IRONMAN 70.3 · Mossel Bay · 22 Nov 2026
How to train for IRONMAN 70.3 Mossel Bay
The organiser calls this bike course hilly and puts a number on it, 1020 m of climbing on a single out-and-back from the beach to Uitkyk on the Herbertsdale road. Athletes read that line and spend their build grinding up long climbs. The climbs are real. They are just not where the day goes.
The file the organiser publishes measures 940 m, and the two biggest pieces of a Trained rider's 3:10:25 on the bike are both flat. One is the stretch on top of the first climb. The other is the long, gentle road home. What you did on the hills is paid for there, and then again on the run.
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
- Bike87.4 km940 m upCourse file
- Run21.2 km in 3 laps280 m upCourse file
You swim 1.9 km in the sea, point to point, from Santos Beach to De Bakke Beach, with the Outeniqua mountains across the bay and a rolling start for age groupers. The organiser logged the water at 20 C in 2025 and 19 C in 2024, puts the November average at 19.1 C, and leaves wetsuits optional. Out of the water you climb the beach, then a ramp, then a staircase, roughly 75 m in all to transition at the De Bakke beach parking area.
The bike leaves the sea and climbs at once. The first real rise, 2.3 km at 5.3 percent, starts inside the opening kilometre. Then 11.5 km of flat road, then a rolling stretch that rises in short steps to the high point near kilometre 28, some 330 m above the start. At kilometre 34 the road drops for 4 km at 5.3 percent into the low ground around the turn at Uitkyk. Coming back, the same slope climbs 4 km at 5.4 percent from kilometre 49. After that the rolling steps return, then 13.5 km of gradual downhill from kilometre 71, and a last 1.9 km plunge back to sea level. Three aid stations sit along the way.
The run is 3 laps through the harbour and the old town and out along the Point coastal walkway, on a mix of road and pedestrian pathway, with three aid stations on every lap. You leave T2 onto George Road. The file puts 280 m on it, yet the route never climbs much more than 20 m above where it starts. It is short rises of 200 to 350 m at 4 to 6 percent, repeated every lap, between flat pieces of up to 3 km.
Course shape by distance
- Flat 75%
- Climbing 13%
- Descending 12%
The longest stretches
- Bike, flat11.5 km12% of the bike
- Bike, flat13.5 km13% of the bike
- Run, climbing0.16 km1% 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 the bike, above everything, it asks for aerobic endurance at 85 and muscular endurance at 83, with threshold capacity at 70 and the two durability scores at 67. The bike is 53 percent of a Trained athlete's day, so the eight biggest demands in the cross-leg ranking are all bike demands. The run's pair reads 85 and 83. The swim's reads 85 and 80.
Two scores are particular to Mossel Bay. Environmental resilience reads 60 on every leg, and the weather explains it: the organiser logged highs of 30 C in 2023, 28 C in 2024 and 25 C in 2025. Technical skill reads 57 on the run against 40 on the bike. Three laps of harbour corners, old town streets and coastal pathway ask more of your running line than an open road asks of your bike handling.
High-intensity capacity reads 58 on the bike, and that comes from the rolling stretches on either side of the turn, where rises of a few hundred metres at 4 to 5 percent come one after another. Ask the engine for a session from this file and it builds twelve Zone 5 efforts of forty-five seconds, each followed by a little over four minutes of easy spinning. That is the rhythm of those stretches.
Put the bands against it. A Trained athlete swims 38:12, rides 3:10:25 at 182 W and runs 2:00:58, for 5:59:35. The Competitive band finishes in 5:10:40 from 4.15 W/kg at 75 kg and 4:20 /km threshold pace. That is more than 25 minutes quicker on the bike and 18 on the run, and very little of it comes from climbing harder. It comes from carrying a higher steady number over the flat and still having legs for the laps.
- 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
Every dimension above has a mirror on the athlete's side. Nymiva reads your thresholds and your connected training history into the same twelve scores the course gets, and marks each one with where it came from and how much weight it can bear. Where the course asks for more than you can show, you have a gap. Gaps are then ranked by the share of race day they touch, so on a course where the bike fills more than half the day, a small bike gap beats a large swim gap.
This page knows nothing about you. Its season therefore takes the plainest assumption, that your gaps sit where the demands are largest, and spreads 24 weeks over 5 developmental blocks before a two-week taper. Aerobic endurance leads the first block in all three sports. The second puts aerobic durability first on the bike and in the water and threshold durability first on the run. Threshold capacity leads the third, muscular endurance the fourth, and aerobic endurance returns to lead the last block before the taper. Your own season is built from your own numbers, and it will not match 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, 53% of the day85 × 53%45
- 02Muscular enduranceBike leg, 53% of the day83 × 53%44
- 03Threshold capacityBike leg, 53% of the day70 × 53%37
The bike takes 53% 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 Mossel Bay 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
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportBike aerobic durability
- SupportRun threshold durability
- SupportSwim aerobic durability
- Weeks 6 to 9Foundation 2Closes with a recovery week
- PriorityBike aerobic durability
- PriorityRun threshold durability
- PrioritySwim aerobic durability
- SupportBike aerobic endurance
- SupportRun aerobic endurance
- SupportSwim aerobic endurance
- SupportBike muscular endurance
- SupportRun 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
- SupportSwim aerobic endurance
- SupportBike muscular endurance
- SupportRun muscular endurance
- SupportSwim muscular endurance
- SupportBike aerobic durability
- SupportRun threshold durability
- SupportSwim aerobic 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
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportBike aerobic 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
- SupportBike muscular endurance
- SupportRun muscular endurance
- SupportSwim muscular endurance
- SupportBike threshold capacity
- SupportRun threshold capacity
- SupportSwim threshold capacity
- SupportBike aerobic 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
- 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
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, 4.3 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
- 81 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 | 0:45:05 | 3:32:37 | 2:25:28 | 6:53:10 |
| Trained1:51 /100m critical swim speed · 3.03 W/kg at 75 kg · 5:06 /km threshold pace | 0:38:12 | 3:10:25 | 2:00:58 | 5:59:35 |
| Competitive1:36 /100m critical swim speed · 4.15 W/kg at 75 kg · 4:20 /km threshold pace | 0:33:03 | 2:44:50 | 1:42:47 | 5:10:40 |
| Elite1:26 /100m critical swim speed · 5.27 W/kg at 75 kg · 3:50 /km threshold pace | 0:29:36 | 2:30:33 | 1:30:55 | 4:41:04 |
Pacing plan
- 0 km0.7%27.4 km/h0:38
- 0.29 km5.3%12.3 km/h11:04
- 2.57 km0.2%29.8 km/h23:09
- 14.1 km3.3%17.1 km/h0:45
- 14.3 km1%26 km/h9:23
- 18.4 km3.8%15.7 km/h1:13
- 18.7 km0.2%29.8 km/h6:29
- 21.9 km3.6%16.2 km/h1:14
63 more segments in the full plan.
- Run: reach 4:20 /km and this course gives back 48:55.
Where it is decided
Between kilometre 49 and the beach.
The turn at Uitkyk sits in low ground, so the way home starts with the longest continuous climb of the day, 4 km at 5.4 percent. It feels like the moment to race. It is the last big hill, the field has strung out, and the top looks close. A rider who goes over 182 W here gets a few seconds for it.
The bill arrives 18 km after the top. From kilometre 71 the road drifts downhill for 13.5 km at under half a percent, and the engine gives that single stretch 12.5 percent of the bike leg, the largest block of time in the whole race. It is too gentle to coast and too long to fake. A rider with power left in the legs gains time on every kilometre of it. One who emptied the tank on the climb sits up, watches the speed fall, and still has three laps to run.
Those laps settle the rest. The sharpest reading on the run, 8.7 percent over 161 m, falls on the third lap at kilometre 15, when every short rise costs more than it did the first time round.
Getting it wrong
The first mistake is made in the opening twenty minutes. You come out of the sea, climb 75 m of sand and stairs into transition, and within a kilometre of mounting the road climbs 2.3 km at 5.3 percent. Heart rate is already high and the climb invites you to ride it on adrenaline. Then comes 11.5 km of flat on top, 11.8 percent of the bike leg, where the right number feels too easy.
The descent into Uitkyk is the second trap. Four kilometres down at 5.3 percent is free speed, and it tempts you to press the flat run to the turn as well. Every metre of that descent comes back as climbing after kilometre 49, and the rider who spent on the way out meets it with nothing held back.
The third is the run in the heat. A Trained athlete starts it nearly four hours after the swim start, and 2023 reached 30 C. The long flat pieces along the water are where pace creeps up. The short rises on every lap are where it gets repaid. Run the rises at effort, not at your flat pace, and let the third lap be the fast one.
Conditions on the day
- 2025high 25 C, low 13 Cwater 20 C
- 2024high 28 C, low 17 Cwater 19 C
- 2023high 30 C, low 12 Cwater 22 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 Mossel Bay 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
- 5:59:35
- Of the day on the bike
- 53%
- Dimensions scored per leg
- 12
- Season runway shown
- 24 wk
Questions people ask
- How hilly is the IRONMAN 70.3 Mossel Bay bike course?
- Properly hilly. The organiser quotes 1020 m of climbing on one out-and-back from De Bakke to Uitkyk on the Herbertsdale road, and the file measures 940 m. Two long climbs carry most of it, 2.3 km at 5.3 percent inside the first kilometre and 4 km at 5.4 percent from kilometre 49 on the way home.
- What water temperature should I expect for the Mossel Bay swim?
- The organiser logged 20 C in 2025 and 19 C in 2024, and puts the November average at 19.1 C. Wetsuits are optional, decided by the water temperature. The swim is a sea swim from Santos Beach to De Bakke Beach.
- How many laps is the IRONMAN 70.3 Mossel Bay run?
- Three laps through the harbour and the old town of Mossel Bay and along the Point coastal walkway, with three aid stations on every lap. The surface mixes road with pedestrian pathway. The organiser quotes 365 m of climbing, the file measures 280 m.
- 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 own season starts from their numbers and can be longer.
Course data from the organiser’s published files, analysed 24 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.