“Kneel down on your hands and knees and arch your back.”
You're exercising along with an exercise video at home. The teacher on the video is giving instructions for a stretching exercise and she says this.
Kneel down on your hands and knees and arch your back.
To "kneel down" means to get into a low body position. It can mean one of the following:
- your knees are touching the floor
- your knees aren't touching the floor, but your legs are completely bent and you're almost sitting on the ground
People usually "kneel" in order to pray, or to show respect to someone like a king or emperor.
"Hands and knees" is a common phrase to describe a body position in which your hands and knees are touching the ground or floor.
An "arch" is a circular shape. It can describe an architectural feature, like some doorways or gates that have a circular area at the top.
"Arch" also describes some parts of the body that take that shape. The middle part of a person's foot is known as "the arch" of the foot. "Arch" can be used as a verb to describe raising your eyebrows when something is interesting or surprising. And you can also "arch" your back, which means to bend it backward.
Confusingly, it's also possible to describe bending your back in the other direction as "arching your back". But most of the time it means to bend it so that your shoulders move closer to your hips, and your stomach stretches.