How to Pace an IRONMAN 70.3 (Half Distance Triathlon) for a Strong Race

A solid pacing strategy can make or break your 70.3 race. Stick to your limits, follow your plan, and avoid over-exerting early — it’s often better to finish strong than fade and struggle.

Swim — Start Smart, Stay Controlled

The 1.9 km (1.2-mile) swim begins the race — but it should only use a sustainable portion of your energy. 

• The first 300m may feel intense; settle into a steady rhythm right after that.

• Use drafting if you can: swim behind or beside another swimmer to save energy. 

• Focus on consistent, efficient technique; avoid tension or sprinting early. 

Avoid these common mistakes:

• Going out too hard — this can sap energy needed for the bike and run. 

• Following the wrong swimmer - who’s not swimming the best course or not a good pace match. 

• Not staying relaxed — stay smooth. 

Bike — Ride Steady, Protect Your Run

The bike leg (90 km / 56 miles) is probably the most important part of your pacing strategy. Pacing it smartly sets up a better run. 

• Use a power meter if possible. This gives the most precise control. 

• If you don’t have a power meter, monitor heart rate and perceived effort (RPE). 

• Keep effort consistent — avoid surges, spikes or “bonk” efforts, especially on hills. 

• Don’t chase other riders who push hard early. Let them waste energy while you stay steady and strong for later. 

• Follow your fueling and hydration plan strictly — a steady bike pace helps your body digest nutrition, setting you up for a better run. 

Common bike-pacing mistakes to avoid:

• Going too hard early — risks killing your legs and compromising the run. 

• Over-pushing on climbs — stick to your sustainable effort. 

• Ignoring nutrition and hydration — underfuel or dehydration often wreck the run.

Run — Start Conservatively, Finish Strong

By the time you start the 21.1 km run, you’ll be fatigued. The run isn’t a standalone half-marathon: treat it according to your remaining energy, not how you feel in isolation. 

• Begin at an easy, controlled pace — likely similar to, or slightly slower than, your full-marathon pace. 

• Use a combination of RPE, heart-rate, and pace to guide your run — don’t rely on just one. Conditions (wind, hills, fatigue) affect each. 

• If you feel good halfway (around 10–12 km), you can gradually increase pace. Otherwise, steady pacing avoids bonking.

• At aid stations — walk briefly if needed to hydrate or eat, but keep moving forward. Guard against killing momentum by stopping too long. 

• Be prepared mentally: break the run into manageable chunks, use positive self-talk, and stick to your plan. 

Use Real Data — Don’t Guess

Pacing works best when it’s based on recent fitness tests (power, heart-rate, pace thresholds) — not on guesswork or wishful thinking. 

A good tool to help with this is the MyProCoach Triathlon Race Pace Calculator, which can set realistic race-day targets based on your fitness level. 

Final Advice — Race Smart

• Swim steady and controlled. 

• Bike with patience and discipline. 

• Run sensibly — start cautiously, stay consistent. 

Stick to your pacing plan, trust your training, and stay disciplined. Over a 70.3, pacing right is often what makes the difference between finishing strong — or just finishing.