D.C. ambulance worker Frank Fishburne says he's lost count of how many times he's been injured on the job.

An emergency medical technician for 15 years, Fishburne's first injury came in 1975, when he suffered a herniated disk as he and another ambulance crew member brought a patient down a flight of stairs. Fishburne was in traction for a month.

Since then, Fishburne, 39, has experienced a raft of injuries while on routine calls. He has injured the nerves in his right hand, forcing him to wear a leather-and-metal brace. Once, he said, a stretcher he was carrying snapped, hurting his back and neck and causing permanent damage to his facial nerves. And last year, his worst back injury yet laid him up for six months.

As the number of ambulance calls has surged in recent years, so have reports of serious on-the-job injuries suffered by paramedics and emergency medical technicians. The injuries, in turn, have pushed the workers' frustrations up yet another notch and increased the staffing problems of a service that, even when fully staffed, is stretched to its limit.

Moreover, ambulance employees and officials are concerned that an increasing number of paramedics and technicians are quitting after only a few years of service because they are too physically debilitated to continue.

"We have recurrent trauma on ourselves," said paramedic Calvin Haupt, president of the ambulance workers union, Local 3721 of the American Federation of Government Employees. "We pick people up and put them down, tug and pull. It really limits our professional life. It's not really rational to think that anyone can expect to give this 20 years."

Officials of the D.C. Fire Department and the ambulance union estimate that on a typical day at least 10 percent of the city's ambulance workers are absent because of injury. A report released last year by the city's Office of Productivity Management Services said ambulance employees average 300 hours, about 25 days, of unscheduled leave a year, a substantial part of it sick leave. It called the number high by most standards.

The rate of on-the-job injuries among ambulance workers in suburban Maryland and Virginia is much lower than the District's. On any day in Prince George's County, for example, 3 percent of its ambulance employees are absent because of injury, according to Lt. Ron Siarnicki, public information officer for the Prince George's County Fire Department. In Fairfax and Montgomery counties, the figure is 1 percent and 3 percent, respectively, officials said.

District paramedics and technicians say there are two reasons for the climb in injuries: the sharp increase in calls and a schedule that they say doesn't provide enough time between shifts.

Many criticize the ambulance service's switch last year to a schedule that requires them to work two straight days of 12-hour shifts, followed by two days off, then another three days of work. Previously, they worked four days straight, followed by four off.

The new schedule, ambulance workers contend, doesn't provide enough time for their aches and pains to heal and frequently forces them to work while injured.

"I've gotten my back hurt or pulled a muscle in my leg, and I haven't stopped working," said Fishburne. "You don't want to pull a unit out of service. You don't want to see the system go down."

The workload has become a significant problem, ambulance workers say. Ten years ago, the service received 75,000 calls, compared with 121,022 last year, a phenomenon that has accompanied the city's struggle with drugs and violence.

Paramedics and technicians say that statistic helps explain why more ambulance workers are leaving after only a few years of service. Those who do stay often find themselves battling nagging ailments, such as strained backs, aching knees and sore shoulders, which sometimes hamper their off-duty activities.

"When I'm at home picking strawberries, I'm on my hands and knees," said a paramedic who has worked in the District 12 years and who asked not to be identified. "I can't bend my back very long."

One result of the increased absenteeism is that firefighters trained as emergency medical technicians are being called upon more frequently to staff ambulances. In May, firefighters staffed 10.2 percent of ambulance shifts, compared with 1.8 percent in last September, according to figures from the firefighters union.

Ambulance workers and firefighters are rankled about firefighters pulling double duty.

"I think it has a devastating effect on the department," said Tom Tippett, president of Local 36 of the Firefighters Association. The increase in injury-related absenteeism has "created a huge overtime cost to the city, and they've started to restrict annual leave. It's had a dramatic impact on firefighters."

William McLaughlin, a veteran paramedic, shares Tippett's concerns, but for different reasons.

"The quality of care isn't as good when you have to pull {firefighter-technicians} to staff the units," McLaughlin said. "They're EMT-trained, but they're not experienced in handling the day-to-day problems of operating the ambulance. They can't recognize and handle certain situations."

More staffing is the obvious solution to the problem, but the city's budget crunch probably won't permit significant staff additions soon, fire department officials say.

Meanwhile, some people, including a few ambulance workers, believe too many emergency medical workers are taking sick leave even when they're not hurt.

"Unfortunately, injuries are very easy to claim," Tippett said. "If you hurt your back, who can look at you and say you didn't hurt it?"

But for the most part, paramedics and technicians say the system isn't being abused. "There are always a few who milk the system," said one veteran paramedic, "but by and large most people work in this field because they want to be out on the streets, not at home taking Motrin."