"City-centre triathlon in Boulder — race through iconic streets and waterways."
🏊 Swim
Ocean swim in Boulder
🚴 Bike
Rolling bike course around Boulder
🏃 Run
Run through Boulder
Transition Details
T1/T2 are in the same location · Surface: pavement
Weather
Typical conditions in Boulder
Registration
https://www.example.com/boulder-triathlon-70-3
The Story
The half-iron distance asks a particular question: can you hold race pace for five-plus hours across three disciplines? In Boulder, the course adds its own follow-up questions. The 1.9km swim sends you into cool open ocean at 18°C — cool enough to want a wetsuit, warm enough to swim without panic. It's long enough that a poor start costs real time, short enough that strong swimmers can build a genuine lead. The 90km bike is the centrepiece: rolling with some honest climbs terrain with 517m of climbing that never lets you settle. At 70.3 distance, the bike is where races are won and lost — 90km of rolling road demands constant effort management. A rolling half-marathon through Boulder with 77m of gain. After 90km on the bike, even gentle rises feel significant. Quick cadence on the ups, controlled effort on the downs, and trust the training through the middle kilometres. This is 70.3 — the world's most popular triathlon distance, and this course shows why.
"The swim wakes you up, the bike breaks you down, and the half-marathon shows you who you really are. That's 70.3 in Boulder."
What It Feels Like
A half-iron course in Boulder that suits a broad range of 70.3 athletes — the course is honest enough to challenge veterans and achievable enough for well-prepared first-timers. The city's altitude training mecca turned race venue extends to the race itself. Recovery is part of the experience: a green smoothie and a microbrew.
🏊 The Swim
A 1.9km ocean swim in cool saltwater at 18°C — long enough that sighting discipline and stroke efficiency matter more than raw speed. Ocean swell can push you off-line; sight every 8-10 strokes. The salt buoyancy helps body position but stings the eyes. Exit through the surf and run to T1.
🚴 The Bike
90km of rolling terrain with 517m of climbing — the course signature. The rises are frequent enough to break any rhythm you try to establish. Over 90km, the cumulative elevation demands constant gear management and power discipline. Don't chase speed on the descents; recover there instead. This bike rewards riders who think in power, not pace.
🏃 The Run
A 21.1km rolling run through Boulder with 77m of gain. The undulations feel disproportionate on legs that have just covered 90km of bike. Keep cadence quick on the ups, use the downs to stretch your stride, and run the tangents. In mild 16°C conditions, each hill amplifies the heat cost. Walk an aid station if you need to — it costs 15 seconds and gains you proper hydration.
💡 Insider Tips
- → At 18°C, the water is cool enough to tighten your breathing on entry. Practice cold-water starts in training — jump in and swim 200m hard, then settle. The 1.9km swim is long enough that early panic costs minutes, not seconds.
- → With 517m of elevation over 90km of rolling terrain, the bike is deceptively demanding. The short rises don't look like much individually, but they accumulate. Stay in the aerobars on the flats, spin up the rises, and save your matches for the run.
- → Altitude changes everything at 70.3 distance. The 90km bike and half-marathon expose oxygen debt that shorter races can mask. Arrive at least 3-5 days early, ideally a week. Reduce target power and pace by 5-12% depending on elevation. Hydrate aggressively — you lose more water breathing dry, thin air than you realise.
Prepare for This Race
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FAQ
What distance is the Boulder Triathlon 70.3? +
The Boulder Triathlon 70.3 is a Half Ironman / 70.3 distance triathlon: 1900m swim, 90km bike, and 21.1km run (113km total) in Boulder, United States.
When is the Boulder Triathlon 70.3? +
Typically held in September on a Sunday.
Water temperature and wetsuit rules? +
Ocean water at 18°C average. Wetsuit rules are conditional.
How hilly is the bike course? +
517m of climbing over 90km. Profile: rolling. Drafting not allowed.
What's the weather like on race day? +
undefined–undefined°C, 39% humidity, 22% rain chance, 14 km/h winds.
Average finish time? +
Approximately 5h 30m. Varies with conditions and athlete experience.
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