The challenge begins! In the first minute, nobody passes out. Victory! Rulon and Justin take off at a good clip, and are the first team to get to a kilometer. Gray and Aqua trail them. Justin goes fast and sweats and gets all red and generally looks like he might have a heart attack. Ditto Rulon. 20 minutes into the challenge, the Yellow Team hits 3K, still followed by Gray, Aqua, and Brown. Soon enough, the Yellow Team is first to hit 4K, and Kaylee from the Gray Team busts into a sprint. It is all to no avail, though. Rulon harnesses his competitive energy and Justin harnesses his piss and vinegar and they finish first. The Gray Team finishes second, the Aqua Team is third, the Green Team is fourth, the Brown Team is fifth, and the Purple Team is sixth. All of these teams will definitely get their own choice of trainers. The Pink Team finishes seventh, Red Team is eighth, Orange is ninth, the Blue Team is tenth, and the Black Team of Dan and Don finish last. However, everyone completed the 5K in under an hour, and no one ended up in the hospital, so that's something.

The teams line up in the order in which they finished in the challenge and get to make their trainer decisions. The Yellow Team says that there's no way they can pass up immunity -- they're going with the unknown trainers. The Gray Team does the same thing! Olivia and Hannah are incensed and shocked. It would be kind of awesome if this was a vintage Let's Make a Deal trick and a big door opens to reveal that the new trainers are a pair of giant rocking horses. Sami is pretty surprised by how things are going, and acknowledges what a hard choice it must be to decide between the beloved all-star trainers and immunity. The Aqua Team is next, and Courtney says that she came here to be challenged, and knows that Bob and Jillian will do that for her. They're sticking with the evil they know. The Green Team have also been tremendously inspired by Bob and Jillian, and join the Aqua Team. The Brown Team goes for the unknown and immunity. The Purple Team clearly is going for Bob and Jillian.