The heat patch contains natural components including
iron, coal, water, and salt. These components become warm
and give off heat when they interact with the air. Heat
increases the blood flow to the area of application via
vasodilatation, leading to smooth muscle relaxation and a
decrease in the perception of pain. The heat patch supplied
heat at a constant temperature of approximately 38.9C
(102.02F) over a surface area of 180 cm2. It may take up to
30 minutes to reach therapeutic temperature. This device
was capable of supplying warmth for the complete duration
of the 8-hour study period.32,33 The positioning of the
abdominal patch on the lower abdomen was standardized,
and the patch was held in place by adhering it to the
participant’s underwear, which completely covered the
patch while it was in position. The participants were given
information and a form about the heat patch, and the heat
patches were applied on the first day of menstruation for 8
hours, during 2 menstrual cycles in the HPG.