My buddy’s girlfriend told me he was struggling with a bad back.

I could sympathize because I once spent 2 1/2 days flat on my own back in a hospital bed after shoveling one too many shovels full of gravel.

It felt like someone slashed me with a red-hot saber, and one of the witnesses said I dropped to the ground faster than anybody he’d ever seen shot in a cowboy movie.

The lady said the therapists supplied my friend with a traction machine.

I showed her the well-worn sole on one of my sneakers and told her, “I’ve been thinking about getting a new pair of traction machines, myself.”

Without batting an eye, she launched into a description of this traction contraption.

She said it has several straps and looks like it was designed for some other purpose than what it was meant for ... and possibly could be used as such by energetic and imaginative folks who are young and supple enough to do so.

There’s also a handle-operated pump, and she demonstrated the motion that’s required to work it.We were on the street where other people could see us, and I told her she should be careful when doing something like that, because passersby might think she was telling me how she had stabbed someone.

She said that after my buddy strapped himself into this thing and began pumping the handle, he described in colorful terms just how painful the experience was. Then when he unstrapped himself and tried to get up, he hollered and said his knee was hurting.

That’s how it works, I told her. When your back hurts and you try to compensate for it, you invariably injure something else.

My buddy and I both have trouble with our sacroiliacs (there’s one on each side, and they hook the spine to the pelvis). Bend at the wrong angle, and one of them goes out.

Another friend of mine was laid up for three days with a disjointed sacroiliac because he put a glass in the dishwasher the wrong way. I’ve done it while cleaning the toilet, and I’ve heard of guys disabling themselves by tying their shoes.

It makes for a wretched situation, because there’s no way you can get comfortable. Everything you do hurts, and you can’t sit, stand, walk around or even lie down without it nagging at you.

After hobbling around all day, I go to bed and somehow manage to get comfortable, at which point I fall asleep. Then at various times during the night, I have to get up for the same reason most middle-aged men have to get up, and the process begins again.

What’s odd is that I sometimes wake up in the morning, and the side I hurt feels OK — but the misery has migrated to the other side ... the one I didn’t hurt.

I also have discovered that I am more likely to drop things on the floor when my back is sore than at any other time.

My buddy’s girl said that after his first effort to use the traction machine failed, she told him to get back in it and try it again.

“He had to get down on his hands and knees and crawl back to it,” she said. “I told him to try hooking it up so it just pulls on his back and not his legs. He did that and said, ‘Hey, that feels pretty good!’ ”

That attempt having succeeded, she went home, and time passed.

She said the next time she went over to his place, she discovered that he hadn’t touched the device since her previous visit.

“Of course, he hadn’t put the machine back into the same position you start in,” she said. “He just left it the way it was when he got out of it, and when he tried to get back in, he said, ‘Ow! That hurts! ”

I told her that didn’t surprise me. Rita Rudner, the comedienne, describes bachelors as being “bears with furniture,” and that’s the absolute truth. We don’t put things back the way we found them. We leave them the way they were when we finished with them.

It’s also customary for us to attempt using things like traction machines before reading the instructions. I asked the lady if my friend read the instructions before strapping himself into the traction machine, and she said:

“Of course not.”

With her help, my friend apparently has now figured out how to use the traction machine the way it was designed to be used, rather than as an engine of torture that Torquemada would have envied.

I told her I regularly adhere to a series of exercises and stretches that are designed to strengthen my abdomen and back muscles, and they seem to help considerably. I’m able to bend over and touch my toes with no trouble, and my doctor once told me he has patients my age who have a hell of a time even touching their knees.

I also told her that a couple of days before we talked, I went outside and mowed the lawn — it’s not the easiest lawn to mow — and used the weed-whacker.

It took an hour or so and was good exercise. I worked up a good sweat and actually felt better physically afterward.

The next day, I spent a half hour sitting on the edge of a chair, bent over, feeding junk mail into my paper-shredder so I could take it to be recycled, and when I stood up ... .

But I’m feeling much better now.

I can get up and walk around without limping or listing heavily to one side ... which makes my right hip hurt, no matter what direction I’m leaning. I also can wash my face without having to squat down low enough to scrub with one hand while supporting myself on the sink with the other ... which makes my knees hurt.

As my dad used to say, “Golden years, my ... .”