Effects of L‐Tyrosine Ingestion on Endurance Performance in Mentally Fatigued Cyclists

ABSTRACT This study investigated whether L‐tyrosine supplementation enhances endurance performance in mentally fatigued cyclists. Twelve recreational cyclists completed two constant‐workload tests to exhaustion cycling tests under two experimental conditions at 80% of maximal endurance power output: L‐tyrosine ingestion (300 mg/kg) under mental fatigue (TYR‐MF), and placebo under mental fatigue (PLA‐MF). Mental fatigue (MF) was induced by a 60‐min Stroop task (ST). Oxygen consumption (VO2), rating of perceived exertion (RPE), and heart rate (HR) were measured throughout the cycling test. Time to exhaustion in the TYR‐MF condition (459.9 ± 199.6 s) was higher when compared to the PLA‐MF experimental condition (398.7 ± 222.1 s) (p = 0.008). The increase (i.e., slope technique) of RPE throughout the cycling to exhaustion was lower in the TYR‐MF (0.560 ± 0.184 a.u.) than in PLA‐MF (0.673 ± 0.251 a.u.) (p = 0.03) experimental condition. No differences were observed between conditions for VO2 and HR data (p > 0.05). L‐tyrosine ingestion increased endurance performance by approximately 16% in mentally fatigued cyclists. This effect was accompanied by a reduction in RPE slope during cycling to exhaustion. Therefore, these preliminary findings suggest that L‐tyrosine supplementation may offer moderate benefits in performance for cyclists under mental fatigue conditions, although confirmatory studies with larger samples are needed.