Ironman Training Diary - August 25, 2026: Four Miles in Dublin
← Click here to read this diary from the beginningHad an OK run today. 4 miles in moderate heat and humidity. Approximately 2 miles in I felt a pretty strange sensation in my right knee in that it started spasming and buckling. This continued for maybe 2 minutes before fading away. The following morning I woke up with a similar twitch in my right achilles which like the knee issue went away after a few minutes. Not sure what to make of it. Fortunately the next workout involves swimming and an 8 mile ride so I’ll stay largely off my feet for 36 hours.
The run was another very slow paced activity with the goal of keeping the HR under 145. I largely succeeded at that but wow is this a boring pace. Along the way I listened to Lex Fridman’s interview with Khabib Nurmagomedov. Pretty inspiring stuff, and a great example of what can happen when you combine extreme discipline with a desire to win (or in Khabib’s case, to not lose).
🤖 Apollo (AI) analysis
Today’s run — 4.00 mi, 62.2 min, 10:40 AM start
Observed facts:
| Mile | Pace | Avg HR | Max HR | Cadence |
|---|---|---|---|---|
| 1 | 15:02 | 128 | 140 | 156 |
| 2 | 15:35 | 140 | 148 | 152 |
| 3 | 16:04 | 145 | 151 | 146 |
| 4 | 15:32 | 144 | 148 | 148 |
| Total | 15:34 avg | 140 | 151 | — |
HR distribution: 13.4 min in Z2, 47.4 min in Z3, zero in Z4/Z5. Fastest mile within the run: 14:55.
What this run says
1. This is the aerobic-control profile you want in BASE-1, extended to a new distance. Your last comparable easy effort (Aug 18) held ~15:40 pace at ~137 avg HR for 2.76 mi. Today you held essentially the same intensity — 15:34 at 140 — for 4.0 miles. Compare Saturday (Aug 23): 16:10 pace at 152 avg HR over 5.72 mi. Today you ran faster than Saturday at 12 bpm lower average heart rate. I will not call that a fitness gain — the confounders are real: Saturday was 1.7 mi longer, started at 12:08 PM (likely hotter), and came after a different training week. What I can say: today is consistent with the pattern that your controlled-easy runs are getting longer without the HR ceiling rising, which is exactly the adaptation base phase is for. A controlled benchmark (same route, same time of day, same distance, two weeks apart) remains the only way to confirm it.
2. The drift is visible but bounded. HR climbed 128 → 145 across miles 1–3 while pace slipped 62 seconds and cadence fell 156 → 146 — then mile 4 stabilized: pace recovered 32 seconds, HR held flat at 144. That mile-4 recovery matters more than the mile-3 sag. Genuine aerobic-limit decoupling doesn’t reverse in the final mile; late-morning heat accumulation plus a mid-run lull does. Confounders I can’t rule out from the data: no temperature stream on this device, and I can’t see terrain shifts (elevation shows ~118 m of corrected gain, which for your flat Dublin routes I distrust on principle — likely partly altimeter/correction noise).
3. The morning context lined up well. RHR this morning was 58 — the lowest in the recent data, down from 64 the previous two days — on 8.3 h of sleep. Whatever else is true, you did not run this on a suppressed-recovery morning; that’s the opposite of the RED-S signature I told you to watch for. And note the fueling experiment you accidentally ran: the 42-g-fat breakfast sat 2 h 10 min before this run. For a Z2–Z3 effort that gap was evidently sufficient — no pace collapse, no mile-1 sluggishness beyond a normal warm-up profile. Do not generalize that to quality sessions; the 2–3 h guidance stands for anything with intervals.
4. One flag: cadence. 156 → 146 across the run is a meaningful decay, and low absolute cadence at slow paces usually means longer ground-contact and more vertical oscillation per meter — cheap injury-risk currency in a build phase. Confidence that this matters at your current volume: moderate. Worth watching whether the fade repeats on longer runs; if it does, a metronome mile or two mid-run is the standard fix.
Recap: Today: 4.0 mi @ 15:34, avg HR 140, all sub-Z4 — same easy intensity as your Aug 18 run carried 45% farther, with bounded drift that self-corrected in mile 4, run on your best RHR morning (58) of the stretch. Watch the cadence fade; confirm the apparent aerobic progress with a controlled repeat rather than assuming it.