Crossing training in gaming means practicing different skills to improve certain skills in another game. Take the two FPS I play, Team Fortress 2 and Call of Duty 4. After spending the last two weeks unlocking scout achievements, I went back to COD4 as a sniper and I noticed a marked improvement on my close range accuracy and reaction time.
You may be wondering, “Why Scout? Isn’t there already a Sniper in TF2?”. That is correct, but playing the Sniper only works on skills you are already using as a sniper in COD4. The Scout’s scattergun and Force-a-Nature not only requires close range to be effective, but also aiming at the right spot on an enemy. Plus, because the Scout is a relatively fragile class, it relies heavily on its speed and agility to avoid getting hit.
Translate that back to COD4, where hitting almost any part of the body is lethal, and your sniper rifle becomes effective at all ranges. With increased reaction time, you can avoid the enemy’s bullets and switch to your secondary and finish them.
On the flipside, it may even help you as a TF2 sniper.
Every game focuses on a variety of skill sets, playing a diverse number of them will hopefully help improve your skills in all of them.