One of the most common mistakes I see in Ironman 70.3 racing happens within minutes of athletes leaving transition.
They start the run too fast.
The strange part is that it often feels completely right at the time.
After all, you’ve just finished the bike. The crowd is cheering. The finish line suddenly feels achievable. Your legs have finally stopped turning pedals and you’re excited to get running.
Unfortunately, what feels easy in the first kilometre is often anything but sustainable.
Why the First Kilometre Can Be Misleading
When you begin the run in an Ironman 70.3, your body is coming off 90 kilometres of cycling.
Your heart rate is elevated.
Your muscles are already carrying fatigue.
Your glycogen stores have been steadily depleted.
Yet many athletes report that the first kilometre feels surprisingly comfortable.
This is where trouble begins.
The combination of race-day adrenaline and the transition from cycling to running often makes your pace feel easier than it actually is. You look at your watch and discover you’re running significantly faster than planned.
At the time, it feels manageable.
Ten kilometres later, it doesn’t.
The Cost of Starting Too Fast
The problem with running too hard early isn’t necessarily what happens in the first few kilometres.
The problem is what happens in the final few kilometres.
A pace that’s only slightly too aggressive can dramatically increase your energy expenditure. Heart rate drifts upward, muscles accumulate fatigue faster, and nutrition becomes harder to process.
The result is often a steady slowdown over the second half of the run.
You’ve probably seen it yourself.
Athletes who fly past you leaving T2 are often the same athletes you’re passing later in the race.
Ironman 70.3 rewards patience.
What Should the First 2km Feel Like?
For most athletes, the first 2km should feel almost disappointingly easy.
You should feel like you’re holding back.
You should feel like you could comfortably run faster.
You should feel slightly frustrated by how conservative you’re being.
That’s usually a sign you’re doing it correctly.
Use those opening kilometres to:
- Settle your breathing.
- Find your running rhythm.
- Establish good posture.
- Take on nutrition if required.
- Let your heart rate stabilise.
Remember, you’re not trying to win the first 2km.
You’re trying to run your fastest possible half marathon after a swim and bike.
Focus on Effort, Not Pace
One challenge on race day is that pace can be affected by wind, terrain, temperature, and course conditions.
That’s why I encourage athletes to pay close attention to effort.
Ask yourself:
- Can I maintain this effort for another 15km?
- Is my breathing controlled?
- Am I running smoothly?
- Does this feel sustainable?
If the answer is no, you’re probably going too hard.
The athletes who execute the best Ironman 70.3 runs aren’t necessarily the fastest runners on paper.
They’re the athletes who manage their effort most effectively.
The Strong Finish Strategy
The best Ironman 70.3 runs often look remarkably similar.
The athlete starts conservatively.
They settle into a sustainable rhythm.
They maintain control through the middle stages.
Then, if they’ve paced correctly, they begin passing people over the final third of the run.
That’s a much more enjoyable experience than spending the last 5km trying to survive.
Instead of asking yourself, “How fast can I run right now?“
Ask yourself, “How fast can I run for the next 21.1km?“
That simple shift in mindset can transform your race.
Final Thoughts
A successful Ironman 70.3 run is rarely determined by how fast you start.
It’s determined by how well you finish.
The next time you race, give yourself permission to be patient.
Hold back for the first 2km.
Trust the process.
Trust your training.
Because if your first 2km feels a little too easy, there’s a good chance you’re pacing it exactly right.
Ready to Run Your Best Ironman 70.3?
Whether you’re training for your first Ironman 70.3 or chasing a new personal best, having the right plan can make all the difference.
If you’d like help with your training, race pacing, nutrition strategy, or overall race preparation, I’d love to learn more about your goals and see if I can help.
Book a free, no-obligation coaching consultation and let’s chat about where you are now, where you’d like to get to, and the best path forward.
There’s no pressure and no hard sell—just an opportunity to discuss your goals with an experienced endurance coach and walk away with some practical next steps for your training.