The link below holds a great article detailing the effects of coffee for the more athletic of you out there; it poses a balanced argument for the use of coffee detailing a common sense trial and error approach to finding the exact level of caffeine required for you to perform at your peak. What works for some may not for others.
I couldn’t say the exact caffeine I consume but the effects on me are clear from a physiological perspective. I consume 3 coffees at routine times during the day to function my best stopping at 2pm to allow the effects to calm down towards the evening. When playing Tennis I do notice a performance boost especially with my concentration levels, this often turns poor tennis mediocre.
Caffeine in products
Do you regulate your caffeine intake or have an understanding of the amount required to perform at your best psychologically or physically?