if I made it past this and tried to slow my heart rate down on the down hill then maybe I can salvage this
Mile 6: 6:38 182HR 28ft rolling hills and took my second gel- was refusing to go down and had to force myself to swallow. At this point the sun was fully up and I was not having a good time. My gait had also changed by this point and I was struggling to nose breathe.
Mile 7: 6:35 181HR -101ft HR refused to go down on the downhill and cadence collapsed- was starting to overstride and knew I was cooked
Mile 8: 6:52 182HR -15ft at this point I knew that if I didnt get my HR down I'd be in a world of pain so tried to walk for 15-30s to see if it normalized but ofc it did not
Mile 9: 8:05 179HR -32ft HR refused to go down despite trying to run/walk, left ankle started to feel a lot of pain, sun beating down, I had to make a decision at this point- either I have a very mediocre and extremely painful rest of the race with injury risk or I can just vibe and walk to where my friends and wife was at Mile 12.5 and decided to call it and just go back to the drawing board.
Mile 9-12.5 Walk of shame- took off my shoes and walked on the grass and just soaked in the vibes and reflected on the training block. I think maybe I was a touch aggressive on my paces and I was overconfident in this race and should have adjusted paces down due to the weather and definitely checked my hr more but this is what we got. Did not pace well (part of me blames the pacer) and have low racing IQ due to not racing often but I still have no regrets trying to shoot for a terrifying goal after having what I think was an amazing training block. While I had a few niggles here and there- nothing was screaming that my paces during the block were way too fast and some weeks really felt amazing. I was holding 50ish mpw on 7days a week for 7 weeks and the training felt great so I had to try. In the end, got a 2mi, 5k, 10k PR (12:36/19:45/40:17) and decided to wrap it up there. Not the smartest idea to PR these distances within a HM race but here we are.
Conclusion
Bad pacing, suboptimal weather, maybe too long rest periods during intervals and not enough race specific work and not enough race experience probably led to this outcome. Wouldn't call it entirely ego running but I really should have kept close tabs on my HR early in the race and this would have ended very differently. Still think that I am fitter than the race results suggest and maybe adjust the paces down a touch. I don't think I should also overreact to the race results and throw everything that I've built up out of the window just because of one bad day. I sulked for the rest of the day, spent time with friends and was still able to enjoy the rest of the weekend instead of being out for 2 weeks and unable to move so I like to think I made the right call risk/reward-wise. Happy to hear any feedback if you have made it this far. Also think some bad reports are necessary in this sub.