Pacing & Predicting Your Half Marathon

Half Marathons are one of the most popular running distances. A half marathon at 21.1km or 13.1 miles presents a significant yet realistic challenge for runners of all abilities. 

For most, a half marathon will be completed between 1:30-2hrs at an intensity slightly below an individual’s anaerobic or lactate threshold (LTH). 

The target intensity (Pace, HR, Power) will be between 90-100% of your threshold. Where you sit within that zone will be dependent on many factors.  

Within my half marathon training sessions, I target 95 – 105% (zones 4-5) to push runners slightly harder than they will experience on race day and allow for the variances in fitness and experience levels. 

For those that have completed my “Half Marathon” prep sessions, you should be able to use the pace you held for the 5km or 10km sections of the session as your goal race pace/intensity.

In the example below, I have selected the second 5km to analyse this runner’s outputs. I can see their average power = 291W, pace = 4:27/min/km, HR = 155bpm. I would use these values as the targets for the race’s first half.  

If you slowed drastically in the 5km or 10km section of your Half Marathon Prep session, it means your outputs were set too high, and you need to start at a slower pace.