Triathlon Race Distances & Run Segments
| Format | Swim | Bike | Run | Total |
|---|---|---|---|---|
| Sprint | 750m | 20km | 5km | ~1:00–1:30h |
| Olympic | 1.5km | 40km | 10km | ~2:00–2:45h |
| 70.3 / Half Ironman | 1.9km | 90km | 21.1km | ~4:00–6:00h |
| Full Ironman | 3.8km | 180km | 42.2km | ~8:00–17:00h |
How Much Slower is Your Triathlon Run?
After the swim and bike legs, most athletes run significantly slower than their standalone running pace. Here are typical slowdown factors:
| Format | Typical Run Slowdown vs Standalone |
|---|---|
| Sprint | 0–5% slower |
| Olympic | 5–10% slower |
| 70.3 / Half Ironman | 8–15% slower |
| Full Ironman | 15–25% slower |
Ironman Run Pacing Strategy
The Ironman marathon is unlike any standalone marathon. After 3.8km of swimming and 180km of cycling, your legs are already fatigued and your glycogen stores partially depleted.
Strategy: Break the marathon into thirds. Run km 1–14 at a pace that feels almost too easy. Maintain pace km 14–28. Race the final 14km if you have anything left. Walk through all aid stations to take in nutrition and lower heart rate.
💡 A common Ironman mistake: running the first 5km at standalone marathon pace. This leads to a catastrophic walk/shuffle from km 25 onward. Start conservative, finish strong.
Brick Run Effect
The 'brick' feeling — heavy, unresponsive legs in the first 2–5km of the run — is caused by the sudden switch from cycling to running muscle recruitment patterns. It typically fades after 3–5 minutes. Starting the run at 10–15 seconds/km slower than goal pace for the first 2km helps manage this transition.
Frequently Asked Questions
What run pace should I target for an Ironman?
Add 15–25% to your standalone marathon pace as a starting estimate. If you run a 4:00 standalone marathon (5:41/km), target 4:35–5:00 in an Ironman (6:31–7:06/km). Many experienced Ironman athletes use their standalone half marathon time × 2.3–2.5 as a marathon target.
How do I calculate my 70.3 run pace?
Start with your standalone half marathon pace and add 5–12%. A runner who does 1:45 standalone may target 1:52–1:58 in a 70.3. Use the calculator above to model different scenarios.
What is a good Ironman run time?
For age groupers, 3:30–4:30 is a competitive Ironman marathon. Under 3:00 is elite age group level. Many first-time Ironman athletes target simply running the whole way — not walking — which typically means 4:30–5:30.