Jan 19, 2008

Shiftwork schedule factors: speed and direction of rotation

Adapting to rotating shifts can be affected by the speed of rotation and the direction of rotation. Speed of rotation means the number of consecutive day, evening, or night shifts before a shift change occurs. Direction of rotation means the order of shift change:

  • A forward rotation is in the clockwise direction, from day to evening to night shift.
  • A backward rotation is in the counterclockwise direction, from day to night to evening shift.

Different rotation speeds also affect a worker's ability to get used to change of shift times. We have already talked about the same situation under permanent versus rotating shifts. Longer rotations (for example, three to four weeks of working the same hours) are sup-posed to allow workers more time to get used to night shifts.

However, workers usually return to a day schedule on their days off. A fast rotation (every two days, for example) allows no time to get used to night work. Some researchers prefer the fast rotation, because the worker quickly gets through the tough shifts and then has a couple of days off. Very fast rotations are used in Europe more than in America.

Direction of rotation can affect the ability of circadian (daily body) rhythms to adapt to the change in work times. Sleep, for example, is a circadian rhythm because each person sleeps for part of every day. Some researchers suggest that a forward, or clockwise, rotation is better for helping a worker adjust to new sleep times.

This suggestion was made because it is easier to go to bed later and wake up later than earlier. Our body rhythms make us feel more awake and alert in the early evening. This makes it harder to fall asleep earlier. Backward rotations work against the body rhythm by forcing the worker to go to sleep earlier and earlier.

Although we don't have hard and fast numbers, it seems that back-ward rotation schedules are used frequently in the United States. It is not completely clear why. It is partly because of custom (We always did it this way) and partly because workers like the “long change.”

In the long change, workers pick up an extra day off when going to evening shifts after night shifts. This happens because evening shift starts late in the day, which leaves most of that day free for non-work activities.

We'll continue this discussion of shiftwork schedule factors.

Other recent posts on shiftwork scheduling include:


Source: Plain Language About Shiftwork (NIOSH)

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