The word begins with an “M,” has 10 letters, and four syllables. Possess it, and you can do great things. Lack it, and all the things you do are never more than mediocre.

Yes, it’s that powerful.

It’s also elusive and fleeting, so you need to be on a never-ending search for it. So what is this mystery word, this abstract noun that can improve your health and fitness more than an orthodontist can improve your smile?

Motivation.

What occurs when what you can’t get out of your head is not some lame love song from the eighties but an irrepressible urge my high school baseball coach called “gotta-wanna.” Unfortunately, the latest survey done by the Centers for Disease Control and Prevention (CDC), reveals that only 24 percent of adults “gotta-wanna” about getting the proper amount of exercise.

If that percentage strikes you as too low to be legitimate, here’s why. While many of the other 76 percent get what the CDC regards as sufficient aerobic exercise — 150 minutes a week of “moderate-intensity aerobic activity,” such as jogging, swimming, or fast walking — what they don’t do are the two weekly sessions of “muscle-strengthening activities” also suggested, the best of which is weightlifting.

Despite this, what comes next is not written to give you the “gotta-wanna” toward weightlifting. There’s little good in feeling that way if it goes away when you go from reading to lifting.

To keep that from occurring, you need to recognize an incorrect idea about weightlifting. That the be-all and the end-all is to add muscle mass.

To dispel this falsehood, think of the amount of weight you use to perform an exercise the way you view golf clubs. No single club is inherently superior to another.

You select one over another because each club best suits a specific situation and your strengths and weaknesses. For instance, where your big, brawny buddy may use his three iron for a tee shot on a par-3 hole, you may use your one wood because you lack his power.

Similarly, the weight you choose to use when lifting is merely a matter of what amount is needed to elicit the proper response. And that proper response (at least once a week after two or three weeks of allowing your body to acclimate) is to take the targeted muscles to the point of failure.

In other words, your muscles need to sing out a specific lame love song from the eighties: “I can’t go for that / Oh —- no can do.”

If you want the end result of your weightlifting to be more muscle, the singing needs to start after six to eight reps. But if your goal is good health or to combat muscle loss as you age, there should be“No can do” should come after 15, 18, or even 20 reps with a significantly lighter amount of weight.

Too many who are turned off to weightlifting do not realize that using higher reps to reach muscle failure still gets the job done — and is certainly safer.

Add weightlifting’s ability to help a bicyclist get better to the last two benefits, and you have the three reasons why I drag these old bones down to my basement and lift weights for at least 60 minutes two or three times a week. I cite my specific situation to explain how former hardcore lifters can still stay motivated as they age despite that fact that they use far less weight than they did years ago.

The difference for me is so much less that it might make me cry. If I were to bench press now, for instance, I don’t think I could do six to eight reps with what was my warm-up weight at age 28.

So I don’t even try.

Not only would that hurt my motivation, but it would also hurt the elbow that was shattered and pieced together with screws and wires in 2002. So how do I work my pectorals, the chest muscles, to work muscle failure?

I simply grip two Olympic plates the way you’d grip a half-pound hamburger, lay back on a bench, and perform a pressing motion.

While I used 25-pound plates initially to figure out the most effective technique (the thumbs need to be higher fingers and the plates should be closer to the belly button than the nipples at the point of full extension), I can now grab two 45s, shoot for 10 reps, and get some extra motivation to eek out the last two from the fear that the plates might come crashing down on my head.

Taking your lifts to that point once a week — though you don’t have to do so as dangerously! — is the best prescription for counteracting the inevitable loss of muscle mass that results from aging. And for those not battling sarcopenia, it elicits a response that not only makes adding muscle more likely (provided you eat properly) but also makes you feel a whole lot better.