Combining L-theanine with caffeine is often referred to as ‘smart energy’. While caffeine does a great job of boosting energy, it can have a jittery effect, which detracts from an optimal workout. L-Theanine promotes relaxation, without having a sedative effect. The result is clean energy that increases focus and concentration, leading to an optimal workout.
Effect
Magnitude of Effect
Level of Evidence
Consistency of Research
Conclusion
Studies
Relaxation
High ↑↑
10/10
Very High
A notable increase in relaxation (without sedation) appears to occur, as assessed by neural measurements (such as alpha-waves) or self-report surveys.
Stress
High ↓↓
10/10
Very High
Notable reduction in response to acute stress in the available research.
Blood Pressure
Low ↓
8/10
Very High
As far as we can tell, it can reduce blood pressure increases in response to caffeine or acute stress, but it's unclear if it has any chronic effects.