By VERNE KOPYTOFF New York Times Service

LOS ANGELES -- The fit and not so fit were straining on weight machines and panting on treadmills recently at the local gym.

Monitoring the scene was a trainer who counted every pound lifted and offered advice like ``go slower.'' The trainer, tucked away in another room, was a computer.

And what it lacked in physical strength it made up for in its ability to monitor nearly every piece of fitness gear, recall the workouts of hundreds of members and calculate the calories burned.

In many gyms, members manage their own fitness routines or pay for a personal trainer. But now some gyms are finding computers a more attractive alternative.

These electronic trainers let the staff monitor clients' attendance, perhaps reducing the dropout rate by giving the gym information that can be used to sell membership renewals or encourage customers to return.

``We can print out a member's record and say, `This is the level where you started, this is where you are now, and this is how many calories you burned last month,''' said Rosanne Malogolowkin, the fitness and health director at the Ketchum Downtown YMCA. ``It helps their motivation a lot.''

But the cost of such technology may be too great for some fitness centers. In addition, some patrons are reluctant to use these systems, and others cannot use them because the kind of exercising they do is not compatible with wires and sensors.

To use the electronic trainer at this Los Angeles YMCA, members must complete a medical evaluation by staff members and try out the fitness equipment with one of the gym's counselors.

After getting set up, members log on to the system and call up their routines. Each person enters a personal identity code at a kiosk that looks like an automated teller machine and then again at touch screens on each piece of fitness equipment.

Eve Bonham, a legal secretary, was ready to work her pectorals on an inclined bench press machine. She started lifting, keeping her eyes on the screen as it counted down to her goal of 8 to 12 repetitions.

A graphic told her how far to push the weights and pull the handles back. In the end, she received a few beeps of praise and a ``good job'' on the screen.

``You know, I like that sound,'' Bonham said as she pressed ``done'' and read the instructions for which machine to visit next.

What guides exercisers through their routines here is the Fitlinxx interactive fitness network, made by the Fitlinxx company of Stamford, Conn. Its system has been on the market since 1995 and is used by about 200 gyms in the United States.

The other major manufacturer is Technogym, based in Italy. Its equipment, called the Technogym system, has been sold since 1996 and is used by nearly 66 fitness clubs in the United States. The system has a wireless design linking the exercise machines to the central computer and gym kiosk.

Nearly 35 percent of all new gym members quit in the first year, according to the International Health, Racquet and Sportsclub Association. Fitlinxx says the dropout rate in Fitlinxx gyms averages 20 percent.

One market where electronic trainer manufacturers expect growth is in hospitals, to help people with heart problems, diabetes and sports injuries.

No matter what the venue, electronic trainers are not cheap. Setting up an average gym costs at least $70,000.