SACRAMENTO, Calif. -- Rosaura Navarro picked strawberries in the fields near Watsonville until she wrenched her back and leg while lifting the baskets of fruit four years ago.

Back injuries are notoriously hard to diagnose, and Navarro says doctors could not pinpoint the source of her pain. Nevertheless, the 30-year-old woman she has been getting $110 a week in workers' comp instead of the $420 she made picking crops.

Such benefits may be in jeopardy as California tries to overhaul the most costly workers' compensation insurance system in America.

California's 91-year-old system has been troubled for the better part of the past decade, but now, with premiums doubling and tripling, the economy stagnant and businesses threatening to leave the state, fixing it has become a priority for lawmakers and Gov. Arnold Schwarzenegger.

Schwarzenegger wants to require doctors to use "objective medical findings" to determine if an employee has a work-related injury. Injuries would have to be "reproducible, measurable or observable." He also wants to require employees to show that a cumulative injury -- one that develops over time -- was substantially caused by work.

Unlike many states, California covers all industries and all workers, such as field hands like Navarro and employees of small businesses. California also makes it easier than many states to claim a work-related injury; among other things, it covers cumulative injuries and occupational diseases that other states do not.

Because of those factors and others, the total paid in workers' comp premiums in California has gone from $6.4 billion in 1997 to an estimated $25 billion in 2003, according to the California Chamber of Commerce. And the average cost of dealing with workplace injuries has more than doubled, climbing from $2.68 per $100 of payroll in 2000 to $6.30 per $100 in 2003 -- the highest rate in the nation.

Business groups portray the problem as less a matter of fraud and malingering on the part of workers and more a case of too much subjectivity in the way injuries are diagnosed and rated in severity.

Too often, said Chamber of Commerce lobbyist Charles Bacchi, two workers with essentially the same injury will receive wildly different benefits. One doctor might prescribe costly therapy, while another might give the worker a painkiller.

Bacchi said such "highly subjective" evaluations may lead to a worker getting "a permanent disability award for something that's not necessarily warranted."

The changes proposed by the governor could affect Navarro and the thousands of other workers with similar injuries that are not easily detected by an X-ray or other diagnostic tool.

Attorneys and doctors said the governor's proposal would be particularly harmful to California's 900,000 farmworkers, who frequently complain of back pain because of the stooping, bending and lifting required to pick crops.

"I can only empathize with the field worker who is injured and has back pain that may or may not show up with objective findings on an X-ray or an MRI or what have you," said Dr. Ramon Jimenez, former president of the California Orthopedic Association. "To discount them, to cut them out of the benefits because they have pain or subjective symptoms and you cannot measure, it is absolutely wrong."

The problem may well be worse in California, where the close-to-the-ground crops and tender fruits and vegetables such as strawberries, cilantro, almonds, pomegranates, dates, oranges and avocados have to harvested by hand rather than by machine -- a backbreaking job.

Instead of requiring the specific diagnoses of problems, Democrats want a law that would allow the state to re-regulate the workers' comp premiums that most businesses must pay -- an idea Schwarzenegger said he is open to considering. Rates were deregulated in the mid-1990s.

Schwarzenegger made repairing the system a campaign pledge. Months into the job, he is struggling to work out a compromise between business groups, backed by the Legislature's Republican minority, and workers and attorneys, who are supported by Democrats who control both houses.

Without a deal, Schwarzenegger has said, he will help a business coalition put its proposed fix on the November ballot. Already, supporters of that plan are circulating petitions to collect the more 598,000 signatures needed to put the measure to a vote. The deadline is April 16.

The reasons given for the workers' comp crisis are many. Union leaders and workers' attorneys say insurance companies have been jacking up rates to make up for the ruinous price wars that took place in the 1990s after the elimination of minimum premiums.

Mark Gerlach, a consultant for the California Applicants' Attorneys Association, a group of lawyers who represent injured workers, said workers' comp costs are higher in California in part because it is simply more expensive to live here and medical costs overall are climbing.

Either way, Norman Eagle, vice president of the family-owned Eagle Container in the Los Angeles suburb of Carson, said something must happen soon or his box company may have to lay off workers.

In the past five years, Eagle said, the company's workers' comp rates have nearly tripled, feeding a system that is "just a bloated monster."

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