A forewarning for the wise: Don't give up on your fitness-related New Year's resolution when that resolution seemingly gives up on you. To understand why, assume the following situation is yours.

For the last 10 years or so - after years of struggling mightily to achieve it -you've managed to remain at a weight that you once knew was a good one for you, your college graduation weight. But now, based on how your clothing fits and what you see in the mirror, you're confused.Something other than the number on the scale - you're not quite sure what - has changed. Your pants are tighter at the waist, your shirts are looser at the neck, and when you finally get the nerve to get naked in front of a full-length mirror, you look rounded, soft, doughy.What you see disturbs you enough to email me.The details you pass on allow me to diagnose what's happening to you. While you've been eating better than most and exercising enough, you've been neglecting one type of exercise totally: weight lifting.That, combined with the body's inclination to add body fat as it ages and loses muscle mass, makes it possible for you to weigh what you weighed at 21 when you're 41 and yet be sickened by your shape. To diminish your disgust, I advise lifting weights in order to mitigate the inevitable loss of muscle mass that occurs with middle age.So when the new year begins, you lift on Mondays, Wednesdays and Fridays, cut your weekly aerobic exercise time in half, and can't believe the difference in only 12 weeks' time.You actually weigh three pounds more than before, but it surely doesn't look like it. You look leaner. Your shoulders are a bit broader, you stand taller, and buttoning your pants is no longer a battle.So long, soft look. Hello, hardness.Better yet, you feel infused with an energy that allows you to do - and want to do - more. More at your job, your house, the health club.By May, that energy is gone. You work out just as hard as before, but it's a chore. The numbers in the weight room show you're doing less, but it certainly doesn't feel like it.So what do you do now? If you're typical, you diagnose yourself with exercise burn out and decide to stop working out for one week. Too often, however, that week turns into a month, and one month without any sort of exercise usually negates all the work in the three months before has done.For what you should do, reread the lead: Don't give up on your fitness-related New Year's resolution when that resolution seemingly gives up on you.True exercise burn out happens far less often than you'd believe. But what happens far more often than you realize is that a new routine revitalizes you.It's not that the original plan was poor. It's that your body has adjusted to it. It no longer breaks down the muscles the way it used to, so there's no need for them to build up and improve.Consider what Jeremy Hughes, co-owner of J&K Fit in Nashville, Tennessee says in an article for John Parrillo's Performance Press: "Everything [any type of workout] works for a while - but everything eventually stops working. . . . When one approach dries up" . . . "simply institute another."So in the aforementioned hypothetical situation, don't abandon weight lifting and your New Year's resolution; just train in a different manner.Whether it's lifting weights to improve your shape, training hard for a 5k race, or adding miles to your bicycling rides so you can participate in the local bike club's 100-miler, your body adapts to the increased stress after 6 to 8 weeks. At that point, you should reduce your effort for a week - not to stop exercising completely - and then build up to another increase in either time, duration, or intensity.To avoid the potential problem in May, I would have you change your weight lifting workouts at the beginning of March. Instead of continuing to lift weights that caused muscular failure between 10 and 12 repetitions, you'd be told to cut the weight in half but to double the number of repetitions.After a week or two of that, along with a similar reduction in your aerobic activity, you'd return to the 10-to-12 rep pattern with about 80 percent of the weight you handled before the change.These three weeks would feel easy based on what your body had grown accustomed to. After that, you'd use slightly more weight than you ever used before (by 5 or 10 pounds depending on the exercise), but for 5 to 8 repetitions.The heavier weight and the lower repetitions would stimulate a different type of growth in the muscles, one that your now-recovered body is prepared to handle. Employ a strategy like this, and you can feel as energized and optimistic five months into a new exercise program as you had at the beginning.There's no such thing as burn out when you know how to back off and build up.