The distances
What Each Distance Actually Is
The names are consistent. The races underneath them vary more than most people expect. Here are the standard formats — what WattX builds plans and simulates Race Pacing Targets around.
- Swim750 m
- Bike20 km
- Run5 km
High intensity. Every discipline is short enough to race near max effort. Technique errors are immediately punished. Margins are small.
- Swim1,500 m
- Bike40 km
- Run10 km
The standard format. Hard enough to require pacing discipline, short enough that fitness can compensate for moderate tactical errors. The benchmark distance.
- Swim1,900 m
- Bike90 km
- Run21.1 km
The distance where nutrition becomes a discipline. Overcooking the bike destroys the run. Pacing is the race within the race.
- Swim3,800 m
- Bike180 km
- Run42.2 km
A logistics and execution event as much as a fitness event. The training load required is a commitment measured in months, not weeks.
Training demand
The Real Cost Before You Get to the Start Line
Distance determines training volume. Training volume determines what else you can do with your life during the build. This is the constraint most athletes underestimate when choosing a distance.
Peak weekly hours scale with your goal finish time — the same distance can mean very different load if you are racing to finish versus chasing a PR. The ranges below match what the WattX plan engine targets at peak block for typical finish-time goals (not elite splits).
These are peak-block hours — what your biggest training weeks will look like, not the average across 20 weeks. Most age-groupers aiming only to finish an Ironman land in the lower half of the range; a sub-10-hour race goal pushes toward the top (~16 hours). A 70.3 build that peaks at 12 hours means several Sundays with a long ride and a short run off the bike. If that isn’t realistic given your life right now, the distance isn’t right.
Signing up for a 70.3 or full Ironman without having completed an Olympic distance first. The jump in training volume is significant, but the bigger issue is that you won't yet know how your body responds to multi-hour efforts, or what your pacing and nutrition errors actually are. Race an Olympic first. Use the data.
Decision framework
How to Pick the Right Distance for Right Now
The right distance is not the most impressive one on your bucket list. It’s the one that produces the best training stimulus given your current fitness, available time, and experience base.
| Your situation | Start here |
|---|---|
| First triathlon ever. Can swim, bike, and run but not simultaneously. | SPRINT |
| Done a sprint. Comfortable in open water. ~5–9 hours/week available at peak. | OLYMPIC |
| Multiple Olympics. Solid aerobic base. ~6–12 hours/week available at peak. | 70.3 |
| Completed a 70.3. Know your nutrition. Life can absorb ~8–16 hrs/week at peak. | IRONMAN |
| Returning from injury or break. Base fitness uncertain. | SPRINT |
| Strong runner or cyclist. New to swimming. | SPRINT → fix the swim first |
Ironman-distance racing is a legitimate athletic goal. But training for it on an insufficient base produces injury, burnout, and a first race you'll want to forget rather than repeat. The athletes who eventually do Ironman well almost universally built through the shorter distances first — not because they had to, but because it made them significantly faster when they got there.
What each distance trains
Different Distances. Different Physiological Targets
This matters because your WattX Race Plan should reflect the demands of your race — not a generic multi-sport programme. WattX builds distance-specific plans precisely because a sprint and a 70.3 require fundamentally different physiological emphases.
Sprint. Primarily aerobic-anaerobic threshold. You're racing at or near FTP on the bike and close to FT pace on the run. Speed work and VO₂ max intervals are directly race-relevant. Weakness: it punishes poor technique and transitions more than any other distance.
Olympic. Sustained threshold capacity. The bike is largely ridden at 85–95% FTP; the run at approximately FT pace. Aerobic efficiency improvements translate directly into time gains. The benchmark for measuring progress across seasons.
70.3. Fat oxidation and pacing discipline. The bike should be ridden at 75–85% FTP to leave the run intact. Nutrition is now a performance variable — see [Long-Course Nutrition Explained](/guides/nutrition-ironman-703).
Ironman. Metabolic efficiency and volume absorption. The race is won or lost in months of aerobic base work before the peak block begins. Race day itself is execution and nutrition management. Muscular endurance on the bike matters more than FTP alone.
On WattX
Where This Connects to Your Plan
When you use your WattX Race Plan PRO, the engine targets the specific physiological demands of your chosen distance. A sprint plan and a 70.3 plan built from the same athlete profile will produce different sessions, different intensity distributions, and different ramp rates.
The Race Simulator pre-populates pacing targets from your current CSS, FTP, and FT on Threshold Testing. If your thresholds are accurate, the simulator output tells you what pace is sustainable for your chosen distance on race day. The distance selection is not arbitrary — it calibrates everything downstream.
Pick your distance → calibrate your plan → test your thresholds (CSS, FTP, FT) → run the Race Simulator to see your target splits. If the simulator predicts a time that feels wrong, check your thresholds first — they're almost always the cause.
Racing sprint or Olympic for the first time? Read Your First Triathlon Explained the week before race day — transitions, kit, and race morning in one place.