Final answer:
MUAC clinical checks involve assessing the clasp-knife response, testing muscle strength against resistance, and conducting the pronator drift test to evaluate for upper motor neuron (UMN) diseases.
Step-by-step explanation:
When checking for mid-upper arm circumference (MUAC), the clinical sign that should be evaluated is the response to resistance during muscle contraction. This involves checking for the clasp-knife response, which is a sign of upper motor neuron (UMN) disease. This response is observed when there is initial resistance to passive movement of a muscle, followed by a sudden release to a lower state of resistance. Additionally, muscle strength is assessed by having the patient contract muscles against resistance, such as lifting the arm against the examiner's pressure. Lateral differences in strength can indicate a deficit in one of the corticospinal tracts. Another important test for UMN lesions is the pronator drift test, where the patient extends both arms with palms facing up and closes their eyes; a drift towards pronation could indicate motor system failure.