30 km Long Run · London 2026 vs Berlin 2025
Comparative analysis of Sabastian's 30 km long-run performance across two sessions — 5 km split structure, cumulative pacing, heart-rate response, and Berlin 2025 ¹³C substrate oxidation.
This comparison evaluates Sabastian's 30 km long run across two sessions using 5 km split data and session metrics. The structure allows assessment of pacing pattern, cumulative time gain, late-run progression, and cardiovascular demand.
London 2026 completed the run in 1:30:13, compared with 1:31:20 in Berlin 2025 — 1 minute 7 seconds faster overall.
Sabastian's London 2026 run was both faster and slightly less costly internally. The run was completed at a lower average heart rate (154 vs 156 bpm) despite the faster overall time, suggesting improved aerobic efficiency and stronger late-run execution.
| Distance | LDN Split | LDN Running | BER Split | BER Running | Split Δ | Cumulative Δ |
|---|---|---|---|---|---|---|
| 5 km | 14:59 | 14:59 | 15:04 | 15:04 | +0:05 | +0:05 |
| 10 km | 14:55 | 29:54 | 15:03 | 30:07 | +0:08 | +0:13 |
| 15 km | 15:41 | 45:35 | 15:51 | 45:58 | +0:10 | +0:23 |
| 20 km | 15:45 | 1:01:20 | 15:57 | 1:01:55 | +0:12 | +0:35 |
| 25 km | 14:47 | 1:16:07 | 15:05 | 1:17:03 | +0:18 | +0:56 |
| 30 km | 14:06 | 1:30:13 | 14:09 | 1:31:12 | +0:03 | +0:59 |
| Metric | London 2026 | Berlin 2025 |
|---|---|---|
| Distance | 30 km | 30 km |
| Time | 1:30:13 | 1:31:20 |
| Pace | 3:00.4 /km | 3:02.7 /km |
| Average heart rate | 154 bpm | 156 bpm |
| Max heart rate | 174 bpm | 171 bpm |
London opened slightly faster and extended that advantage through each 5 km block. The time gap increased progressively from 5 seconds at 5 km to 56 seconds by 25 km, indicating persistent superiority rather than a single isolated segment.
The most decisive section was 20–25 km, where Sabastian ran 14:47 in London versus 15:05 in Berlin — stronger durability under fatigue.
| Fastest split — London | 14:06 |
| Fastest split — Berlin | 14:09 |
| Slowest split — London | 15:45 |
| Slowest split — Berlin | 15:57 |
| Final 10 km — London | 28:53 |
| Final 10 km — Berlin | 29:14 |
| Avg HR — London | 154 bpm |
| Avg HR — Berlin | 156 bpm |
| Max HR — London | 174 bpm |
| Max HR — Berlin | 171 bpm |
| Verdict | Faster + lower HR |
| Category | Better session |
|---|---|
| External output (pace) | London |
| Internal cost (heart rate) | London |
| Late-run durability | London |
| Pacing control | London |
Sabastian shows a strong long-run profile characterized by progressive control and late-run speed preservation. The final 10 km were completed in 28:53, compared with 29:14 in Berlin, despite already holding an advantage earlier in the run.
That pattern is consistent with good aerobic durability, strong substrate management, and preserved neuromuscular efficiency as fatigue accumulated.
Producing a faster overall performance at a slightly lower average heart rate generally implies lower relative strain for a given pace — better aerobic conditioning, improved economy, or better readiness at the time of testing.
The higher maximum heart rate in London is not necessarily negative. It likely reflects the ability to access a higher ceiling late in the run while still maintaining better overall control.
What is ¹³C? Carbon comes in two natural, stable forms: the common one (¹²C) and a slightly heavier one (¹³C). Both are safe, non-radioactive, and behave almost identically in the body. The heavier ¹³C simply acts as a tag that can be tracked.
Why it works as a tracer. Different plants contain naturally different amounts of ¹³C. Sugars from plants like corn, sugar cane, and maize are naturally enriched in ¹³C — they carry more of the heavy carbon than the food the body was running on beforehand. That difference is what makes tracking possible.
How the measurement works. When the body burns carbohydrate for fuel, the carbon atoms are exhaled as CO₂. By collecting breath samples at each 5 km checkpoint and measuring the ratio of ¹³C to ¹²C in that CO₂, we can see how much of the fuel being burned came from the drink versus from the body's own stores.
What the numbers mean. The δ¹³C value (in ‰, "per mille") describes how much ¹³C is in the breath. A more negative number means the body is still mostly burning its own fuel; a less negative number (closer to zero) means more of the ingested drink is being oxidised. A climbing curve means the fuel strategy is working and the gut is successfully delivering carbohydrate to the working muscles.
In this session: a ¹³C-enriched carbohydrate drink was ingested during the Berlin 2025 run, and breath samples were collected at each 5 km checkpoint. The rising δ¹³C signal shows the ingested fuel was being used in increasing amounts, while the calculated oxidation rate (g·h⁻¹) translates that signal into how many grams of ingested carbohydrate were being burned per hour.
At the start of the run, Sabastian's body was burning mostly its own stored fuel (body fat and liver and muscle glycogen). As the session went on, more and more of the carbs he was drinking and eating started showing up in his breath — meaning his body was successfully absorbing them and using them for energy instead of relying only on internal reserves. The "carbon pool" is simply the mix of fuel molecules his body is actively burning at that moment; early on it's dominated by his own stores, and later it fills up with the carbs he's taking in.
| Checkpoint | δ¹³C (‰) | CHOₑₓ (g·h⁻¹) |
|---|---|---|
| Baseline | −18.5 | — |
| 5 km | −11.3 | 45 |
| 10 km | −6.5 | 76 |
| 15 km | −5.0 | 84 |
| 20 km | −4.6 | 86 |
| 25 km | −3.6 | 95 |
| 30 km | −3.0 | 100 |
The steep δ¹³C rise between baseline and 10 km (−18.5 → −6.5 ‰) reflects rapid absorption and oxidation of ingested carbohydrate as intake begins to dominate the fuel mix. The curve then flattens through the mid-run as the gut–oxidation pathway approaches steady state.
A further rise into the final 10 km — reaching ~100 g·h⁻¹ at 30 km — suggests Sabastian was still increasing exogenous CHO oxidation late in the session. This is a favorable substrate-management profile for long-duration efforts.
- London 2026 was clearly Sabastian's stronger performance. He was faster overall and faster in every single 5 km split.
- The advantage accumulated progressively. The gap widened steadily from 5 s at 5 km to 59 s at 30 km — no single early surge.
- The 20–25 km segment was decisive. This phase often reveals durability, and Sabastian gained the largest split advantage (+18 s) here.
- Faster pace combined with lower average heart rate. A strong indicator of improved endurance efficiency and better aerobic conditioning.
- Late-run execution was superior in London. The final 10 km were materially faster, supporting better fatigue resistance and pacing control.
- Berlin 2025 substrate data show excellent CHO oxidation capacity. Reaching ~100 g·h⁻¹ of exogenous CHO oxidation indicates a well-trained gut — a capability likely carried forward into London.
Overall, London 2026 represents Sabastian's better 30 km long-run execution both externally and internally. He ran faster overall, opened with control, built the advantage progressively, and showed superior late-run durability.
The lower average heart rate alongside the faster performance strengthens the interpretation that London reflects improved aerobic efficiency and a cleaner endurance profile. The data suggest better resistance to fatigue, better pacing control, and a stronger capacity to maintain speed deep into the run.