Your first triathlon build

A sprint triathlon — typically a 750 m swim, 20 km bike and 5 km run — is one of the most achievable "big" endurance goals there is. You don't need to be fast at any of the three sports. You need to be adequate at all of them on the same morning. That changes how you should train.

The ground rules

• Train your weakest sport most. For most first-timers that's the swim. Comfort in open water is the single biggest gap between finishing relaxed and panicking at the first buoy.
• Frequency beats heroics. Five or six short sessions a week beat three monster ones. Each sport needs regular touches to build skill, not just fitness.
• Almost everything is easy pace. Conversational effort builds the aerobic base that carries all three sports. Save hard efforts for one or two sessions a week, and only after the first month.

A workable week on roughly five to six hours: two swims, two bikes, two runs, with one full rest day. Shift the balance toward whichever sport scares you most.

Weeks 1–4: base

The only goal is frequency and comfort.

• Swim: technique-first. Short repeats (e.g. 8–12 × 50 m) with generous rest, focusing on breathing rhythm and a long, relaxed stroke. Drills beat distance.
• Bike: two easy rides, building one toward 45–60 minutes. Learn your gears and practice drinking while riding — genuinely a skill.
• Run: two easy runs of 20–30 minutes. If you're newer to running, use walk breaks without guilt.

Hold every session easy enough that you finish feeling like you could do more. That restraint is the training.

Weeks 5–8: build

Volume creeps up (~10% a week), and structure appears.

• Swim: extend repeats toward 100–200 m and start one continuous swim per week, building toward 750 m without stopping. If the race is open water, get at least two open-water sessions in this block — sighting and swimming straight are learned skills.
• Bike: one ride gains short pickups (e.g. 4 × 3 min at a comfortably hard effort); the long ride builds to 75–90 minutes.
• Run: one run gains strides or short tempo segments; the other stays easy.
• Bricks begin. Once a week, run 10–15 minutes immediately after a bike. The jelly-legs feeling off the bike is universal and it fades with practice — race day should not be the first time you meet it.

Weeks 9–11: sharpen

Make pieces of training look like the race.

• One swim per week at target race effort, in the wetsuit if you'll wear one.
• One bike-to-run brick at race effort for part of the session.
• One full dress rehearsal around week 10: a mini-triathlon at perhaps half race distance, practicing transitions — helmet on before touching the bike, laces already elastic, nutrition where you can grab it.

Keep total volume flat here. The gains now come from specificity, not more hours.

Week 12: race week

Cut volume roughly in half but keep small doses of intensity early in the week — a few pickups keep you sharp. Then the unglamorous essentials:

1. Nothing new on race day: no new gear, food, or pacing plan.
2. Rack your gear in the order you'll use it and walk the transition area.
3. Seed yourself honestly in the swim start and begin slower than feels right.
4. Pace the bike so you can still run — your 5 k off the bike should start easy.

The honest takeaway

First-triathlon training is mostly about removing unknowns: the open water, the brick legs, the transitions. Fitness gets you to the course; familiarity gets you to the finish smiling. Twelve weeks of consistent, mostly-easy training across three sports is enough for almost anyone starting with basic swim and run ability.

Ugoku can plan multi-discipline weeks like these with paces and zones from your own benchmarks — or take this skeleton and fill it in yourself. Either way: see you at the start line.