The purpose of applying paste or jelly when running an EKG (Electrocardiogram) is to reduce skin resistance. This conductive gel ensures better conductivity between the skin and the electrodes, resulting in a clearer and more accurate recording of the heart's electrical activity. Without the gel, poor contact can lead to high resistance and artifacts in the EKG trace.
Reference:
Thaler, M. S. (2018). The Only EKG Book You'll Ever Need (9th ed.). Wolters Kluwer