IRONMAN 70.3 · Swansea Bay · 11 Jul 2027
How to train for IRONMAN 70.3 Swansea
The organiser sums up the bike at IRONMAN 70.3 Swansea in one word: Hilly. The run gets another: Flat. Both words are accurate. Most people read only the first. They spend the winter on climbs, ride the Gower like a hill race, and then meet 21 km of level road with nothing left to run it on.
Swansea is won and lost after the bike. The 913 m of climbing is real, but no single hill on it is long enough to decide anything. What the hills do is set the price of the run, and a Trained athlete's 6:02:21 depends on whether that price was paid on purpose.
By Kian Briel, founder. Analysed by engine 1, updated
What is actually on the road
The organiser's own course files, drawn the way the Event Analyzer draws a member's race.
- Swim1.86 km5 m upCourse file
- Bike90.1 km913 m upCourse file
- Run21 km182 m upCourse file
The swim is one loop from the Prince of Wales Dock, 1.9 km of what the organiser lists as harbour water, logged at 24 C in 2025 and 18 C the year before. From the exit it is a 500 m run to transition in East Burrows Car Park. There is an optional yellow bag with shoes in it for exactly that stretch.
The bike is what the organiser calls a 1.5 loop course of 90.1 km. It goes through Mumbles on roads that hug the Gower's coastal clifftops, heads out through Rural Swansea, and comes back along Swansea Bay into the city. Swansea runs a single transition, so the bike ends where it began, in the same car park.
The run is two loops from the city centre, out past the gold-coloured Swansea Arena towards Mumbles and back to the finish at the Marina. In the organiser's 2025 athlete awards it was voted the third best IRONMAN 70.3 run course in Europe, the Middle East and Africa.
Now the profile. The first 8 km of the bike are flat. After that the file holds 26 rises of 3 percent or steeper and 18 descents just as steep, spread over the next 75 km before the road reaches its final flat 6 km. The highest point, 155 m, turns up twice, near kilometre 35 and again near kilometre 63, which is the half loop showing itself. The run climbs 182 m across the whole leg without a single rise of 3 percent in it.
Course shape by distance
- Flat 80%
- Climbing 11%
- Descending 10%
The longest stretches
- Bike, climbing0.62 km2% of the bike
- Run, flat8.76 km42% of the run
- Run, flat7.69 km37% of the run
Each row is one unbroken stretch of the course that keeps the same shape the whole way. The number is how much of that leg you spend inside it, and it comes out the same whether you are fast or slow.
What this course asks of each leg
Twelve training dimensions scored for each leg against its own course, the way the Event Analyzer scores a member's race.
Aerobic endurance and muscular endurance, with the bike carrying both. The demand model scores them 85 and 83 for the bike leg, and threshold capacity and threshold durability sit level at 70 behind them. The bike is 54 percent of a Trained athlete's day, which is why the seven largest demands on the whole course belong to it. The run's leading pair reads 85 and 82. The swim's reads 85 and 81.
Two scores are particular to Swansea. High-intensity capacity reads 58 on the bike against 40 on the run, and the difference is those 26 rises. Only two of them take a Trained rider longer than five minutes. Every one of them invites a little more than steady power, and the engine, asked for a session from this bike file, compiles twelve efforts of 45 seconds in Zone 5 with three minutes of easy riding between them. That is the rhythm of the leg.
The other is the swim. Technical skill scores 73 there, against 39 on the bike, because the swim file turns back on itself more than once over a short stretch of water. Holding a line and holding speed through the turns is worth more here than in a straight point-to-point swim.
In band terms, the Trained reference swims 37:21, rides 3:15:55 at 182 W from an input of 3.03 W/kg at 75 kg, and runs 1:59:05. The Competitive band finishes in 5:12:23 from 4.15 W/kg at 75 kg and 4:20 /km threshold pace, riding 2:48:54 and running 1:41:11. The climbs do not make that difference. Holding 249 W over them and between them does, and then running well afterwards.
Heat has been part of the last two editions. The organiser logged highs of 28 C in 2026 and 28 C in 2025, after a cool 18 C in 2024 with a low of 7 C. Train for either.
- Aerobic endurance85
- Muscular endurance81
- Technical skill73
- Threshold capacity70
- Aerobic durability65
- Threshold durability65
- Fueling resilience55
- High-intensity capacity40
- Anaerobic capacity25
- Strength / force20
- Environmental resilience15
- Sprint power5
Nymiva reads what you can already show, from your own data
Connect your training history and the Focus Lab scores the same twelve dimensions this course demands against where you sit today. The gap between the two is what you train.
- MeasuredFrom your thresholds and testsThreshold power, threshold pace, critical swim speed and field tests you have done. The dimensions they can carry are scored directly.
- EstimatedFrom your training historyConnected activities are read for what they prove: long efforts, late-session fade, repeated hard work, fueling on long days. Each score says how it was read.
- ProxyFrom a stand-in, and named as oneWhere only an indirect signal exists, the score carries the proxy it came from and a lower confidence, never a number dressed as a measurement.
- UnmeasuredHonestly blankA dimension nothing in your data can answer stays unmeasured. It is never a zero, and the plan does not pretend to know it.
Every dimension ends in one word
- Develop the course asks more than you can show
- Maintain close enough to hold at the minimum dose
- Covered nothing to build here
- Unmeasured the course needs it, your data cannot say yet
Nymiva reads twelve dimensions on each side. The course side comes from the organiser's files. The athlete side comes from thresholds and connected training history, and each score carries a note on what it was read from and how far to trust it. There is a gap only where the course asks for more than the athlete can show, and each gap is then weighted by how much of race day it occupies. With the bike at 54 percent of the day and the swim at 10 percent, a small bike gap outranks a large swim one.
Nobody's data sits behind this page, so the season below starts from an assumption: the gaps are where the demands are highest. On that basis it lays out 24 weeks in 5 developmental blocks and a two-week taper. Aerobic endurance leads the first block in every sport. Threshold capacity and threshold durability lead the bike and the run through the second and third, while the swim turns to technical skill in the third. Muscular endurance leads the fourth, and aerobic endurance comes back to lead the fifth. A member's own season is built from their numbers and will order things differently.
Train the bike to protect the run
Which demands matter most across the whole race. A leg's demand counts for as much of the day as that leg takes, so a score of 85 on the bike outweighs the same score on the swim.
- 01Aerobic enduranceBike leg, 54% of the day85 × 54%46
- 02Muscular enduranceBike leg, 54% of the day83 × 54%45
- 03Threshold capacityBike leg, 54% of the day70 × 54%38
The bike takes 54% of the Trained reference band’s day, so its demands carry the most race weight. What the bike leaves in the legs is what the run gets.
Which demand gets a block, and when
The engine freezes one lead focus per sport on every developmental block, holds the rest at maintenance, and verifies before it reprioritises.
An illustration, not your plan. This page has none of your data, so the season below is the engine’s answer to one stated assumption: that your gaps line up with what IRONMAN 70.3 Swansea demands. Your own season is built from your history, your thresholds, the days you can train and the races you have entered, and it will differ from this in its priorities, its sessions and its load.
- 01Run muscular endurance, a practice block4 weeks
- 02Run aerobic endurance, a development block4 weeks
- 03Bike muscular endurance, a practice block4 weeks
- 04Bike aerobic endurance, a development block4 weeks
In the order the allocator places them, general first, most race-like last.
- Week 1PrepPrep
A lead-in week. It develops nothing by design.
- Weeks 2 to 5Foundation 1Closes with a recovery week
- PriorityBike aerobic endurance
- PriorityRun aerobic endurance
- PrioritySwim aerobic endurance
- SupportBike muscular endurance
- SupportRun muscular endurance
- SupportSwim muscular endurance
- SupportSwim technical skill
- SupportBike threshold capacity
- SupportBike threshold durability
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportRun threshold durability
- Weeks 6 to 9Foundation 2Closes with a recovery week
- PriorityBike threshold capacity
- PrioritySwim threshold capacity
- PriorityRun threshold durability
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportSwim aerobic endurance
- SupportBike muscular endurance
- SupportRun muscular endurance
- SupportSwim muscular endurance
- SupportSwim technical skill
- SupportBike threshold durability
- SupportRun threshold capacity
- Weeks 10 to 13Foundation 3Closes with a recovery week
- PrioritySwim technical skill
- PriorityBike threshold durability
- PriorityRun threshold capacity
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportSwim aerobic endurance
- SupportBike muscular endurance
- SupportRun muscular endurance
- SupportSwim muscular endurance
- SupportBike threshold capacity
- SupportSwim threshold capacity
- SupportRun threshold durability
- Weeks 14 to 17Event shaping 1Closes with a recovery week
- PriorityBike muscular endurance
- PriorityRun muscular endurance
- PrioritySwim muscular endurance
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportSwim aerobic endurance
- SupportSwim technical skill
- SupportBike threshold capacity
- SupportBike threshold durability
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportRun threshold durability
- Weeks 18 to 21Event shaping 2Closes with a recovery week
- PriorityBike aerobic endurance
- PriorityRun aerobic endurance
- PrioritySwim aerobic endurance
- SupportBike muscular endurance
- SupportRun muscular endurance
- SupportSwim muscular endurance
- SupportSwim technical skill
- SupportBike threshold capacity
- SupportBike threshold durability
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportRun threshold durability
- Weeks 22 to 23PeakPeak
The taper. Load comes down toward the race, content stays specific.
- Week 24RaceRace
Race week.
Held at maintenance between blocks
- Runmuscular endurance, aerobic endurance, aerobic durability, threshold capacity, threshold durability
- Bikemuscular endurance, aerobic endurance, aerobic durability, threshold capacity, threshold durability
- Swimaerobic endurance, aerobic durability, threshold capacity, threshold durability, muscular endurance, technical skill
Touches scheduled by each capability’s own decay, at a fraction of its development dose, so earlier work is still there on race day.
The sessions the blocks are built from
One entry per kind of work the block trains, at the intensity that work is meant to be done at. Where the same work runs at several lengths, the entry shows the span it grows across rather than one entry per length.
- Foundation 1 · Weeks 2 to 575 to 240 min
150 to 210 min at Zone 2
BikePower, Zone 2Trains aerobic capacity - Foundation 1 · Weeks 2 to 540 to 270 min
180 to 210 min at Zone 3, then 30 min at Zone 4
BikePower, Zone 3Trains aerobic capacity - Foundation 1 · Weeks 2 to 535 to 120 min
90 min at Zone 2
RunPace, Zone 2Trains aerobic capacity - Foundation 1 · Weeks 2 to 550 min
4 x 1.5 min at Zone 3, 6 min easy between
RunHeart rate, Zone 3Trains aerobic capacity - Foundation 1 · Weeks 2 to 545 to 51 min
4 x 8 min at Zone 2, 1 min easy between
SwimPace, Zone 2Trains aerobic capacity - Foundation 1 · Weeks 2 to 547 to 81 min
3 x 1000 m at Zone 3, 0.3 min easy between
SwimPace, Zone 3Trains aerobic capacity
12× rolling-course surges
0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, then 0.8 min at Zone 5, 3 min easy between
Compiled by the deterministic course compiler from the organiser’s file: the course’s one repeatable requirement, rehearsed at a dose the progression allows.
- Bike
- 67 min
- Trains threshold durability
- Supports muscular endurance
- Supports high intensity capacity
24 weeks, laid out backwards from race day
The shortest runway Nymiva builds for this event type, with its blocks, recovery weeks, taper and race week in place.
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- Prep
- Foundation
- Event shaping
- Peak
- Race
- Recovery week
Your own season carries these same phases on your own dates, with the load solved from your fitness and the days you can train, and it changes when your data does.
What each level does on the day
Reference finish times per peer band, the pacing plan the model holds each band to, and where the day is decided.
| Band | Swim | Bike | Run | Finish |
|---|---|---|---|---|
| Recreational2:11 /100m critical swim speed · 2.47 W/kg at 75 kg · 6:08 /km threshold pace | 0:44:04 | 3:38:29 | 2:23:12 | 6:55:45 |
| Trained1:51 /100m critical swim speed · 3.03 W/kg at 75 kg · 5:06 /km threshold pace | 0:37:21 | 3:15:55 | 1:59:05 | 6:02:21 |
| Competitive1:36 /100m critical swim speed · 4.15 W/kg at 75 kg · 4:20 /km threshold pace | 0:32:18 | 2:48:54 | 1:41:11 | 5:12:23 |
| Elite1:26 /100m critical swim speed · 5.27 W/kg at 75 kg · 3:50 /km threshold pace | 0:28:56 | 2:34:16 | 1:29:30 | 4:42:42 |
Pacing plan
- 0 km0%30.8 km/h15:53
- 8.16 km3.8%15.7 km/h0:36
- 8.31 km0.1%30.3 km/h2:46
- 9.71 km6.3%10.7 km/h3:26
- 10.3 km-0.4%32.8 km/h0:31
- 10.6 km3.1%17.7 km/h0:53
- 10.9 km-3.1%45.8 km/h0:13
- 11 km0%30.8 km/h1:31
75 more segments in the full plan.
- Run: reach 4:20 /km and this course gives back 49:58.
Where it is decided
On the run, by what the bike took.
The climb the engine singles out on the bike is 621 m at 6.9 percent, near kilometre 80, and it accounts for 2.1 percent of the leg. Nothing on the bike decides the race alone. The 26 rises together spend your legs a few watts at a time, and because none of them lasts long enough to scare you into backing off, it is easy to spend far more than you planned.
Then the course gives you a reprieve you have not earned. A 1.2 km descent at 6.5 percent drops you onto the last 6 km of flat road, and you reach East Burrows Car Park feeling fresher than you are.
The run collects. Two long level stretches of 8.8 km and 7.7 km carry 42 and 37 percent of the leg between them. From an input of 5:06 /km threshold pace, the Trained reference runs 1:59:05, and on road this flat there is no hill to blame and no descent to recover on. A runner who rode 182 W everywhere holds pace on those two stretches. A runner who rode it on the flat and well above it on every rise watches the Marina get no closer.
Getting it wrong
Riding the opening like it matters. The first 8 km are dead flat, the legs have just done a 500 m run from the swim exit, and the whole field is together. It feels like the place to bank time. It is the place to settle, because the rises start straight after and keep coming until the last 6 km.
Training for the wrong hills. Swansea reads as a climbing race, so people build long seated climbs into their weekends. The course never asks for one. Strength and force scores 48 on the bike against 85 for aerobic endurance, and the longest single rise costs a Trained rider a little over six minutes. What it asks for is the same power on the twentieth short ramp as on the first.
Trusting the word Flat. With highs of 28 C in 2025 and 28 C in 2026, a flat run is not an easy one, and it starts after 3:15:55 of rising and falling road. Run the first loop at the pace the day gives you, not the pace you trained for in spring.
Conditions on the day
- 2026high 28 C, low 17 C
- 2025high 28 C, low 11 Cwater 24 C
- 2024high 18 C, low 7 Cwater 18 C
From the organiser’s own records. Not a forecast.
Every session is a claim, every block is a test
A plan is not a calendar. Each key session states what it trains and how that is checked, and each block ends with a public verdict before the next one is chosen.
What a block promises
Bike aerobic endurance moves from your baseline to a stated target by the end of Foundation 1
- The baseline is your measured score when the block starts. The target is the score the model predicts for it.
- Verified at the block’s recovery week, by a field test or a refresh of the supply read from your history.
- Confidence rises by agreement between independent signals, never by one metric crossing a line.
- A block that misses its target is a public miss. The next block is chosen from what was proven, not from what was planned.
- 01Stimulus achievedThe work landed in the zone the session named, for the dose it named.
- 02Partially achievedSome of the work landed. The session banks what it can prove.
- 03Not achievedThe load may have been there. The stimulus was not, so nothing is banked.
- 04Data insufficientNo usable stream. The session is neither credited nor blamed.
- Session verified
- Progression banked
- Block verified
- Priority reassessed
- Plan adapted
Your numbers, this course
Analyze IRONMAN 70.3 Swansea against my fitness
The same simulation and the same Focus Lab read, on your thresholds instead of a band’s. Three numbers give a finish estimate and a partial read. A connected history gives the whole table.
The first 14 days are free.
- Trained band finish
- 6:02:21
- Of the day on the bike
- 54%
- Dimensions scored per leg
- 12
- Season runway shown
- 24 wk
Questions people ask
- How hilly is the IRONMAN 70.3 Swansea bike course?
- The organiser tags it Hilly, and the file agrees. The 90 km climbs 913 m in total, flat for the first 8 km and then broken into 26 rises of 3 percent or steeper. The steepest sustained ramp is 621 m at 6.9 percent, near kilometre 80.
- What water temperature should I expect for the Swansea swim?
- The organiser logged 24 C in 2025 and 18 C in 2024, and has no reading for 2026. The swim is one loop from the Prince of Wales Dock. The wetsuit rule is not on the course page, so check it in race week.
- Is the IRONMAN 70.3 Swansea run course flat?
- Yes. It is two loops of 21.1 km with 182 m of climbing in total and no rise of 3 percent or more anywhere in the file. It runs from the city centre past Swansea Arena towards Mumbles and back to the finish at the Marina.
- How far is it from the swim exit to transition?
- 500 m, to transition in East Burrows Car Park. The organiser offers an optional yellow bag with shoes for that run. Swansea is a single transition, so you come back to the same car park after the bike.
Course data from the organiser’s published files, analysed 23 Sept 2026 by engine 1, demand model 4. Reference times are simulated for a peer band at a stated reference athlete and are not a prediction for anyone. Nothing on this page is medical advice.
IRONMAN® and IRONMAN 70.3® are registered trademarks of World Triathlon Corporation. Nymiva is an independent training platform and is not affiliated with, sponsored by or endorsed by World Triathlon Corporation. Course data is read from the organiser’s public course pages for the purpose of describing the event.