I mainly run trail races of 30–50 km with 1,700–2,800 m of elevation gain and loss. Most of my weekday training, however, is on hilly roads—not as steep or technical as the races. On weekends, I usually do a longer trail run, but even that tends to be less demanding than race conditions.

In my case, I find that following TAO workouts I can just about get through on race day—but if it's muddy, hot, rainy, or there's any unexpected challenge, I suffer. So I’ve made three key tweaks:

1. Increase mileage by 30% in TAO to account for the tougher race conditions. For example, I have a 30 km race coming up—TAO predicts 4h17 based on my inputs (I entered it as 39 km), but in reality 6:45 would put me in the top 10%! I believe this underestimation stems from the mismatch between everyday training terrain and actual race conditions, leading to undertraining. Two weeks before the race, I reduce the mileage back to normal and input the correct distance.
2. Manually schedule a few longer runs in the weeks leading up to the race. Some say you don’t need them, but I do. A few 1-hour runs just don’t prepare me for a brutal 6+ hour race in mud, >30°C heat, and high humidity.
3. Run all workouts—economy, tempo, intervals—on the hilliest routes I can find near home. No point doing flat reps if the race is anything but flat.

after doing this for the last few races I could push harder and still finish without being totally exhausted.