Effects of L-Tyrosine Ingestion on Endurance Performance in Mentally Fatigued Cyclists
Participants
n=12 recreational cyclists
Protocol
Two constant-workload tests to exhaustion at 80% of maximal endurance power output
Conditions: 300 mg/kg L-tyrosine under mental fatigue (TYR-MF) vs placebo under mental fatigue (PLA-MF)
Mental fatigue induced by a 60-min Stroop task; VO2, RPE and HR measured throughout
Key Results
| Metric | Effect |
|---|---|
| Time to exhaustion | 459.9 ± 199.6 s vs 398.7 ± 222.1 s (TYR-MF vs PLA-MF, p=0.008; ≈ +16%) |
| RPE slope | lower in TYR-MF (0.560 ± 0.184 vs 0.673 ± 0.251 a.u., p=0.03) |
| VO2, HR | no difference between conditions (p>0.05) |
Findings
L-tyrosine (300 mg/kg) offset part of the endurance decrement produced by mental fatigue, with a flatter rise in RPE. The authors call the findings preliminary and ask for larger confirmatory studies. Inference, not tested: the study has no non-fatigued condition, so it does not show whether tyrosine helps a rested athlete.
Limitations
Small sample (n=12); recreational athletes; time-to-exhaustion protocol (not TT); only one comparison — both conditions under mental fatigue; high dose (300 mg/kg → ~25 g for 82 kg, impractical for most)
Practical Application
In 12 recreational cyclists mentally fatigued by a 60-min Stroop task, 300 mg/kg L-tyrosine lengthened time to exhaustion at 80% of maximal power by about 16% (460 vs 399 s, p=0.008) and flattened the RPE slope; VO2 and HR were unchanged. Relevant where cognitive load precedes or accompanies the effort — long, hot or tactically demanding races — not to ordinary training.
Not from this paper; the base's own practice: if trialling tyrosine, do it before a lower-priority race or a race simulation, start below the study dose and check GI tolerance; a ~24 g dose for 80 kg is a lot of powder.
Cross-check REF-215 (Jongkees review): tyrosine helps cognition under acute stress and, per that review, its potential for enhancing physical exercise "seems minimal" — this trial is the exception the review anticipates (performance under a cognitive stressor).
How this entry was checked and changed
Content correction 2026-09-27
Practical lead was house dosing ("150-300 mg/kg", "12-25 g", a personal race week) -> replaced by the study's finding with its numbers; house advice labelled as the base's own practice.
"Works only when neurotransmitter synthesis is actively stimulated by stress" -> the trial had no non-fatigued arm; now labelled inference.
"GI tolerability was not checked" -> the abstract does not report it; wording softened. Cross-reference REF-012 (duplicate) -> REF-370.