It’s not the first study to find unique benefits in this amino acid. In 2008, a separate study looked at how theanine affected the body when paired with caffeine—which is useful since most pre-workout amino-acid supplements also contain caffeine. The researchers found that, in comparison with when caffeine or theanine was consumed alone, the combination of the two ingredients resulted in improved mental speed and accuracy and a reduced susceptibility to distraction (like the hot girl on the pec flye machine). These are just two studies atop a laundry list of similar research outlining the benefits of amino acids. The truth is that you can consume amino acids at any point throughout the day and you’d be doing yourself a favor—both physically and mentally.
REFERENCE: Unno, K, et al., Exp Physiol., 2012 June 15. (E-pub ahead of print); Owen, G.N., Nutr Neurosci., 2008 Aug.; 11(4):193-8.