If there’s a three-word phrase I never dreamed I’d utter in my lifetime, it’s “my personal trainer.”

Rule No. 1: Never say “never.”

That’s right. I have engaged the services of a bona fide professional to help me keep my New Year’s resolution to get in shape, once and for all.

My personal trainer (MPT, for short) and new best friend (NBF) is the progeny of my son’s favorite teacher from fifth grade.

Seventeen years ago, she enthusiastically told me how her bodybuilder son had embarked on a career in the fitness industry and loved to work with people one-on-one, to which I replied, “If I’m ever in the market for a personal trainer, he’ll be the first person I call.”

At the time, I thought this was as safe and unlikely a promise as, “If I’m ever in Kazakhstan, I’ll give you a ring. We’ll do lunch.” Or, “When I win the lottery, I’ll buy you that Maserati you’ve always wanted.” In other words, “It’ll never happen.”

Again, see Rule No 1.

I learned an important lesson during my first half-hour session with MPT. To wit, the trainer-client relationship is fundamentally based on dishonesty. The client is expected to lie about her diet and exercise habits. (“I’m on a strict low-carb program.” And, “I put in five hours per week on the treadmill.”) In turn, it’s perfectly acceptable for the trainer to fib to his client. (“I’ll start you out with a mild workout.” Or, “Give me 15 more seconds on the steps,” which somehow becomes 30, then 60.)

A much bigger lesson came two days after my first workout when I discovered a mysterious phenomenon called Delayed Onset Muscle Soreness (or DOMS, for short).

DOMS is a deceiving and humbling thing. The first day, you bound out of bed, thinking,

“Hey! Those weights I lifted didn’t affect me at all! I could have gone another 10 minutes on that elliptical machine. I’m an animal! Mrs. Universe pageant, here I come!”

Come the second day, it’s a different, excruciating story.

First of all, don’t even think about bounding — out of bed or anywhere, for that matter. Be grateful you can lift your arm to reach the snooze button on the alarm clock. And don’t even try brushing your teeth with that ten-pound toothbrush. Eat a mint; save yourself the agony.

It will take you four solid hours to get dressed for work. Plan accordingly. The simple act of hanging up your robe will feel like red-hot daggers piercing your biceps. The grab bar in the shower will become your latest NBF, IF you can open the shower door with your feeble grip.

When you finally arrive at the office, take every precaution before you sit down at your desk to ensure you don’t have to budge for at least three hours. It won’t be possible without assistance from a co-worker, maybe two. And try not to scream as you trudge up the stairs. It will scare your colleagues and strain your abdominals.

MPT assures me that DOMS isn’t serious. Tiny tears in the muscles caused by strenuous exercise will heal and, in fact, strengthen the tissues as time goes on. But the soreness, he cautions, will always be with me.

“Even when you’re in great shape five years from now,” MPT says. “You’re still going to get sore, if you’re working out properly.”

This is supposed to motivate me? And, excuse me, when I’m in shape FIVE YEARS FROM NOW”!!? I was sort of thinking I’d be done by swimsuit season.

Make no mistake, my resolve is strong. I am determined to be the picture of health and body buffness by the end of 2009. Or 2014, as the case may be.

In the meantime, the crippling headaches during exertion are beginning to subside and I’m learning to love — OK, tolerate — the medicine ball. I can almost go backwards on the elliptical machine without suffering acute vertigo.

And, in addition to learning fun, new exercises like butt-ups, steps and karaokes (which have nothing to do with singing in bars, unfortunately — I could do that without breaking a sweat), I’ve found other NBFs, in addition to MPT: AIC (anti-inflammatory cream), HWB (hot water bottle) and MPI (my personal ibuprofen).