If you're discussing what I think you are, complimentary training is the training a player will receive to none primary training skills. For example if you're training a center in inside defense his "Inside Def" skill will increase at a solid pace and he will receive complimentary training in shot blocking at a much slower rate.
Another example is my own team. Currently I'm training my forwards in jump shooting to boost the jump shot skill and I've a few pops in my players in inside shot as well.
The training skills analysis is pretty helpful to show the complimentary training of skills.
http://www.buzzerbeater.com/BBWeb/Forum/read.aspx?thread=... and the updated version
http://www.buzzerbeater.com/BBWeb/Forum/read.aspx?thread=...