Today I'm going to show you exactly how I'd prepare a beginner for their first triathlon with 90 days to go.
Whether you're aiming for a sprint triathlon or a short-course event, this simple plan will help you arrive at the start line confident, fit and injury-free.
No fancy gear. No complicated science. Just a sensible structure that works.
The Big Mistake Beginners Make
Most beginners fall into the same traps:
- Train too hard, too often
- Do random workouts with no plan
- Don't allow enough recovery
- Focus on one discipline and neglect the others
Here's the truth: the goal isn't to smash yourself.
The goal is to arrive at race day healthy and consistent. Fitness comes from showing up regularly over weeks and months — not from a handful of heroic sessions that leave you injured or burnt out.
Break The 90 Days Into 3 Blocks
The simplest way to structure your build is to split it into three 30-day blocks. Each block has a clear job to do.
Block 1: Foundation (Days 1–30)
Goal: Build consistency.
Focus:
- Easy aerobic training
- Technique in all three disciplines
- Developing a routine you can stick to
Training effort: 80–90% easy.
"At this stage we're building the engine, not testing it."
Block 2: Build Phase (Days 31–60)
Goal: Increase endurance and confidence.
Focus:
- Slightly longer sessions
- Introduction of some race-pace efforts
- Your first brick sessions
Example brick: Bike 45 minutes + Run 10 minutes, straight off the bike. This teaches your legs what it feels like to run on "jelly legs" — an essential skill for race day.
Block 3: Race Preparation (Days 61–90)
Goal: Prepare specifically for race day.
Focus:
- Race-pace work
- Open water practice
- Transitions (T1 and T2)
- Nutrition rehearsal
- Confidence
Golden rule: nothing new on race day. Practise exactly what you'll do when it counts — the same breakfast, the same gels, the same wetsuit, the same warm-up.
The Importance Of Periodisation
Here's the concept that ties the whole plan together. Rather than adding load every single week until you break, you build in waves.
3 weeks build, 1 week recovery.
Each build week you make a small increase in volume and duration:
| Week | Weekly Volume |
|---|---|
| Week 1 | 5 hours |
| Week 2 | 6 hours |
| Week 3 | 7 hours |
| Week 4 | Recovery — reduce volume by 30–40% |
The benefits of training this way are enormous:
- Better adaptation
- Reduced injury risk
- Better long-term progress
"Fitness isn't built during training. Fitness is built when your body recovers from training."
Want to go deeper on this? I've put together a full training periodisation guide that explains exactly how to structure your build, base and peak phases.
Weekly Training Structure
Here's a simple week that covers all three disciplines without overloading you. Nine key sessions — three swims, three bikes, three runs — plus recovery and mobility.
| Day | Sessions |
|---|---|
| Monday | Recovery / Mobility |
| Tuesday | 🏊 Swim + 🚴 Bike |
| Wednesday | 🏃 Run + Strength / Mobility |
| Thursday | 🏊 Swim + 🚴 Bike |
| Friday | 🏃 Run + Recovery |
| Saturday | 🚴 Long Bike + 🏃 Short Brick Run |
| Sunday | 🏊 Swim + 🏃 Long Run |
What Each Discipline Is For
Swim — 3 sessions
- Technique
- Endurance
- Confidence in open water
Bike — 3 sessions
- Aerobic fitness
- Endurance
- Strength
Run — 3 sessions
- Consistency
- Injury prevention
- Gradual progression
Swimming is where most beginners lose the most time and confidence, so treat those technique sessions as non-negotiable. The bike is where you'll build most of your aerobic fitness, and the run is where you need to be most patient — progress slowly to keep your legs healthy.
Final Week (Race Week)
The temptation in the last week is to cram in extra fitness. Don't.
- Reduce your volume significantly
- Keep some short, sharp intensity to stay sharp
- Prioritise sleep, hydration and nutrition
- Stay fresh
The work is already done. You can't gain fitness in the final week — but you can absolutely lose freshness by trying to. Trust your training and arrive rested.
When you're packing your bag, my race day checklist will make sure nothing gets left behind.
Putting It All Together
If you've got 90 days until your first triathlon, remember this: consistency beats perfection.
Three swims, three bikes and three runs each week, structured into sensible training blocks with regular recovery, will get you to the start line ready to enjoy the experience.
Don't chase the perfect week. Chase the consistent month.
Want A Plan Built Around You?
This is the framework I'd start any beginner with — but the best results come when a plan is tailored to your fitness, your schedule and your race.
If you'd like me to take a look at your training, I offer a free 30-minute training review. We'll talk through your goal race, where you're at now, and how to structure your build.
You can also grab my free 8-week sprint training plan to get started today, or explore all my free resources for beginners.
Let me know in the comments what race you're training for and how many days you've got until race day. I read every one.