"Come on, three more," Denise McLean urges me on, and when I've eked out three more repetitions of whatever physical challenge she's put me to now, she presses me again. "I lied," she says sweetly, with a smile. "Give me three more."

Looking at myself in the floor-to-ceiling mirrors that hide absolutely nothing, I can't help but smile. The signs of age etched into my face cannot be erased, but deep inside I know that high school would have been much easier if I'd felt this confident about my body back then.

I'd put on 10 pounds during my honeymoon, eating my way across Italy. After giving up smoking, I'd gained another 10. At the wedding, my husband had made me vow never to become "the fat lady on the beach" and that is how I found my way to Results, Inc., Denise McLean's personal training center.

While it seemed so unjust that a long-distance runner and triathlete such as I was should have to suffer the indignity of a "fat" class, the truth was my body fat was hovering at just under 30 percent, the generally accepted point at which one is considered obese.

The Nutricize program at Results basically consists of two parts. First, you go to class one night a week and learn about food (more on this in a future column). Second, you go into Denise's big, beautiful, private gym once a week and work out with a personal trainer.

Now the 20 pounds are long gone and the rules for sensible eating I learned in Denise's classes define my family's diet. My body fat stabilized at under 20 percent. What I didn't know when I signed up for the program was that I was about to get fast! Speed is a relative term, of course, I'll never win any races. I'll probably never win my own age group. Still, A 6:30 miles seems like speed to a middle-aged woman. After a year on Denise's program, I started collecting trophies. Where I once measured my age-group performance counting from the last to finish, suddenly I was counting from the front.

I am always surprised by runners who tell me they cannot see the point to weight training. The way to run faster, they swear, is to practice running. More, farther, and faster.

Perhaps the picture of Steve Spence on page 78 of the March, 1992 Runner's World will convince a few folks to get into the gym. A friend of mine dreams of the 2:40 marathon he know he has in him. He lifts weights three times a week, but until recently he wouldn't do lunges of squats or any of the really serious stuff. Recently he began to throw in a few sets of these, with light weights. Already he is feeling the difference in his training runs.

"In the late stages of the marathon, when attacking hills or the finish line, the runner with a stronger arm drive will do better and that arm drive comes from weight training," Bob Glover and Pete Schuder wrote in "The New Competitive Runner's Handbook."

Women in particular benefit from weight training because our muscles generally are less well-developed than men's. "Dramatic improvement in running performance are possible for women who develop some upper-body strength, usually through a weight program," according to Glover and Schuder.

To stay healthy, injury free, and prevent burnout runners must consider all the different elements that contribute to peak performance. Along with speed and endurance and other factors, strength plays its part.

In "Training Distance Runners," by David Martin and Peter Coe, the authors argue that runners who have been able to incorporate into their training a comprehensive program to improve the balance between their various major muscle groups "tend to have a sizable competitive advantage over those who have not done so." This is because "when all out competitive effort is required, those athletes with excellent total body conditioning will have a greater total strength, power, and work-output capability than those without such development."

Instead of doing many repetitions with light weight, a technique that develops muscle endurance, Spence opts for fewer reps with as much weight as he can lift, a strategy designed to build strength and bulk. "I want to be able to run a certain pace while recruiting as few of my muscle fibers as possible," he told Runners World. "I can only do that if I have stronger muscles that don't have to work as hard."

Clearly, bulk is a relative term. No runner is going to develop bulk like a professional bodybuilder unless he becomes one. One hour in the gym two to three times a week will not produce that "Terminator" look.

There are many books and magazines available that describe simple ways to put together a weight-training program. These are excellent. I recommend athletes sign on for at least two to three sessions with a personal trainer, if one can afford the $40- to $50-per hour price.

Trainers will push you to work harder than you will alone but will not let you injure yourself. One way they can do this is by gently helping you continue to move a given amount of weight once you are no longer capable of moving it alone. On your own, you must lift 100 percent of the weight. With help you can continue to lift 80 or 90 percent of it.

Another reason trainers are particularly useful for beginning lifters is that they will supervise your form as you are learning. A trainer will not allow you to develop the many bad habits beginners learn, primarily from copying the bad form of others in the gym.

The Principles of a Weight-Training Program

There are three fundamental principles to putting together a weight-training program, according to Martin and Coe. These are progressive resistance, increasing intensity, and specificity. The athlete must work with increasingly heavy weights to continue to grow in strength. He must increase the intensity of work by adding more repetitions. The exercise must focus specifically on the muscles one wishes to strengthen.

In putting together a weight-training program, follow these principles. Strength can be increased with a program of increasingly heavy work if one uses weights equal to at least 80 percent of the heaviest you can lift and performs three sets of six to eight repetitions. As the work becomes easier, increase the number of repetitions. When you can do three set of 12 reps, increase the weight an drop the number of repetitions back to six or eight.

If you do only 10 to 15 repetitions and do only tow to three sets of each exercise, you will build strength without adding bulk, according to Glover and Schuler.

Increase the difficulty (i.e., the weight) overtime to gradually strengthen your muscles. Exercise your muscles through their entire range of motion.

The secrets of success are to train regularly. Concentrate on developing those muscles you use most in your running. Work on balance. If running has developed your hamstrings, focus on developing equal strength in your quadriceps.

Work out with weights two to three times per week, if you can, with at least one full rest day between sessions to allow your muscles to recover. Generally, it is best to lift on days when you're not planning to run. Sometimes this is impossible. I prefer to run first and lift lighter weights afterwards. Many folks think its better to lift first and run easy. You choose. Just be careful not to get hurt. This means to take it easy if you feel tired.

I was unable to schedule more than one session per week of serious weight training. Clearly, it was enough. When combined with a solid running program, and some light swimming and bicycling, the improvement in my performance was dramatic. After one year of training one day per week with weights, I hit new personal records at every distance from 5K to the marathon and clipped 40 minutes off my prior year's showing in one particular international distance triathalon.

Begin your weight workouts by training larger muscle groups first, before moving to smaller ones. Alternate sessions between the upper body and lower body. It's a good idea if you have to run the same day to use that day to work the upper body.

Stretch gently before and after weight training. It's not a bad idea to stretch some in between. Don't over stretch.

Types of Equipment

There is a wide variety of equipment you can use for weight- lifting. The purists believe there is no reason to use anything other than free weights-those giant barbells and dumbbells that look so intimidating in the gym.

Generally you can increase your strength by doing resistance exercises, such as push-ups, where your own body weight provides the resistance against which you work.

You can use free weights, which are inexpensive and adaptable to a wide variety of exercises.

Or you can use variable resistance machines such as Nautilus or Universal, which cost a great deal but are efficient and, for some, easier to use and safer than trying to lift heavy free weights alone.

Sometimes the most surprising benefits of a weight-training program will be noticed when you least expect it. You'll be in a hurry one day, unloading groceries from the car, and you'll notice that you grabbed four heavy bags and easily negotiated your way into the house. Or maybe you'll be bringing your bicycle up the steps and a neighbor will stop to chat. You're standing there holding your bicycle, which was once difficult to lift, and you notice you've had it hoisted in the air for quite some time.

Stop showing off!