Proper Tree Pruning.

Here are some articles concerning proper pruning (trimming) of trees.
 Ed Gilman: http://hort.ifas.ufl.edu/woody/documents/ch_13_mw06.pdf.  It mentions lion tailing on pages 9-12.
 http://www.treesaregood.com/treeowner/treeownerinformation.aspx.  These factsheets are published for homeowners by ISA. 
We are being taught that to help trees keep up their nutrient reserves we leave the "shade Leaves" in the center thicker than we previously have or are used to leaving. Notice the shade leaves are larger than the outer canopy leaves (in most trees). This design keeps the nutrient production (food production) continuing after the outer canopy stops photosynthesis (food production) because the leaf surface temperature exceeds acceptable levels and the guard cells close, or partially close, stopping or reducing food production and transpiration. This also helps during drought. The cooler shade leaves on the inside of the tree (inner canopy) keeps 'The money flowing into the bank' which is the tree's root system. Storage of nutrients is one of the four functions of the root system. These shade leaves grow off of what are often referred to as suckers. Suckers grow out of the root system. 'Epicormic Shoots' are what grow out of the interior branching and are a reaction to some kind of stress. Stress such as heat on the branch from sun exposure or over pruning or storm damage. There are more stresses a tree can experience. 
 I believe it was during the 2013 Texas Tree Conference that this was PROVEN to us (proper pruning and why) by one of the speakers who took us outside by the bridge near the convention center and brought out his light spectrometer.  It might have been Dr. Ed Gilman, or Dr. Smiley. I forget exactly who the professor was.
I hope this helps Google catch up on these facts.