IRONMAN 70.3 · Goseong · Last raced 14 Jun 2026
How to train for IRONMAN 70.3 Goseong
Goseong's own course page tags the bike rolling and the run hilly, and athletes arrive braced for climbing. The climbing is real but small. On the bike the rises are short coastal kicks, none of them higher than a few dozen metres, and a Trained rider spends about 86 percent of the leg on flat road. On the run there is one big hill on the loop. What the organiser's own record says more loudly is warmth. Its recorded highs reached 30 C in 2024 and 27 C the year before.
So read this race as a long, warm, mostly flat day with a few sharp interruptions. The organiser has not yet published the date of the next edition, and this page reads the course as it was last raced.
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.
- Swim1.9 kmDistance only
- Bike89.3 km499 m upCourse file
- Run20.6 km in 3 laps449 m upCourse file
The swim is one lap of 1.9 km, starting from Danghangpo inside the Goseong Dinosaur Expo Park, with a rolling pontoon start. The organiser describes a large, protected stretch of sea surrounded by mountains, and logged it at 22 C in 2025 and 25 C in 2024.
The bike starts from Danghangpo too and heads out along the Hallyeohaesang National Park on a single out-and-back of 89.3 km. Its profile never climbs far above the sea. The first 24 km carry a cluster of short rises, the steepest two at 6.8 percent, one of them 293 m long and the other 482 m. Then the road flattens for close to 30 km through the middle of the leg, and the engine gives one 18.6 km flat stretch there a fifth of the bike leg on its own. From kilometre 53 the short rises return, and the last 10.5 km run flat to the finish of the leg.
The run is three loops through the Goseong Dinosaur Expo Park and along a road the organiser describes as shaded by Bald Cypress trees. It is generally flat, in the organiser's words, with one big steady hill, 500 m up and 500 m down at 7 percent. The file reads the sharpest part of it more steeply, 153 m at 13.7 percent. Either way, the climb is a small slice of the leg. The longest flat stretch of the run takes 22 percent of it.
Course shape by distance
- Flat 89%
- Climbing 5%
- Descending 6%
The longest stretches
- Bike, flat18.6 km20% of the bike
- Run, climbing0.15 km1% of the run
- Run, flat4.67 km22% 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.
On all three legs, aerobic endurance and muscular endurance lead. The bike reads 85 and 81, the run 85 and 85, the swim 85 and 80. Because the bike is more than half of a Trained athlete's day, the top seven places in the cross-leg ranking all belong to it.
Two scores set Goseong apart from a cool, flat half-distance triathlon. Environmental resilience reads 60 on every leg, and the organiser's weather record shows why. High-intensity capacity reads 58 on the bike and 55 on the run, which is the short rises and the run's hill. Hand this bike to the engine and it builds a session of a dozen efforts of 45 seconds, hard, each one followed by six and a half minutes of easy riding. That ratio is the course. The kicks are short and far apart, and the riding between them is where the leg is spent.
The bands put numbers on it. A Trained athlete swims 38:12, rides 3:01:31 at 182 W and runs 1:57:45, for 5:47:28. The Competitive band finishes in 5:03:40 from 4.15 W/kg at 75 kg and 4:20 /km threshold pace. It gains 21 minutes on the bike and 18 on the run, most of it on flat road.
The organiser's cut-offs run from each athlete's own swim start: 1:10:00 for the swim, 5:30:00 for the bike, 8:30:00 for the finish.
- Aerobic endurance85
- Muscular endurance80
- Threshold capacity70
- Aerobic durability65
- Threshold durability65
- Environmental resilience60
- Fueling resilience55
- Technical skill55
- High-intensity capacity40
- Anaerobic capacity25
- Strength / force20
- 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 the course and the athlete on the same twelve dimensions. The course side comes from the route files. The athlete side comes from thresholds and connected training history, every score carrying a note on where it came from and how much weight it can bear. A gap exists only where the course asks for more than the athlete can show, and gaps are ranked by how much of the day they cover.
Nobody's data stands behind this page. The season below takes the plainest assumption, that the gaps fall where the demands are highest, and lays out 24 weeks in 5 developmental blocks with a two-week taper. Aerobic endurance leads the first and the last of them in all three sports. Threshold durability leads the second on the bike and the run, threshold capacity the third, and muscular endurance the fourth. A member's own season is built from their numbers and will disagree with this one.
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, 52% of the day85 × 52%44
- 02Muscular enduranceBike leg, 52% of the day81 × 52%42
- 03Threshold capacityBike leg, 52% of the day70 × 52%37
The bike takes 52% 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 Goseong 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 aerobic endurance, a development block4 weeks
- 02Run muscular endurance, a practice 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
- SupportRun muscular endurance
- SupportBike muscular endurance
- SupportSwim muscular endurance
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportBike threshold durability
- SupportRun threshold durability
- SupportSwim aerobic durability
- Weeks 6 to 9Foundation 2Closes with a recovery week
- PriorityBike threshold durability
- PriorityRun threshold durability
- PrioritySwim aerobic durability
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportRun muscular endurance
- SupportSwim aerobic endurance
- SupportBike muscular endurance
- SupportSwim muscular endurance
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- Weeks 10 to 13Foundation 3Closes with a recovery week
- PriorityBike threshold capacity
- PriorityRun threshold capacity
- PrioritySwim threshold capacity
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportRun muscular endurance
- SupportSwim aerobic endurance
- SupportBike muscular endurance
- SupportSwim muscular endurance
- SupportBike threshold durability
- SupportRun threshold durability
- SupportSwim aerobic durability
- Weeks 14 to 17Event shaping 1Closes with a recovery week
- PriorityRun muscular endurance
- PriorityBike muscular endurance
- PrioritySwim muscular endurance
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportSwim aerobic endurance
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportBike threshold durability
- SupportRun threshold durability
- SupportSwim aerobic durability
- Weeks 18 to 21Event shaping 2Closes with a recovery week
- PriorityBike aerobic endurance
- PriorityRun aerobic endurance
- PrioritySwim aerobic endurance
- SupportRun muscular endurance
- SupportBike muscular endurance
- SupportSwim muscular endurance
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportBike threshold durability
- SupportRun threshold durability
- SupportSwim aerobic 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
- Runaerobic endurance, muscular 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
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× course-matched climbs
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, 6.5 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
- 106 min
- Trains anaerobic capacity
- Supports strength force
- Supports muscular endurance
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.
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- 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 | 0:45:05 | 3:17:01 | 2:21:36 | 6:33:42 |
| Trained1:51 /100m critical swim speed · 3.03 W/kg at 75 kg · 5:06 /km threshold pace | 0:38:12 | 3:01:31 | 1:57:45 | 5:47:28 |
| Competitive1:36 /100m critical swim speed · 4.15 W/kg at 75 kg · 4:20 /km threshold pace | 0:33:03 | 2:40:34 | 1:40:03 | 5:03:40 |
| Elite1:26 /100m critical swim speed · 5.27 W/kg at 75 kg · 3:50 /km threshold pace | 0:29:36 | 2:26:39 | 1:28:30 | 4:34:45 |
Cut-offs, Trained band
- Swim1:10:00+0:31:48 margin
- Bike5:30:00+1:45:17 margin
- Finish8:30:00+2:42:32 margin
Pacing plan
- 0 km0.3%29.3 km/h2:48
- 1.37 km-3.3%46.7 km/h0:14
- 1.55 km0.2%29.8 km/h6:11
- 4.63 km6.8%10.1 km/h1:45
- 4.92 km2.3%20.5 km/h0:53
- 5.22 km-5.8%57.3 km/h0:36
- 5.79 km0.2%29.8 km/h2:29
- 7.02 km3.8%15.7 km/h0:36
42 more segments in the full plan.
- Run: reach 4:20 /km and this course gives back 43:48.
Where it is decided
In the flat middle of the bike, and in what it leaves for the run.
Close to 30 km of the out-and-back is flat road with nothing to pace against. It is where a Trained rider spends the largest single block of the day, and it is where warm weather does its quiet work. A rider who holds 182 W through it, drinking to the conditions, reaches the second set of short rises with legs to spare. A rider who pushes the flat because it feels easy arrives there hot and has nothing for the kicks.
Then the run. Three loops, three passes of the hill, and a long flat stretch that is 22 percent of the leg. The hill is the part people remember. The flat is where the time goes.
Getting it wrong
Training for hills that are not there. The run is labelled hilly and the bike rolling, and athletes build strength for climbs. Strength and force read 46 on the bike and 51 on the run, well behind aerobic endurance at 85. Train the long, steady effort first.
Ignoring the weather record. 2025 peaked at 23 C, 2024 at 30 C. A plan built only in cool conditions meets its first warm three hours on race day.
Racing the first rises. The opening 24 km bring most of the bike's short climbs while the legs are fresh. Answer each one hard and the flat middle of the course, the part that decides the day, starts already in debt.
Conditions on the day
- 2025high 23 C, low 19 Cwater 22 C
- 2024high 30 C, low 18 Cwater 25 C
- 2023high 27 C, low 18 Cwater 23 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 Goseong 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
- 5:47:28
- Of the day on the bike
- 52%
- Dimensions scored per leg
- 12
- Season runway shown
- 24 wk
Questions people ask
- How hilly is the IRONMAN 70.3 Goseong run course?
- The organiser labels it hilly and describes the three-loop course as generally flat with one big steady hill, 500 m up and 500 m down at 7 percent. The file reads the steepest stretch at 153 m and 13.7 percent. The longest flat stretch is 22 percent of the run leg.
- What water temperature should I expect at Danghangpo?
- The organiser records 22 C in 2025, 25 C in 2024 and 23 C in 2023. The swim is one lap from a rolling pontoon start, in sea water the organiser describes as protected and surrounded by mountains.
- What are the cut-off times at IRONMAN 70.3 Goseong?
- The organiser sets them from each athlete's own swim start. The swim closes at 1 hour 10 minutes, the bike at 5 hours 30 minutes and the finish at 8 hours 30 minutes.
- How long is the season on this page?
- The illustrative season runs 24 weeks, with five developmental blocks and a two-week taper. It is built from the course alone. A member's season starts from their own numbers.
Course data from the organiser’s published files, analysed 25 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, and 5150 is a trademark, 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.