Tractor pulling a trampoline - GIF

[JTG]

Despite initial appearances, these people actually know what they're doing (they have some level of gymnastic training), and they are using professional equipment -- that's a competition trampoline, which you won't often find outside of a gym because they cost anywhere from $6-12k.

The technique is called double bouncing, and in this case it's the only reason the person can keep bouncing while landing on his stomach, which doesn't let you add any more energy into the bounce. Without the double bouncing, he would get five or six bounces of decreasing height. It can also be used to get insanely high off the deck of the trampoline if done correctly.

They're doing a partial version, where two people use one leg to put their weight onto the deck as the third person comes down, such that you effectively have the weight of three people loading the springs. As the rebound begins, the two people at the sides shift their weight onto the frame and bend their other leg, such that they don't take any of the energy they put into the springs -- it is instead transferred to the third person, who goes proportionally higher.

This can be done with two (or more) people at full bounce, with one bending their knees and crouching on rebound to stay on the deck, while the other goes soaring. Back when I was training, I once hit the drop ceiling over the trampoline at my gym, which was 25 feet over the deck.

Note: double bouncing shouldn't be done on consumer-grade trampolines (the round ones), because it is very hard to control the direction of the doubled bounce, and you can find yourself far away from the intended landing zone. Enthusiastic double bouncing can also cause the deck to bottom out on the ground, and I know someone who sprained an ankle because of this.