Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Caffeine (Anhydrous) | Leucine | |
|---|---|---|
| Category | Training Compounds | Training Compounds |
| Standard Dose | 100-400mg daily (1-3mg/kg bodyweight for cognitive; 3-6mg/kg for athletic performance) | — |
| 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. | — |
| Cycle Duration | ongoing with periodic tolerance resets (1-2 weeks off every 8-12 weeks) | — |
| Evidence Level | strong_human | Strong |
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)
Branched-chain amino acid that directly stimulates mTORC1 signaling and helps trigger muscle protein synthesis when protein meals are under-dosed.
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