Purpose of Review <p>Muscle groups differ in their sensitivity to the pharmacodynamic effects of neuromuscular blocking agents. Therefore, the results from monitoring depth of neuromuscular blockade in one muscle group cannot be assumed to represent the depth of neuromuscular blockade in other muscle groups.</p> Recent Findings <p>In particular the diaphragm and laryngeal muscles are far more resistant to the pharmacodynamic effects of neuromuscular blocking agents than the adductor pollicis muscle. As a consequence of this, diaphragmatic movement, which can be associated with poor surgical conditions, may occur despite having a train-of-four count = zero as assessed at the adductor pollicis. Additionally, the muscles involved in swallowing, such as laryngeal and pharyngeal muscles, are significantly more sensitive to neuromuscular blocking agents than the adductor pollicis. Thus, clinically significant impairment of swallowing can occur even though recovery of muscle strength, as assessed at the adductor pollicis, appears to be complete. Finally, the genioglossus muscle is far more sensitive to neuromuscular blocking agents than the adductor pollicis muscle and incomplete recovery of strength in this muscle can lead to inspiratory obstruction of the upper airway; and patients with obstructive sleep apnea are especially at risk for airway obstruction.</p> Summary <p>To correctly assess the impact of depth of neuromuscular blockade on surgical conditions, the anesthetist should be aware of the pharmacodynamic differences of NMBAs in different muscle groups.</p>