Whether you’re short on time or the gym is packed, you can still get a fantastic total-body workout with one single piece of equipment: the Smith machine.

The Smith machine is basically a barbell on a track housed inside a squat rack. It has a predictable trajectory that goes straight up and down, which makes it great for training solo. The barbell has a hook on either side, and a simple twist of the wrist spins the bar, locking it onto any of several notches along the outside of the track. This means you can set the bar at any starting height, allowing you to transition easily from standing and lying to sitting and more. Smith machines also have safety stops that can be set to any height along the machine, preventing the barbell from descending farther, thereby protecting you from injury and acting as a virtual training partner.