It’s nice when a goal race is on flat, normal terrain. A place like Chicago or New York City makes it easy, since all their races are on mostly flat ground.
Along with creating prime conditions for fast times (… well, weather permitting), training for the races is straightforward. Work on aerobic and neuromuscular fitness, work on tempo and speed, recover and feed yourself well, and you can crush it.
If a race has elevation shifts, things get a bit more complicated. We already see how weather and temperature impact races: If you train in clear and mild conditions, but then race in windy, hot/cold conditions, you’re not going to be trained to deal with the latter. Even when trained for warmer conditions, suitably hot races can negatively impact performance no matter what.
Likewise, if you train on flat ground, then try to run a race with hills (whether uphills or downhills or both), your performance and body will suffer as you likely have not trained at any length to handle hilly conditions. The longer the race, the greater the impact.
Runners who live in hilly locales face challenges with training speed, tempo or maximizing mileage because of the hills impacting speed. But this becomes an advantage when they run races featuring hills. Their bodies are well-trained to deal with the big elevation shifts. American runners in Seattle, Cincinnati, Pittsburgh and mountainous regions like Colorado and Utah are better equipped to handle hills than runners in Chicago, Florida or New York City. (Plus, that never minds thinner air in higher altitude, also a key factor and a separate subject)
So, as a Chicago runner, I have to be mindful when I blow town for a race in a locale with hills. Vancouver is a clear example, with not only big elevation shifts early in the Vancouver Marathon course, but even the smaller elevation shifts later in the race are mountainous compared to the elevation changes in flatter Chicago.
One key reason these hills didn’t destroy me is that on multiple occasions I ran special workouts at nearby Cricket Hill. While Cricket Hill isn’t exactly a big hill (with only a 45 foot elevation climb), it does rise at a tough grade and when run on right, it can prepare you for running up and down hills.