Tyrosine is an important amino acid used to synthesize neurotransmitters such as epinephrine, norepinephrine, and dopamine. Higher levels of these important hormones give athletes the “will to win.” During exercise, tyrosine depletion may decrease the production of these important chemicals, so tyrosine supplements may boost performance and prevent fatigue.
British researchers found that supplementing tyrosine (150 mgs per kilogram of bodyweight) increased endurance capacity in the heat, compared to a placebo. Test subjects took the supplement one hour before a maximum endurance test conducted in the heat (86° F, 60 percent humidity). Tyrosine increased endurance even though skin temperature, heart rate, perceived exertion, and heat sensation were the same as in the control trial. The study showed that tyrosine supplements prevented fatigue during a maximum endurance test in the heat. (European Journal of Applied Physiology, published online)