Both get bogged down in delays and litigation more than 90 percent of the time. Cumulative injuries, such as back problems and repetitive motion injury, develop over time.
Permanent injuries cause a permanent loss of earnings or earning capacity.
Both types raise difficult questions for employers and insurers. For example, when a worker injures his back, doctors say it may be the result of years of wear and tear. The law says insurers can try to claim partial responsibility, but usually an employer accepts the employee ''as is'' when hired and is responsible when an injury occurs on the job. Cumulative injuries are vulnerable to delays, participants in the workers comp system agree, because of the difficulty of assessing the severity of pain, the damage done and the payments due within an immensely complicated program. The fastest-growing types of disputed injuries on the North Coast from 1991 to 1996 were those to arms and wrists, probably reflecting the cumulative stress of working on computer keyboards and long hours doing repetitive office tasks.