The short answer
You probably overbiked your 70.3 if two or more of these are true: your bike power sat above a level you have genuinely sustained before, your power in the second half dropped more than about 5% below the first, your heart rate kept climbing late while power flattened or faded, and your run started near target pace then decayed through the first few kilometres. One of those alone is weak evidence. Three pointing the same way is close to a verdict.
A run that was flat and slow from the gun is a different story — that points at run pacing, fuelling or fitness rather than the bike.
The numbers we actually use
These are the thresholds The Debrief applies to a 70.3 bike leg, so you can check them against your own file whether or not you ever upload it:
- Intensity factor 0.75–0.80 is the target band for a half. At 0.82 and above we treat the ride as an overbike; 0.72 and below reads as leaving time out there.
- Variability index at or under 1.05 is a smoothly ridden bike. Past 1.08 the surging itself is costing you, whatever the average says.
- Power-to-heart-rate drift under 5% is normal. Over 10% is the decoupling that marks an effort which ran past what you could hold.
- Second-half fade under 3% is fine. Over 5% is significant.
- On the run, a first-half/second-half split within 2% is excellent execution and within 5% is acceptable. An opener more than 5% faster than your eventual average is a hot start.
Full-distance racing uses a different set — the IF band drops to 0.68–0.73 and the drift and fade tolerances roughly double, because a five-to-six hour ride behaves differently from a two-and-a-half hour one. Those are on the IRONMAN version of this page.
Why the IF number alone will mislead you
Intensity factor is only as good as the FTP underneath it, and a lot of age-groupers are working off a figure that is stale or was never properly tested. A high IF against a wrong FTP tells you nothing at all. This is the single most common way a self-diagnosis goes wrong, and it is why the first bullet above is about demonstrated power rather than a percentage.
The comparison that holds up is against power you have genuinely sustained before, in a race or a long hard session. If your race sat well above that, you went too deep. If it sat at or below it, the run problem probably lives somewhere else.
What The Debrief checks
- Whether your bike power sat above a level you have demonstrably sustained, not an estimated ceiling you never touched.
- How your power held or faded across the second half, where overbiking usually shows first.
- Whether your run pace decayed in the pattern that follows a bike that was too hard, versus heat, fuelling or a pacing error on the run itself.
- How your heart rate tracked your power, since decoupling late in the bike is one of the clearer tells.
If the file cannot support the verdict, it will say so. Calling an overbike you did not commit is worse than leaving the question open. The read stays inside what your data can actually prove.
No power meter? This still works
Three of the four signals above do not need watts. Second-half fade shows up in speed on a comparable course, heart-rate drift needs only a strap, and the run-decay pattern is pure pace. A file with heart rate and GPS and no power will still get you a read — it will just be stated with less certainty on the bike leg, and the report will say so rather than quietly pretending otherwise.
What you get back
A debrief written the way a coach would talk you through it. Not a wall of charts to interpret yourself, and not a confident verdict pulled out of thin air. Just what the file shows about how you executed, in plain language, on screen, right after you upload. Here is a full sample on a real 9:12:22 race file if you want to see the output before handing over anything of your own.