One evening a couple weeks ago, my arm felt tight. And when I say tight, I mean painfully immobile.

After spending a sleepless night trying not to move my arm, I got dressed in a half-hour and set off for Health Services. After they tried their best for about two hours, I went home with a recommendation for Advil and rest. A second opinion cemented my demise: My rotator cuff had been strained.

Now, I’m not the world’s most exercised student — I’ve seen the inside of the Rec maybe 15 times in the last four years. I’m your average 21-year-old weight, which I won’t print, about 5- foot-8 with shoes. Despite my pain, Health Services pronounced me healthy as a horse.

How I came to be immobile that night, I can’t be sure. From my vast knowledge of rotator cuff wounds, I know strain can come from just about anywhere. But I bet it had something to do with my backpack.

Don’t get me wrong, I love my backpack. I bought the navy blue contraption in Athens, when I couldn’t fit everything in my suitcase, and it has served me well since then. Padded back, three extra pockets and wide straps have made for a pleasurable backpack experience.

It’s what’s in it that hurts. Namely, all the textbooks I have/haven’t read, as well as the necessary notecards, pencils, wallet, stapler, planner, notebooks, kleenex, ketchup packets, cough drops, etc.

According to the American Chiropractic Association, people of the 140- to 160-pound weight range should carry about 21 to 24 pounds on their back. I think I’m carrying about 20 more pounds of backpack than I should. Now, with the ACA measurements, that means I should weigh about 240 pounds.

When I went to a health fair here about a year ago, a local chiropractor nearly had a heart attack when she saw my load of crap on two straps.

“Well, I bet that’s part of your problem,” she said with a grimace. Nice.

She tested my posture with a magnetic thingy that somehow shot an instant image of my bones into a computer. I peered into the screen, noticing two stick figures, one that looked bent over.

“That’s you,” she said, pointing to the crooked lines. “And that’s a correct alignment,” gesturing to the straight-as-an-arrow figure, which seemed to be smirking at my forlorn stature.

“Do you carry your bookbag on one shoulder?” she asked. As if it’s a sin. I nodded, ears flaming.

After I walked my crooked butt out of the fair with my navy blue attachment (on both shoulders), I felt like I should do something about my Z-like posture. Upon the suggestion of others, I decided to buy individual notebooks and stop taking all my books to class. I also cleaned out the pockets of the pack, making it about 10 times lighter.

I ended up feeling better, mostly because I could throw the bookbag around a little easier. Not to mention my neck wasn’t bent at a 90-degree angle all day.

Now, however, I just injure parts of my body. I know my knees felt tight the other day. I bet that was because of the new inch-and-a-half book I get to read. It’s all connected & really.

One suggestion from the ACA was to do strengthening exercises for back muscles. Why is it if you’re already carrying 40 pounds, that isn’t helping build muscle? You’d think logically, by carrying that much weight, you technically are doing exercises, right? But you’d be wrong, because you’re really straining your rotator cuff or some equally important joint.

The moral of the story is, carry the amount of weight proportional to your body. Otherwise, you’ll have to lose some weight in the backpack or gain it yourself & about 140 pounds worth.