Deep heat patch delivers up to eight hours of deep relieving warmth directly on the site of muscular aches and pains joint stiffness backache strains sprains and menstrual cramps heat increases the blood circulation in the skin and deeper tissues when muscle spasm or tension is caused by local lack of oxygen for example after exercise the increase in local blood flow induced by heat can reduce the feeling of pain by bringing more oxygen to the area pain sensing nerves are stimulat