Shortly before their shift, participants swallowed a VitalSense (Mini-Mitter Company, Inc,
Bend, OR) temperature sensor pill, and a data logger was attached to the participant waist
belt. The VitalSense monitoring system continuously measured T
at 1-minute intervals to
±0.2°F. At the end of shift, data loggers were removed, and T
c
c
data were downloaded. Core
body temperature data were included in analysis once T
readings stabilized (ie, readings no
longer affected by the intake of fluids and food). Continuous HR was measured at 1-minute
intervals throughout a work shift, using an ActiHeart HR monitor (Mini-Mitter Company,
Inc). The HR monitors were attached to participants before their shift and removed after
their shift.