TNF Endurance Challenge: DC 50 Miler Race Info




Algonkian Regional Park

Sterling, VA

Avg Temps f.


Gain/Loss in ft


92 ft/mile gain

Highest Elev.

374 ft




Mainly trail

Time Limit

13 hours



Furthest Aid

4.8 miles

Summary: Starting and Finishing at Algonkian Regional Park, the race is mainly an out and back, with the course running the Great Falls Loop three (3) times before heading back on the Potomac Heritage Trail towards the Finish Line. It’s ever changing terrain throughout, with some faster and slower sections, including rocks and possibly mud. See both a detailed and summarized course description in the course guide, beginning on page 7.

Lessons Learned from Race Reports

  • Headlamp is mandatory, with race starting at 5am, you’ll have about an hour of running in the dark
  • Be sure you know which color ribbon is your race, as there are several races going on at the same time and over the weekend
  • No parking at start/finish for anyone – all participants and spectators must take a shuttle from designated area
  • A lot of the climbing happens between miles 10-40, with the exception of one 125 foot climb around miles 6 and 43.
  • Runners do a 7 mile loop 3 times in Great Falls State Park, which is miles 15-36, and which includes most of the rocky sections. Most runners report this loop is a bit confusing, so pay attention to signage and turns.
  • None of the climbs are big, but they are relentless ups and downs between miles 10-40
  • Seeing as it’s late April in DC, the weather could be anything from cold and rainy to hot and humid
  • Lots of race reports talking about muddy, wet, possibly snowy conditions
  • Stream crossing early on, in the dark.
  • Be ready for wet feet most of the day and possible shoe-sucking mud
  • None of the hills are particularly long, but some are quite steep, so save your energy and power hike them if that’s easier than running for you
  • The beginning and ending 10 miles can get really muddy if it rains, so it’s all the worse with runners trampling over it all day


Total gain/loss: 4,600/4,600

Ft/mile gain: 92

Total climbs: ~10 anywhere from 100-250 feet of climbing each

Elevation profile

Aid stations

Total aid stations: 14, not including Start/Finish

Furthest distance apart: 4.8 miles

Locations: Miles 4.3, 7.8, 10.5, 15.3, 19.4, 22.2, 26.3, 29.1, 33.2, 36, 40.8, 43.5, 47, 49.2, 50.9

What’s available: Chips, Pretzels, Saltines, Oranges & Bananas, Skittles, M&Ms, Peanut Butter & Jelly Sandwiches, Potatoes & Salt, Vegetable Broth, Energy Gels, Electrolyte Hydration, Pepsi & Mountain Dew, Water

Per the  permit with National Park Service, single-serve portions are required at the following aid stations (basically from miles 15.3 – 36):
– Great Falls Park Aid Station (miles 15.3, 22.2, 29.1, 36.0)
– Old Dominion Aid Station (miles 19.4, 26.3, 33.2)


Please note the following requirements at these Aid Stations:
– No cut fruit – Only whole pieces
– Individual packaged food items including Chips, Pretzels, Saltines,
Candy, etc.
– No Energy Gels
– No prepared food including PB & J (Event will provide an alternative)

Crew access

Access Locations: Great Falls Aid Station, which runners pass 4 times at miles 15.3, 22.2, 29.1, and 36.0

Crew instructions/directions: There is parking at the aid station but you need a parking permit, which you can purchase at the park entrance. Make sure crew review the rules in the course guide.


Yes, after mile 27 and pacers can start from the Great Falls Aid Station on either the third pass at mile 29.1 or the fourth pass at mile 36.

Race qualifiers

4 UTMB points

Race reports

Jonny G’s 2018 race report (50k)

Strava activities and GPX files

Race Website

2018 50 mile course guide