The strained muscles that affect millions of American workers, from white-collar professionals who spend hours at their computers to poultry workers who process chickens, are proving to be painful as well to the Obama administration.
Labor regulators came into office vowing to press employers to reduce injuries from repetitive motion, an affliction that caused 28 percent of the workforce to miss days on the job in 2009.
But the administration has found itself in a pitched battle with industry, which fears that federal involvement in the matter will result in a massive financial and legal burden.
The U.S. Chamber of Commerce, which represents more than 3 million businesses, has lobbied vigorously against any additional regulation.
Last week, the administration appeared to take a step back. The Occupational Safety and Health Administration withdrew a proposed rule requiring employers to record repetitive-motion injuries. OSHA saw it as a modest new requirement, simply adding a separate column for such injuries on forms most employers already must maintain.
The move followed an order by President Obama on Jan. 18 that regulatory agencies review rules with an eye toward scuttling those that are unnecessary or put "unreasonable burdens on business."
OSHA also withdrew a proposed interpretation of noise standards that could have forced some employers, who already provide employees with ear protection, to retrofit equipment to make it quieter.
When it comes to repetitive-motion injuries, the politics are so charged that even a minor change sent ripples through the labor and business communities.
"We're angry and we're disappointed by this," said Peg Seminario, director of safety and health for the AFL-CIO. "If the administration is going to respond to something that should have been a small deal, we're quite concerned about what this might mean for things that have a broad impact."
And, despite the administration's attempt at detente, conflict continues to brew between federal regulators, who want to reduce injuries, and business leaders, who view new rules as ill-conceived.
"If we look at this problem honestly, there is little doubt that musculoskeletal injuries remain one of the biggest workplace health and safety problems in American industry," David Michaels, assistant secretary of labor for OSHA, told a meeting of the American Bar Association in March. "No agency calling itself the Occupational Safety and Health Administration can go long without addressing this issue."
The first step, Michaels has said, is to gather more accurate data on the scope and pattern of the injuries by requiring employers to note them separately on injury logs, so they are not lumped together with other workplace injuries.
Michaels said the agency "temporarily" pulled the proposed rule requiring such recordkeeping because it needed to consult further with small businesses to determine how the change would affect them.
Research has shown that some of the soft-tissue injuries caused by repetitive motion can be avoided by using equipment such as wrist guards or modified computer keyboards, and by taking regular breaks or stretching.
Still, the science surrounding musculoskeletal disorders is inexact, and it can be unclear whether a muscle injury happens on the job or off.
Businesses say they should not be saddled with costly new equipment or procedures when there is doubt that the injury is job-related.
"It's not a simple diagnosis - it's not like saying you've got a cut finger," said Marc Freedman, director of labor law policy for the Chamber of Commerce. "Most of the symptomology is subjective. [It] doesn't mean employees are lying, it just means that it's very hard for an employer to determine if this is an MSD that occurred in the workplace."
OSHA has stepped up enforcement of health and safety laws since Obama took office, hiring more inspectors, issuing more citations and increasing penalties for employers who violate federal standards.
But the fight over musculoskeletal injuries has been raging since 1979, when OSHA began to research the issue.
After 20 years, the agency created rules that were enacted in the final days of the Clinton administration.
In 2001, Congress invoked the rarely used Congressional Review Act to overturn the rules. Under the act, the executive branch is forbidden from proposing similar regulations in the future unless specifically approved by Congress.
Even before Republicans regained control of the House in November, Michaels had said it was unlikely that OSHA would try for new rules covering repetitive-motion injuries.
Instead, the agency wants to take a broader approach by enacting a regulation that would require employers to identify and take steps to avoid all significant workplace hazards, including musculoskeletal disorders.
Several states, including California and Minnesota, already have such requirements. And some employers have voluntarily taken similar approaches, he said.
"Many employers say this is easy - this is a no-brainer," Michaels said. "They know a well-managed company manages safety and health programs. I think we'll get tremendous support for this. Instead of having employers look at standards they have to meet, they'll look at all the risks in their own workplaces and develop a program to abate those risks."
Seminario, of the AFL-CIO, countered that a broad mandate to identify risks and mitigate them leaves too much discretion to the employer. "It's a helpful tool, but it's not a substitute for standards," she said.
Meanwhile, the Chamber of Commerce will object to any risk prevention program that includes musculoskeletal disorders, Freedman said. "That becomes de facto regulation and it's back to the same argument," he said.