As many as 80% of Americans will suffer an episode of back pain at some time in their lives. Back problems are among the main reasons for doctor visits, and they can be excruciatingly slow to heal.

What people don’t realize is that most back injuries are predictable, and how to avoid them might surprise you. Here are the six worst mistakes that people make that hurt their backs…

Weight and Effort Mismatch

I see this all the time. Suppose you lift a box that is heavier than you expected. You get it a few inches off the floor and then realize that it’s really heavy. It’s going to crash back down if you don’t bring all of your strength into play. The sudden contraction of unprepared back muscles can cause an instant strain.

Or maybe you’re lifting a box that you think is heavy but turns out to be as light as a feather. All of the muscle force that you generated causes a “snap” in the muscles (and the box goes flying).

Self-protection: Before you lift something, test the weight. Slide it a few inches, or lift just a corner. You have to know what you’re dealing with. If it’s heavy, get your legs under you…use the muscles in your legs more than the muscles in your back. If it’s light, lift with a smooth motion—you won’t need that initial hard jerk to get it moving.

Overhead Bin Reach

If you think that the cramped, knees-to-chest seating in today’s airplanes is hard on your back, wait until you use the overhead bins. You will pay in pain what you saved on checked ­luggage.

Travelers often overstuff their ­carry-ons. A 20-pound bag that’s easy to carry (or wheel) can feel like 50 pounds when you’re off-balance and reaching overhead. Unloading also is a hazard. You probably had to angle, wedge and stuff your bag to get it to fit. You will have to give it a hard yank to get it out, a motion that is very hard on the back.

Self-protection: Pack light. If you’re in reasonable shape, you probably can manage, say, a 10-pound bag when your arms are extended and you’re standing on tiptoe. Use both hands to place the bag in the bin…don’t swing it up with one arm. Store it with the handle facing out. That way, you can grip the handle with one hand and use your other hand for support. For anything much heavier, put it in checked baggage—it’s worth it even if you have to pay.

Super-Soft Chair Recline

It feels good to sink into a soft chair or sofa—but it is hard to extricate yourself from the pillowy depths. Surprising fact: Sitting in a soft chair is hard work.

When you sit in a firm chair, your back is supported, so it relaxes. But a soft chair doesn’t provide the same sensory input, so the muscles stay contracted. After an hour or so, you might notice that your back is hurting even though you haven’t done anything more strenuous than read a book or work the TV remote.

Self-protection: When you’re settling in, choose a chair that provides a decent amount of back support. It doesn’t have to be hard, but it should be firm.

Also helpful: If you have a history of back problems, you probably will do better if you stand up for one to two minutes now and then—say, every 15 or 20 minutes.

The Car Trunk Lean

How many times have you felt a “pinch” when you lift a suitcase or a sack of groceries from a car’s trunk or cargo area? It’s not so much the weight that causes problems but your position. When you bend over and lift, you are at a mechanical disadvantage. You are not using the big muscles in your legs. Your back muscles aren’t very strong. Their job is to stabilize your spine, not help with heavy lifting.

Self-protection: Get as close to the vehicle as you can before pulling the item to the front of the trunk and taking it out. This allows you to bring your leg muscles into play. Most people stand back from the rear of the car because they don’t want to get their clothes dirty. Step in closer. It’s easier to clean your clothes than to deal with a month or two of back pain.

Twist and Shout

“Twist and shout” is what I call the stab of pain that occurs when people use a twisting motion to bend over. Suppose that you’re picking something up off the floor that’s a little bit off to your side. You might pivot at the hips and swing one hand down to snag it. Don’t! This is an unnatural motion because the spinal joints are designed to shift from front to back, not side to side. Twisting strains the soft tissues and can lead to sprains and spasms.

Self-protection: Before you pick something up, take a fraction of a second to move into a position of strength. With both feet facing the object, squat down and pick it up. Face it square, and use your legs more and your back less.

Shoveling Anything Heavy

Back specialists see a lot of new patients in the spring after they have been working in the yard shoveling mulch, dirt or gravel. The same is true after ­snowstorms. Even when snow looks light and fluffy, each shovelful packs a lot of weight—and you never move just one shovelful.

Self-protection: Warm up before picking up the shovel. Walk around the house for a few minutes. Stretch out the muscles in your back, legs and arms.

Once you’re outside, let your legs do the work. Bend your knees when you load the shovel, then straighten them when you lift. Don’t bend your back any more than you have to. And don’t take the heaviest shovelfuls that you can manage—if you’re grunting, it’s too much.

Also helpful: Home-supply stores stock a variety of ergonomic shovels that make it easier to stand upright when you’re shoveling.