Also urging trade up purchases are clocks with advanced features, such as a nap timer function, which WestClox carries, and a demand for louder alarms, which appeals to everyone from sleep-craving teenagers to the overfatigued.
The fatigue theory, proposed in 1984 by Bennie, attributed the pains to "the little legs (that) have performed an unusual amount of work during the day" and became overfatigued. A second explanation, the anatomic theory, was published in 1983 by Hawksley.