So says the latest study. You can google it.
The conclusion is based on just 18-people. The testers probably had the human lab rats exerting themselves at times of day and doing exercises that they never did previously. Some probably never even drank coffee, either before or after exercising.
Of course, that does not slow anyone up when it comes to drawing significant conclusions from their data. Wasn't is Shorter that drank flat coke while running?