Okay, quite straight forward. My thoughts indeed caffeine might influence the sympathetic nervous system directly or indirectly.

I suspect you'll be best of finding participants who already don't drink caffeine (which will already be harder to find). I predict If you find caffeine consuming volunteers such as myself - many will lie at least once over a duration of 60 days about their caffeine intake. Which wouldmake your test irrelevant.

I would like to perform this test. However, I don't think I can mannage over the next 60 days, soon I start to travel for work again, and I'm not quite sure if I can implement such a test within my routine presently.

But I'll check out if it would work, it would take some dedication for me to stay off the caffeine as well for such a time honestly.

The soda's ... Obviously ;)