Sebastian's First Half Marathon: Breaking 2 Hours in Bogota

Why This Build Is Worth Studying

Sebastian came to me wanting one thing: break 2 hours in his first half marathon. No base of marathon training behind him, no history of 20+ km weeks. Just a goal, a race on the calendar in Bogota, and 12 weeks to get ready. Racing at altitude (Bogota sits around 2,640m) made the target more ambitious than it looks on paper — oxygen delivery is compromised, and pacing errors get punished harder than at sea level.

What makes this build worth writing about isn't a heroic volume number. It's the opposite. The training file shows a modest, sensible progression — one that respected the athlete in front of me rather than a generic template. I want to walk through exactly what we did, because the lessons here apply to most first-time half marathoners, not just the ones training above 2,500 meters.

The Starting Point

Sebastian's file opens the week of April 13th with a single run of 9.5 km at a TSS of 75. That's the entire week — one session. This tells you two things: we were building a base almost from scratch, and every session had to count. There was no room for junk mileage because there wasn't much mileage to begin with.

Over 12 weeks, Sebastian logged 12 total workouts (essentially one key run per week) totaling 155.2 km and 904 TSS. That's an average of about 13 km per week — low by half marathon standards, but appropriate for where he started. This is a point I make constantly with new athletes: the plan has to match the runner's history, not the race distance's reputation.

The Progression, Week by Week

Here's how the volume moved:

• Apr 13: 9.5 km (TSS 75)
• Apr 20: 11.5 km (TSS 96)
• Apr 27: 13.5 km
• May 4: 11.5 km (a pullback week)
• May 11: 9.5 km (TSS 84) — another step back
• May 25: 17.5 km (TSS 142) — a jump after a gap week
• Jun 1: 18.5 km
• Jun 15: 20.5 km (TSS 169) — peak week and longest single session
• Jun 29: 16.5 km (TSS 136) — beginning of taper
• Jul 6: 13.5 km (TSS 104)
• Jul 13: 11.5 km (TSS 91)
• Jul 20: 2.0 km (TSS 7) — race week shakeout

A few things stand out. First, this wasn't a straight linear ramp. There are two clear step-backs (early May), which is exactly what you want to see in a runner without a deep aerobic history — the body needs recovery weeks to absorb load, not just accumulate it. Second, the volume never got dangerous. The peak week, 20.5 km, is still a conservative number for a half marathon build. Research on recreational half marathon training backs this up: total training volume and longest run are both associated with performance, but the relationship isn't infinite — injury risk climbs when volume or single-run distance rises too sharply relative to what the runner has adapted to [PMID:32421886]. Sebastian's longest run before race day, 20.5 km, was already essentially race distance. That's a deliberate choice, not an accident — with limited weeks and a runner new to the distance, I'd rather have him experience close to 21.1 km once under control than chase multiple long runs and risk breakdown.

The Hardest Sessions

Looking at TSS, the five hardest sessions of the block were:

1. Jun 21 — Endurance (race-pace segment) — 20.5 km — TSS 169
2. May 31 — Endurance — 17.5 km — TSS 142
3. Jul 5 — Endurance (race-pace segment) — 16.5 km — TSS 136
4. Jul 11 — Endurance — 13.5 km — TSS 104
5. Apr 26 — Endurance — 11.5 km — TSS 96

Notice the pattern: every single hard session in this build was an endurance run, several explicitly labeled as race-pace work ('Trayecto de Carrera'). There's no interval sessions, no VO2max work in this file. For a first-time half marathoner at altitude, that was the right call. The physiological priority for someone new to the distance is building the aerobic engine and teaching the body — and the mind — what race pace actually feels like for 90+ minutes. Half marathon performance in recreational runners correlates strongly with aerobic training consistency rather than high-intensity work volume [PMID:36326961]. Sebastian didn't need more speed. He needed more time on his feet at a controlled, sustainable effort, repeated often enough that his body stopped treating it as novel stress.

The Taper

The taper here is textbook simple, which is exactly the point. From the peak week of 20.5 km, volume dropped:

• 16.5 km → 13.5 km → 11.5 km → 2.0 km (race week)

That's roughly a 20%, then 18%, then 15% weekly reduction, tapering down to a shakeout jog in the final week. No last-minute long runs, no attempts to "prove fitness" close to race day. The taper's job is to let training-induced fatigue dissipate while preserving the fitness already built — and the data shows we trusted that process rather than second-guessing it in the final 10 days.

Why Altitude Mattered

Bogota's elevation adds a layer most half marathon guides don't address. Reduced partial pressure of oxygen means a given pace feels harder and heart rate runs higher for the same output compared to sea level. This is part of why I kept intensity almost entirely in the aerobic, controlled range throughout the build — high-intensity efforts at altitude carry a higher cardiovascular cost and a higher injury/setback risk if the runner isn't adapted. It's also worth noting, more broadly, that endurance exercise — even at reasonable volumes like Sebastian's — produces measurable cardiac remodeling and load, and this appears consistent across age groups engaged in prolonged endurance activity [PMID:40667749]. None of that is a reason to avoid endurance training; it's a reason to progress it patiently, which is what a 12-week, single-session-per-week structure with built-in pullback weeks is designed to do.

Race Day

Sebastian broke 2 hours in his debut half marathon. For a runner who started this block with a single 9.5 km run and built through a modest, interrupted progression, that result is the payoff of consistency over ambition. He didn't run the biggest weeks. He ran the right weeks for where he was, then trusted the taper to deliver him to the start line rested rather than raced-out.

What Other Runners Can Take From This

You don't need big volume to break 2 hours. Sebastian's peak week was 20.5 km. If your weekly mileage is modest but consistent, and your longest run approaches race distance in a controlled way, you have a real shot at the sub-2 barrier — it's about how you build, not how much you accumulate [PMID:32421886].

Step-back weeks are not wasted weeks. The dips in early May weren't setbacks in this file — they were the plan working. If your training log shows a straight line up with no pullbacks, that's usually a red flag, not a strength.

Most of your hard work should be at or near race pace. Every demanding session in this build was an endurance run, several explicitly at race pace. For a first-time half marathoner, rehearsing the actual effort you'll hold on race day matters more than chasing VO2max numbers on the track.

Taper on purpose. The steady, unhurried decline from 20.5 km down to a 2 km shakeout is not complicated, and that's the point. Resist the urge to add one more long run in the final two weeks.

Respect the environment. If you're racing at altitude, or in heat, or anywhere that changes the physiological cost of a given pace, build your intensity distribution around that reality rather than around a plan written for sea level.

A Closing Note

I don't think Sebastian's build looks impressive on paper next to marathon training logs with 100+ km weeks. It isn't supposed to. It's supposed to match the runner and the goal. That match — more than any single workout — is what got him under 2 hours in his first half marathon, at altitude, on a modest but honest 12 weeks of work.

References

• Fokkema T, van Damme AADN, et al. Training for a (half-)marathon: Training volume and longest endurance run related to performance and running injuries. Scand J Med Sci Sports. 2020. [PMID:32421886]
• Nikolaidis PT, Knechtle B. Participation and performance characteristics in half-marathon run: a brief narrative review. J Muscle Res Cell Motil. 2023. [PMID:36326961]
• Frandsen J, Aaroe M, et al. Cardiac Effects of Prolonged Endurance Exercise in Young and Older Athletes. Scand J Med Sci Sports. 2025. [PMID:40667749]