Tyrosine intake and cardiovascular responses in a motivated performance situation

Ingesting the catecholamine precursor tyrosine can prevent decrements in, or improve, cognitive and motor performance in demanding situations. Furthermore, the biopsychosocial model of challenge and threat specifies that adrenal medullary catecholamine release plays a central role in the occurrence of a challenge state, which has been linked to better performance under pressure than a threat state. The present study thus examined whether acute tyrosine intake impacts upon challenge and threat states or influences cognitive and motor performance independently. A double-blind randomised crossover design with 49 participants (33 males; µage = 22.5 years, SD = 5.0) was used. Participants ingested tyrosine or placebo (150mg/kg body mass) 60 minutes before performing the N-Back task and a bean-bag throwing task. Cognitive self-reports and cardiovascular data before each task provided indicators of challenge and threat states. There were no significant differences between tyrosine and placebo on the cognitive and cardiovascular challenge and threat variables. Generalised Estimating Equations analyses found that tyrosine was associated with better performance than placebo on the bean-bag throwing task, but not on the N-Back task. A significant interaction effect showed that challenge and threat states were more positively related to performance in the placebo condition than in the tyrosine condition. This suggests that tyrosine may have attenuated the detrimental effect of a threat state. The present study breaks new ground in relating the impact of a dietary supplement to challenge and threat states and finding that tyrosine may in some cases attenuate the negative effects of a threat state.