What happens after 100km

I'm no pro. I've only crossed 100km twice. But there are a few things I know for certain about what waits on the other side of it. Most of them, nobody warned me about.

First thing, and I mean actually sit with this rather than just nod at it: at 100km, pretty much everyone is in some sort of pain. Seriously I've asked them. I've heard elite Backyard Ultra runners say it plainly on podcasts. They hurt at that point. They've all struggled there.

This matters because if you go in thinking 100km is something you outlevel with fitness, you'll be blindsided. You won't outrun it. What you can do is be ready for it. Readiness starts with not being surprised.

The first 75km is actually easy

This is the part that catches people off guard. The first 70km, roughly the first 9 or 10 loops, goes by easily. Genuinely. It's fun. You're in a group, the hours tick over, the loop routine settles in. Around 50km you hit a rhythm and it feels almost meditative.

Nothing about that stretch prepares you for what follows.

Past 75km, then 100km, everything gets harder. You're slower. Your rest time shrinks because your legs are taking a little longer to turn over. The margins tighten. And the mental landscape changes completely.

Your weak spot

Muscle fatigue will be there. That's guaranteed. The question is where it shows up for you. Glutes, quads, calves, ITBs, ankles, lower back. Everyone has a spot that deteriorates faster than the rest. Know yours before race day.

Between loops, have your crew attend to it. Tight calves rubbed out. Quads worked. Foam rollers, massage guns, whatever helps. The small recovery work you do in those 10-minute tent windows compounds across 20 loops. I've heard of guys who do a squat at the end of each walking section just to stretch things out! An attended muscle is a muscle that keeps moving. An ignored one becomes the thing that ends your race.

The mind takes over

Past 100km, the mental game is your biggest challenge. Not your fitness. Not your nutrition. Your mind.

If you've never been past 100km in a race, you're now in territory you've never seen before. You're looking at loop numbers on your watch that you've never seen on a watch in your life. Your brain doesn't have a reference point. And a brain without a reference point starts looking for reasons to stop. It'll find them.

I can recall my last race clearly. I left at lap 16, around 107km. At that point I felt extraordinary. Genuinely excited, full of energy, giddy. I actually started thinking "I'm going to do 30 laps!"

Two hours later, at lap 18, everything changed. It got brutal. The hours I'd already run just landed on me all at once. From lap 16 to lap 18, two loops, two hours, my world completely changed. From there it was a downward slide and a fight to stay in the game.

Two loops. Two hours. That's how fast the shift can happen past 100km. My mind got the better of me and I can tell you when you finish you instantly regret it.

You can't wing the mental side of the back half. By the time you need it, it's too late to build it. Build it before race day. Go in with mantras, specific phrases and mental frameworks you've rehearsed, not ones you've invented on the spot at 3am when everything hurts. Honestly, speak to AI and develop a game plan. I did and it was great. I even printed some of the thinking and put it on the wall next to my chair. Work on the mindset side of your prep the same way you work on your long runs. There's good material in the Backyard Ultra community around this. Patto's Backyard Ultra Podcast is amazing. It gave me some of the most useful race prep I've done outside of actual running.

The physical challenge past 100km is real. But at that point, everyone still in the race is physically capable. What separates who keeps going is what's happening between the ears.