To Bone and Back Relay
About this race
This 40 mile relay has been around in Southeast Idaho for 34 years now. Join today and run with a team of 8 (each person running 5 miles), a team of 4 (10 miles each), a team of 2 (20 miles each) or if you are feeling adventurous run the whole 40 miles!!! Come out with friends and/or family to enjoy a great event and great prizes!
Pick your distance
Trail running
40-Mile Solo
We'll be honest, this is a TOUGH Ultra-Marathon. Our course is 100% on asphalt road and is very hilly!
Running
2-Person Relay
This is a two-person relay! You can divide up the mileage in any way you would like. However, you can only exchange runners at our 5-mile aid stations. We have seen teams switch every five miles, every 10 miles, at halfway, or we've had some do 5,10,10,10,5. It is ultimately up to you and your teammate on how you'd like to divide this up.
4-Person Relay
This is a four-person relay! You can divide up the mileage in any way you would like. However, you can only exchange runners at our 5-mile aid stations. The most common is to have every teammate run 10 miles then switch; however, we have seen this broken up in a variety of ways as well.
8-Person Women's Relay
This is an eight-person women's relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles. (If you only have 1 male, you are part of the Women's Relay, not the Co-ed Relay.)
8-Person Men's Relay
This is an eight-person men's relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles. (If you only have 1 female, you are part of the Men's Relay, not the Co-ed Relay.)
8-Person Coed Relay
This is an eight-person women's relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles. (You must have two males or two females to be considered a Co-ed Team, if you only have one male, you need to register for the Women's Relay, if you only have one female you need to register for the Men's Relay.)
8-Person Family Relay
This is an eight-person Family relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles. All teammates must be related in one way or another.
8-Person High School Girls Relay
This is an eight-person HS Girls relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles.
8-Person High School Boys Relay
This is an eight-person HS Boys relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles.
8-Person High School Coed Relay
This is an eight-person HS Coed relay! Each teammate must run 5 miles! You cannot switch runners in the middle of a leg. It is okay, however, to only have 5 to 7 runners if you are unable to make a complete team. That just means that a few of your teammates will be running 10 or more miles. (Having just 1 girl does not qualify for a Coed, you'd be in the HS Boys Division.)
5-Mile Solo
This event is open to anyone who could not find a team, or cannot spend the day being with a team.
Typical race-day weather
Based on 1 year of Open-Meteo archive data for this event's race dates in Idaho Falls, plus the 3 days either side.
The sun rises at 5:49 AM and sets at 9:13 PM local time (MDT) in Idaho Falls on June 27, 2026 — 15h 24m of daylight.
Course
No course map published yet.
The organizer hasn't released a route for this event, and we don't publish guesses. If you're the organizer, send us a GPX file and we'll draw the profile.
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Other races near Idaho Falls
Different organizers, within 40 miles, in the next three months
🏃 Plan Your Next Race in Idaho Falls
Find upcoming events by distance:
- Idaho Falls 5K Races 11 races
- 10K Run Events in Idaho Falls 3 races
- Idaho Falls Running Calendar 2026 13 races
Where this page comes from. Race details were last updated on . We re-check listings regularly and again in the week before race day.
- Entries, prices, waves and inclusions — the event's official registration page
- Temperature and humidity — Copernicus ERA5 reanalysis via Open-Meteo (CC BY 4.0)
- Elevation and terrain relief — Copernicus DEM GLO-90, ESA (CC BY 4.0)
- Comparisons and counts — Race Discovery calendar, 13 Idaho Falls events
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