New regulations went into effect Tuesday capping the number of hours medical residents can work in a week, a change celebrated by many at Harvard’s teaching hospitals but criticized by some as short-sighted.

Trainee doctors are now only allowed to work 80 hours per week, according to the new rule imposed by the Accreditation Council on Graduate Medical Education (ACGME).

Though the cap is not federal legislation—such legislative attempts to limit hours of medical residents have previously failed in Congress—ACGME has the power to take away the accreditation of those hospitals that allow their residents to exceed this limit.

The regulation also stipulates a 24-hour maximum length for resident shifts, a required one day off in seven and a mandated ten-hour period between certain shifts.

Backers of the new regulation support it as a means of enhancing the learning environments of the newest doctors and improving patient care.

Opponents have traditionally argued that dealing with long-hours and stress is a necessary skill for doctors, and that a limitation would compromise continuing patient care.

On Tuesday this debate began to play itself out on the hospital ward floors, as schedules had to be refigured and some residents may have gained a few hours of sleep.

According to Wilder Professor of Pediatrics R. Alan B. Ezekowitz, head of pediatrics at Massachusetts General Hospital (MGH), the change was planned well in advance in his department and thus went smoothly.

“This is something we knew would happen about six to nine months ago,” Ezekowitz said. “We’ve been planning for it like a military operation. The changeover has been extremely orderly, we started the transition a week ago.”

Some departments already had hour limitations in place, meaning the new rules were hardly noticed.

The regulations are hitting other departments harder, Ezekowitz and others said.

Several predicted that the surgery program—which requires that residents receive training in a multitude of procedures—would have to make more serious changes in adjusting to the cap.

“One of the downsides is that in order to get enough experience, [the change] may lead to extending the length of time residents have to train,” Ezekowitz said.

And according to Rotch Professor of Pediatrics and Children’s Hospital’s Physician-in-Chief Gary Fleisher, the new rule will cost his hospital about $1 million each year.

“Schedules have been rearranged, attending physicians have assumed duties formerly performed by the residents or ancillary providers have been added,” Fleisher said.