How 100 Mile Races Work: A Crew's Guide¶
You start, usually early in the morning, and keep moving through the night and into the next day. Aid stations every few miles have food and a cutoff time. Most races let crew meet you at some of them, and many let a pacer join for the later miles.
This post fills that in for the person who is not running: the partner, parent, friend or sibling who said yes to crewing and is now wondering what happens at 2am.
The same outline holds for a 50K, a 100K or a first hundred. The hours just stretch.
What actually happens, start to finish¶
Western States, one of the oldest and best known, starts at 5am and gives runners 30 hours to finish, so the clock runs out at 11am the next day (The Running Channel). Other races start at 6am, at noon, or at night. Time limits differ too. The race's own runner guide is the only place the real numbers live.
Here is the day in order.
Morning. The runner starts fresh and goes slower than feels right. Everyone does. The early miles are about not spending anything.
Afternoon. Hours of running, walking the climbs, eating on a schedule. Aid stations come every few miles. Each one has water, food, and volunteers who will fill a bottle and send the runner back out.
Evening and night. The headlamp comes out. The hours between dark and sunrise are the long middle of the race. The runner is slower, colder, and often low on energy and mood. This is the part nobody can explain until they have been in it, and it is the part crew matters most.
Next morning. The sun comes up and most people find a second wind. The last miles are slow, and then they are done.
A good crew keeps no scoreboard. A long slow day on the course is a big day, and the finish is the point.
How many 100 mile races are there?¶
I do not have one official count, so here is the number I can stand behind: NavRun's race catalog.
The catalog lists 71 hundred-mile course entries. Of those, 60 allow crew and 54 allow pacers. The rest are unknown or no. (Read-only query on NavRun's production race catalog, run 2026-10-02.)
Most of them allow crew, and fewer allow pacers. "Unknown" is a real answer there: some races have not published the rule, and the catalog says so rather than guess. If your race is one of them, ask the race director before you plan around it.
Do you sleep during a 100 mile race?¶
Plenty of runners never lie down. With a 30-hour limit like Western States, the night is unavoidable, but a bed is not part of the plan for everyone.
Some runners take a short nap at an aid station or in the car. Some sit for ten minutes and get up. What you will see as crew is a runner who is tired in a way they have not been before, and who may be quiet, slow to answer, or a little off.
Two things for you to do:
- Ask the runner what they decided before the race. A plan made in daylight is easier to follow at 3am.
- If they are weaving, confused or cannot keep food down, tell an aid station medic. That is not a call for you or the runner to make alone, and a medical professional is the right person to decide.
We wrote a longer piece on this: Sleep and naps in a 100.
What do crew and pacers do?¶
Your crew meet the runner at the aid stations where the race allows it. You are not racing. You are the person with the right thing in the right bag.
Most of the job is arithmetic and waiting. You drive to the spots the race lets you in, you have the food, the dry socks, the headlamp batteries and the warm layer ready, and you get the runner in and out. The faster you get through the stop, the better, and the less you talk about the numbers, the better.
Pacers run or walk with the runner for part of the course. Many races only allow them after a point. At Western States, for example, every runner may have one pacer from mile 62 (Foresthill) on (The Running Channel). A pacer carries nothing for the runner to think about. They watch the footing, keep the conversation going, and keep the runner eating.
The full checklist, the bags and the night-time rules are in our crew and pacer guide. Read your race's crew rules first. They decide which aid stations you can reach and what you can hand over.
What happens if you miss a cutoff?¶
Each aid station has a cutoff: the latest time a runner can arrive. If a runner arrives after it, the race usually ends for them at that station. Rules vary, so check the race's runner guide for how yours handles it.
A cutoff is a time on a clock, not a verdict on the runner.
For crew, the useful thing is to know the cutoffs ahead of time and to keep that arithmetic off the runner's mind. If you can see they are close, say what you know in a calm voice: "You have two hours to the next one, and that is fine."
We broke down the numbers for two races: Leadville 100 cutoff math and every aid station cutoff.
The hours you cannot be there¶
There is a stretch where crew cannot reach the runner. The course goes into places cars cannot, or the race does not allow crew until a certain mile, and phones have no signal for hours.
On his first 100 attempt, people sent Ike voice messages and he listened to their encouragement in his headphones. As he put it: "You can't read and text while you're doing it, but listening to people's encouragement in your headphones, it was like so powerful." That is when he thought he could build it into the app, and then that if a crew can talk to the runner, they know what the runner needs at the next aid station.
That became Out Here. The runner sends one link before the start. You open it in a browser, see where their phone last reported and how old that report is, and record a voice message. It lands on their phone the next time they have signal, and they hear it without reading. You do not need the app or an account, and it is free. It is not a safety device, and nobody should carry it as one. It will not take the night away. It means the night is not silent.
What to do this week¶
- Find the runner's race page and read the crew rules and the cutoffs.
- Ask what they want to hear at mile 60, and what they do not.
- Write down the aid stations you can reach, with times.
- Decide who sends the link to family and friends, and when.
Nobody is out there alone. Not the runner, and not you at the aid station.