IRONMAN 70.3 Triathlon

So you’re thinking about taking on a 70.3. Also known as a Half Ironman, it’s no small thing: 1.2 miles of swimming, 56 miles on the bike, and a 13.1 mile run to finish. And yet, for a lot of people, it’s just right — big enough to challenge you, but achievable with consistency.

This blog is for the person who’s not starting from zero, but isn’t exactly racing every weekend either. You might know how to swim, own a bike, and have run a few 5Ks or half marathons. Maybe you’ve never done a triathlon before. Or maybe you’ve tried a sprint or Olympic and you’re ready to go further.

Wherever you’re coming from, this is your guide to training for a 70.3 in 12 weeks.

What to Expect from the Distance

A 70.3 will test you. But you don’t have to be superhuman. You just have to be prepared. Expect to train 6 days a week, with a mix of swimming, biking, running, and rest. Most sessions are manageable (45–60 minutes), with longer rides and runs on weekends.

You don’t need fancy gear. You don’t need a coach. You do need a plan, a willingness to learn, and some patience with your legs.

Your Starting Strengths (and What to Work On)

If you can already:

• Swim a few lengths comfortably

• Ride a bike for 60 minutes

• Run a 10K (or have done it before)

… then you have a solid foundation. The goal now is to build endurance, practice transitioning between sports, and get your body used to doing all three in succession.

Don’t worry if you’re stronger in one discipline than the others. Everyone is. The key is to train your weakness, maintain your strength.

The 12-Week Structure (Simple and Realistic)

Here’s a rough weekly framework:

• Monday – REST (let your body recover)

• Tuesday – Run (intervals or steady)

• Wednesday – Swim (technique or distance)

• Thursday – Bike (intermediate ride or indoor trainer)

• Friday – Swim + short run (brick session)

• Saturday – Long bike ride (builds aerobic base)

• Sunday – Long run (steady pace, focus on time on feet)

Include 1 or 2 short strength/core sessions a week if you can, especially in the first 6 weeks.

Every 4th week, reduce volume by 20% to allow for recovery.

Brick Sessions & Transitions

A “brick” means doing two disciplines back-to-back, like biking then running. It helps train your legs to deal with the shift in movement. At least once a week, simulate this. You don’t need to go far — a 40-minute ride followed by a 15-minute jog is great.

Practice transitions too. Lay your gear out. Time yourself. Get comfortable moving from swim to bike and bike to run.

Race Prep Basics

• Get familiar with race-day nutrition: Practice eating and drinking during long rides and runs.

• Do a gear check 2 weeks out: Ensure your bike is in good condition and everything fits comfortably.

• Train in the kit you’ll race in: Avoid surprises. Chafing at mile 40 is not fun.

• Taper in the final 10 days: Reduce volume but maintain light intensity.

Final Thoughts

Training for a 70.3 isn’t easy. But it’s massively rewarding. You’ll learn a lot about yourself, your limits, and what you’re capable of. You’ll have tough days. You’ll have big wins. And if you stay curious through it all, you might just surprise yourself.

Start where you are. Use what you have. And if in doubt, just keep moving forward.

More to Come

This post is part of my How to Be Curious series. The 70.3 was my first challenge in a year of trying 50 different things.

Follow along on Instagram [@iamalanrose] or tag me in your own training using #howtobecurious.