Chasing 12:03 — 25 Years Later
Way back in high school, our PE teacher had a simple grading rule for the running unit: run two miles in under twelve minutes to earn an A. I crossed the line in 12:03, just three seconds too slow, finishing with three classmates ahead of me and a big gap to the rest of the pack. The teacher grouped the four of us together as the “A group,” and I remember feeling both lucky and completely exhausted.
Now, more than twenty-five years later, I’ve set myself a new goal: to train, prepare, and finally beat that 12:03 mark. This time, it’s not for a grade, but rather it’s for the challenge, the process, and the satisfaction of seeing how much smarter and stronger training can be the second time around.
I recently completed a hilly 10 km race in 44:43 (4:28 min/km) and have an upcoming 8 km event that I ran last year in 34:25 (4:18 min/km). Using a simple linear estimate, if I can run 5–10 seconds per kilometre faster for every 2 km drop in distance, then my targets would be roughly 4:10 min/km for 6 km and 4:05 min/km for 4 km.
Rather than chasing pace alone, my training focuses on improving my lactate threshold, the effort level where speed and endurance meet. By raising the pace I can sustain just below and slightly above this threshold, I believe that is my best training option for turning that old 12:03 benchmark into something I can finally beat.
6-Week LT2 Development Plan
Objective: Raise LT2 pace (~4:20 /km) toward 4:05 /km to support a 3.2 KM (less than 12 min) goal by January 7 2026.
Structure: Two quality sessions per week (Sunday & Thursday).
Emphasis: Aerobic efficiency, threshold durability, and recovery balance.
Target Zones
| Zone | HR Range (BPM) | Pace Range (min / km) | Description |
|---|---|---|---|
| Easy / Endurance | ≤ 121 | 5:30 – 6:00 | Aerobic base, recovery, capillarization. |
| Over–Under (Below) | 139 – 144 | 4:40 – 4:30 | Controlled aerobic effort near LT2. |
| Over–Under (Above) | 147 – 155 | 4:20 – 4:10 | Mildly above LT2; improves lactate clearance. |
| Threshold (LT2) | 146 – 152 | 4:20 – 4:05 | Core development zone for raising LT2 pace. |
| VO₂ Intervals (250 m) | > 155 | 3:35 – 3:25 | Speed maintenance, neuromuscular turnover. |
Weekly Layout (Monday – Sunday)
| Day | Session | Purpose |
|---|---|---|
| Monday | Rest | Full recovery; consolidate adaptations. |
| Tuesday | Endurance Run (LT1 below) 6–8 KM | Maintain aerobic base with low fatigue. |
| Wednesday | Mobility + Strength (30 min) | Core stability, single-leg control, hip strength. |
| Thursday | Threshold Intervals (LT2 above) — start 3 × 2 KM (2 min jog recoveries); progress to 3 × 2.5 KM by Week 6. | Primary LT2 stimulus; accumulate 25–35 min near threshold. |
| Friday | Recovery Jog (LT1 below) 5 KM walk if needed | Promote blood flow and recovery. |
| Saturday | Endurance Progression (LT1 below) 7–9 KM; finish last 2 KM steady (below LT2) | Extend aerobic capacity; steady pacing under mild fatigue. |
| Sunday | Over–Under Run 7–8 KM — alternate 5 min (LT2 below) / 2 min (LT2 above) | Controlled lactate exposure; bridges aerobic and threshold systems. |
6-Week Progression Focus
| Phase | Weeks | Focus | LT2 Time Target |
|---|---|---|---|
| 1 – 2 | Base Control | Learn HR discipline; manage drift | 20–25 min @ LT2 |
| 3 – 4 | Threshold Expansion | Extend duration; reinforce pace control | 25–30 min @ LT2 |
| 5 – 6 | Tolerance + Sharpening | Final reps touch LT2 above for 2–3 min | 30–36 min @ LT2 |
Notes
- Sunday & Thursday: Key quality days — manage recovery between.
- Tuesday & Saturday: Supportive aerobic days, stay relaxed.
- Optional VO₂ tune-up: Every 3rd week replace Thursday session with 8 × 250 m (LT2 above → VO₂) 90 s rest.
- Monitor HR trends: If resting HR ↑ > 5 BPM for 2 days, skip next hard session.
- Re-test LT2 pace late December; adjust zones before sharpening phase.
Week 2: Saturday, November 8
Today’s training objective was to complete a 7-9 KM run below LT1 under mild fatigue and that is extactly how the training went. 7 km distance, heart rate ≤ 121 BPM with an average pace of 10.8 km/h. The dips in heart rate are due to waiting at traffice lights. Notice how gradual the heart rate increases once I started to run again.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Normally when I get close to 120 BPM I have to slow the pace a lot to bring the heart rate down, however today, I just had to slow the pace slightly to bring down heart rate. I attribute this improved control to proper execution of last Thursday’s LT2 effort, which had just the right amount of stress to encourage adaption.
I skipped increasing the pace over the last 2 km because the LT1 effort felt like enough stress. Looking forward to tomorrow’s over-under effort!
Week 2: Sunday, November 9
Today’s over-under run went well. Easy warm-up for 3 km then build pace until target heart rate reached and then hold for 5 minutes then increase for 2 minutes over, repeated for 30 minutes. The focus was heart rate range keeping the under between 140-144 BPM and the overs between 146-154 BPM. The pace felt great during the 2-minutes over. As I moved back to the under range the breathing was very deep for several minutes; getting more comfortable tolerating the deep breathing.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 2: Summary
The Acute Training Load (ATL) has increased too quickly relative to the Chronic Training Load (CTL). I need to take a more measured approach during week 3 to avoid overtraining or sickness.
I’ll reduce intensity and time in week 3 in an effort to keep ATL and CTL value within 10 units of each other.
Week 3: Tuesday, November 11
Training goal achieved. Now time to reflect and thank those that gave for us.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 3: Thursday, November 13
Training objective was Threshold Intervals (LT2 above), but just couldn’t execute. Poor sleep and diet impacted the work.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Have to refocus and spend more time on core stability in order to handle the over LT2 pace.
Week 3: Friday, November 14
Nice easy walk in the fall air. Will do some core work also.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 4: November 17 to 23
Rest week. Light training focused on recovering from training load.
Week 5: Tuesday, November 25
Ease back into training with a 4 KM run at LT1. Breathing felt easy, nice to be running again.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 5: Thursday, November 27
About 5.5KM on the treadmill. Began with about 3 KM at LT1. Did 3x400m efforts at 8.1 MPH near the end to add some TSS.
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 5: Friday, November 28
A little busy today. Instead of a run, did full-body resistance training followed by stretching.
An aside: I’ve been aware of tight hip flexor on my left side for years. I am slowly correcting this imbalance through PNF1-type stretching. I recently started following these exercies from Precision Movement. If you have similar issue or just interested in learning more, check out their video: How to Fix Hip Flexors.
Week 5: Saturday, November 29
Plan is to increase the TSS and back to increasing CTL. Goal achieved. A bit of unstructured speed work at the end of the session, but overall good to turn the legs over and get the heart rate above LT2 for a bit. In addition, yesterday’s hip flexor stretching was noticable today as the left leg provided better push off the ground.
TSS: 55, CTL: 17, ATL: 15
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 6: Monday, December 1
Getting back into the training. Full LT1 treadmill session.
TSS: 8.33, CTL: 17, ATL: 16
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 6: Tuesday, December 2
Treadmill session, warm-up followed by 2 x 2 km sub-LT2. Breathing light considering proxicity to LT2 threshold.
TSS: 33.21, CTL: 17, ATL: 21
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 6: Thursday, December 4
Warm enough for an outside run. Started slow and let the pace slowly build. Ran completely free. Near the end of the run, I intentially slowed in an effort to keep below LT2. However, reviewing the numbers after the run, dipped above LT2. Can feel the effort now, hopefully, the correct amount of stimulus.
Note: Ignore the heart rate spike around 3 km, false reading.
TSS: 41.88, CTL: 17, ATL: 25
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 6: Sunday, December 7
Mixed up the running, ran most of the way home from the next town. Very enjoyable view and +2 degrees celcuis. The effort was a slow increase in effort of the 11+ km. Maximium heart rate was 131 BPM, well under LT2.
TSS: 32.67, CTL: 16, ATL: 17
Red line -> Heart Rate, Blue line -> Pace, Green Line -> Ambient Temperature, Grey Area -> Elevation.
Week 6: Summary
ATL and CTL now within 10 units. With Winter arriving, it will be challenging to keep ATL at 25 for weeks 6-9, but that’s the goal.
Here is the Performance Manager Chart at the end of week 6:
