What should be held firmly to ensure the leg does not move during the administration of an epinephrine auto-injector?

When administering an epinephrine auto-injector, it is crucial to stabilize the leg to ensure that the injection is delivered accurately and safely. The correct area to hold firmly is the thigh. This is because the thigh has a large muscle mass that is the recommended site for intramuscular injections, which is where the auto-injector delivers the medication. By holding the thigh steady, you minimize the chance of movement that could lead to improper injection technique, such as the needle not fully penetrating the muscle or potentially causing injury.

Holding the thigh ensures that the device can be activated correctly and that the medication is delivered into the correct area. This position also helps to keep the recipient calm and secure during what may be a stressful situation, further facilitating an effective response to an allergic reaction. The other choices, such as the foot, knee, or calf, do not provide the necessary stability and muscle mass needed for an effective and safe injection.