Well Being: A negative has these exercisers quite positive

Roger Schwab is an impressive advertisement for his profession. At age 67, the owner and president of Main Line Health & Fitness in Bryn Mawr has an enviable physique. In recent months, however, he's been able to defy the usual rules of time and aging by improving his body even more.

He has added six pounds of muscle, and when he flexes his biceps, the belly of the muscle is as big and full as it was when he was an iron-pumping stud in his 20s.

"That's not supposed to happen," Schwab marvels.

He credits his gains to a new line of Swedish exercise equipment featuring an innovative tilting weight stack called X-Force. Schwab installed 14 of the machines in January, and his is the only gym in the United States to have them besides a mammoth fitness center in Gainesville, Fla.

Generally speaking, Schwab is an upbeat, positive guy, but when it comes to resistance exercise, he's become a proselytizer for accentuating the negative.

In 1976, Schwab was the first to bring Nautilus equipment to the Main Line. He's always been an advocate of safe, sensible exercise and equipment that makes workouts quick and efficient. These new X-Force machines, he proclaims, are "the greatest advance in strength training since the invention of the Nautilus machine."

There are three components to strength training: concentric, static, and eccentric. When you curl a barbell, you contract your arm muscles as you lift. This is the concentric or positive phase of the exercise. If you were to hold the barbell steady, this would constitute a static or isometric phase. When you lower the barbell, you are engaging in the eccentric or negative phase.

For many years, weightlifters and bodybuilders tended to concentrate on the positive or concentric phase and gave short shrift to the negative or eccentric phase, often dropping the weights mindlessly or supplying no resistance at all.

But exercise scientists, including Nautilus inventor Arthur Jones, have long known that the eccentric phase is more effective in developing muscle size and strength as well as bone density. Generally speaking, people are 40 percent stronger when they're lowering the weight, and eccentric exercise can make deeper inroads more quickly then concentric contractions.

An inroad is the depletion of momentary strength, repetition by repetition, from a set of an exercise. Typically, your strength drops about two percent per repetition. With the X-Force machines, the inroad rate is closer to three percent, which means you reach muscle failure more quickly, usually after six or seven reps instead of 10 or 12.

Schwab gave me a sheaf of studies that affirm the superiority of eccentric exercise, showing that it increases muscle strength and girth faster. According to a Swedish researcher, it also enhances tendons, ligaments, joint surfaces and the skeleton.

Stressing muscles while they're stretched or elongated causes more microscopic fiber tears, which ignites the muscle-building process. Muscle force during shortening is less than force during lengthening because it's harder to create a new bond than break an existing bond.

Ellington Darden, an exercise scientist in Florida who has written more than 70 books about bodybuilding, nutrition, and sports medicine, calls the X-Force machines "the most productive equipment I've ever worked with." In a study he conducted involving 50 subjects, he reported "outstanding" results in muscle gain and fat loss. On average, over 12 weeks, the men in the study lost 42 pounds of fat and gained 13 pounds of muscle; the women lost 27 pounds of fat and gained 7 pounds of muscle.

"The increased inroad has a stimulating effect on muscle that pulls fat cells from adipose tissue," Darden says, "so you build muscle and lose fat at the same time."

Another advantage of the eccentric or lowering phase of an exercise is that it's easier to maintain perfect form and more difficult to cheat, Darden says, thus reducing injuries to shoulders, hips, knees, and the lower back.

The magic component of the X-Force machines is the tilting weight stack, controlled by a motor, which reduces resistance during the positive phase and increases it during the negative.

Let's say you select 140 pounds on the X-Force Pec Seated Press machine. As you grasp the handles, the weight stack tilts to 45 degrees. Thus, as you perform the positive phase, you are moving 100 pounds of resistance (29 percent less than 140 pounds). As your arms reach maximum extension, you hold for a half-second, the weight stack tilts back to vertical, and you do a controlled five-second negative with 140 pounds. Ideally, you would continue performing 100-pound positives and 140-pound negatives for seven or eight reps.

Schwab let me try several machines, and my first reaction when the stack tilted and the heavier weight kicked in during the negative phase was "Whoa!" That's what he usually hears, Schwab says. Either a "Whoa!" or a "Wow!" I could tell immediately that I'd be sore the next day.

With these machines, all it takes for a thorough workout is less than a half hour once a week, Schwab said. "You don't need more, and your body almost can't stand it. A little goes a long way. It's not how sore you feel but whether you've gotten stronger. Muscle strengthening is a means to an end, and the end is a better quality of life."

The machines are mechanically complex and temperamental and if not used properly can cause problems, so Schwab insists that X-Force workouts be supervised by a personal trainer.

While I was getting my introduction, Tracy Hoffman, 44, a personal trainer at the club, was putting herself through her own workout. (Rarely do people use all 14 machines in a single session; too exhausting.) She began using the X-Force machines shortly after they were installed and she's become a major fan.

"It's a very intense workout," she said. "I've lost about 10 pounds, and the shape of my body has changed. I'm much leaner. I had leveled out on conventional machines, and X-Force enabled me to break through the plateau. It's changed the way I feel about my body and the quality of my strength."