Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Caffeine (Anhydrous) | L-Tyrosine | |
|---|---|---|
| Category | Training Compounds | Amino Acids |
| Standard Dose | 100-400mg daily (1-3mg/kg bodyweight for cognitive; 3-6mg/kg for athletic performance) | 500-2000mg daily |
| Timing | 30-60 min before exercise or cognitive demand. Avoid within 8-10 hours of bedtime (half-life: 5-6 hours, but CYP1A2 polymorphisms cause wide variation). Morning preferred. | Morning on empty stomach (competes with other large neutral amino acids for BBB transport). 30-60 min before stressful tasks or exercise. |
| Cycle Duration | ongoing with periodic tolerance resets (1-2 weeks off every 8-12 weeks) | As needed or cycle 4-8 weeks on, 2 weeks off |
| Evidence Level | strong_human | strong_human |
Caffeine is a methylxanthine that primarily acts as a competitive adenosine A1 and A2A receptor antagonist. By blocking adenosine's inhibitory effects on neural activity, caffeine increases alertness, reduces perceived exertion, and delays fatigue. Downstream effects include: increased dopamine, norepinephrine, and acetylcholine release; enhanced calcium release from sarcoplasmic reticulum (direct muscle contraction enhancement); increased fat oxidation via enhanced lipolysis (HSL activation through cAMP/PKA pathway from PDE inhibition); and central drive enhancement (reduced RPE). Caffeine also inhibits phosphodiesterase (PDE), raising intracellular cAMP.
100-400mg daily (1-3mg/kg bodyweight for cognitive; 3-6mg/kg for athletic performance)
30-60 min before exercise or cognitive demand. Avoid within 8-10 hours of bedtime (half-life: 5-6 hours, but CYP1A2 polymorphisms cause wide variation). Morning preferred.
ongoing with periodic tolerance resets (1-2 weeks off every 8-12 weeks)
L-Tyrosine is the precursor amino acid for catecholamine neurotransmitter synthesis: tyrosine hydroxylase converts tyrosine to L-DOPA (rate-limiting step), which is then converted to dopamine, norepinephrine, and epinephrine. It is also the precursor for thyroid hormones (iodination of tyrosine residues on thyroglobulin produces T3/T4) and melanin (via tyrosinase). Under conditions of acute stress, catecholamine turnover increases dramatically, depleting brain tyrosine pools. Supplementation provides substrate to maintain catecholamine synthesis during stress, sleep deprivation, cold exposure, and cognitive demand.
500-2000mg daily
Morning on empty stomach (competes with other large neutral amino acids for BBB transport). 30-60 min before stressful tasks or exercise.
As needed or cycle 4-8 weeks on, 2 weeks off
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