Adjectives

(s)labored, laboured, strainedlacking natural ease“a labored style of debating”
(s)strainedshowing signs of mental and emotional tension“her voice was strained as she asked the question”
(s)constrained, forced, strainedlacking spontaneity; not natural“a constrained smile”, “forced heartiness”, “a strained smile”
(s)agonistic, strainedstruggling for effect“agonistic poses”