Pure conjectural or anecdotal but it is my intuition that there is something to it
EDIT: My running theory is related to hormesis or tolerance where the body produces an opposite effect to the ligand to maintain homeostasis and there is not a sufficient dose of the exogenous drug taken to override the body’s compensatory reaction
So even tho caffeine is a stimulant (adenosine antagonist) it actually causes the body to produce the opposite reaction, causing the reverse effect of making you sleepy
This is purely personal experience, but I’ve found that the usually warm beverage that caffeine comes in + the increased heart rate helps to warm up my muscles, which makes the muscles relax more easily.
Checks out. Like a warm bath before bed