The main lower back muscles you need to know about are the erector spinae. Feel along either side of your spine just above your hips and you have a handle on your lower erector spinae.

Most lower back exercises—particularly those appropriate for beginners—don’t involve free weights or machines. It’s just you and the floor. Here’s what you can accomplish without any equipment at all:

Sitting puts your spine under a lot of pressure, much more pressure than if you stood all day, and particularly compresses your lower spine. That’s why your lower back feels sore after a day in front of your computer. When your back muscles are weak, you tend to slouch or arch your back, which places the spine under even more stress.

In addition to strengthening and stretching your lower back on a regular basis, you should get up a few minutes every hour when you’re sitting throughout the day.

Injury Prevention: Ironically, even people with chronic lower back pain tend to neglect lower back exercises, often because they’re afraid of inflicting even more damage. Also, while people have gotten the message that abdominal exercises help alleviate back pain, many don’t realize that lower back exercises are equally important in this pursuit. When one of these sets of muscles is stronger or more flexible than the other, your posture is thrown off kilter, and you’re more prone to back pain. This scenario is quite common.

The “feel good” factor: Strengthening your lower back helps you stand up straight, which, in turn, makes you look taller, as much as 5 pounds slimmer, and gives you a more confident, commanding presence.