Key takeaways
- A pacer is a runner who joins an ultrarunner for part of a race to support and motivate them.
- They help with company, motivation, navigation, pacing, and safety — especially at night and in late stages.
- Race rules vary: pacers generally can't physically aid the runner (e.g., carrying their gear) where 'muling' is banned.
- Pacers run with the racer on-trail; crew support the racer at aid stations from off-trail.
What a pacer is
A pacer is a runner who accompanies an ultramarathon racer for part of a race — usually the later, hardest stages — to provide company, motivation, navigation help, and a safety presence. As fatigue mounts over long trail ultras, a pacer keeps the runner moving, focused, and safe, which is especially valuable through the night.
What pacers do (and don’t)
- Motivate and keep the runner moving through low points and bonks.
- Help with navigation and pacing on remote trails.
- Provide safety — a second person in case of trouble.
- Cannot usually physically aid the runner — carrying their gear (‘muling’) is often banned.
At mile 60 of a 100-miler, a depleted runner picks up their pacer at an aid station; the pacer runs the final overnight miles with them — chatting, watching the trail markers, and pushing them to keep eating — without carrying any of their gear, per the race rules.
Pacer vs crew
A pacer runs with the racer on-trail; a crew supports them from off-trail at aid stations with food, gear, and care. See crew vs pacer. Always check each race’s specific pacer rules, as they vary widely.
The bottom line
A pacer is an ultrarunner's on-trail companion through the hardest, often darkest miles — providing motivation, navigation, safety, and steady company when the racer is depleted. Within each race's rules (which often bar physically aiding the runner), a good pacer can be the difference between finishing and quitting. They complement crew, who support from the aid stations.
Frequently asked questions
What does a pacer do in an ultramarathon?
A pacer runs alongside an ultramarathon racer for a portion of the event — usually the later, hardest miles — providing companionship, motivation, help with navigation and pacing, and a safety presence (important on remote trails and overnight). They keep the runner moving, focused, and safe when fatigue sets in.
What are the rules for pacers?
Rules vary by race, but pacers are typically only allowed after a certain point in the course, must be entered/registered, and generally cannot physically assist the runner — for example, carrying their pack or gear ('muling') is often prohibited. Some races don't allow pacers at all. Always check the specific event's rules.
What's the difference between a pacer and crew?
A pacer runs with the racer on the trail; a crew is a support team that meets the racer at designated aid stations or access points to provide food, gear, and care, but doesn't run with them. Crew support from the sidelines; pacers accompany on the move. See our crew vs pacer comparison.
Sources
- Ultramarathon racing — American Trail Running Association
- Endurance events — American Council on Exercise