This is an old document I wrote years back but I think for the most part it is a good concept.  
Variable Isometric Plane on External Resistance
Long ago in a far off land there was a man who possessed strength that rivaled today’s elite athletes.   His training consisted of providing for his family, plowing fields, hefting trees out of the woods, slaughtering game, splitting wood and specifically being an all-around bad mother lover.  Often times a tale can be told of men from back in the day that were freaks and able to heft tremendous amounts of weight.  They may or may not lift weights they have probably been exposed to some form of labor in life that has caused some chronic hypertrophy. These men are probably neurologically efficient at using their posterior chain and usually have a grip that would make a lesser man piss himself or at least fall to a knee.  Some of these legends never competed in the games of iron.  The men that did compete the freak shows and strongmen likely did very little if any preventative works in their life.  These freaks probably never external rotated unless they were going to throw a horse shoe.    
Considering the aforementioned legends, a person is left to wonder how these demigods would be able to make gains, and press ungodly amounts of weight without doing specific retraction, depression and external rotation work.   A one track mind perspective a individual that prioritized a major lift like a press or a squat would likey not stray to far from that lift unless he or she had a substitute.  Way back before ipods, 4 axis controllers, and smith machines the old school lifter had a plethora of choices.  For legs the legend could squat, deadlift, clean or snatch.  For chest if he wanted to press he could do overhead press, overhead dumbbell press, dumbbell bench or barbell bench.  The legend would likely choose a barbell.  Now remember this is a bit speculative however the legendary lifters were very limited in what they could do, but were still able to do impressive amounts of weight. 
If the legend plateaus or is injured on a lift. His limited knowledge of the injury tells him he needs to figure something out.  The legend must rectify the situation as the bar and the lift taunt him.  He may be forced to do a different lift, lower the weight due to injury or push through the pain on a lift and insure more injury.  The two wise choices are change.   The legend decides to lower the weight but still feels said pain or impingement. He modifies the lift hands in hands out still pain presents itself.  Finally the legend does something that repetition has taught him not to do rather than just lift the weight he decides to modify his contraction against the bar.  He notices less pain he realizes whatever he did has diffused a bit of the pain.  He repeats the lift with more weight the same results though the pain does not fully sub-side it has lessened. 
How does this work how, how can an individual injured go from symptomatic to asymptomatic by varying contraction style.  This is where Variable Isometric Plane on External Resistance comes in.  Using VIPER in an individual can pinpoint areas of weakness specific antagonist weakness.  Antagonist weakness often plays a part in inhibition of an agonist muscle group.  On the press an individual can use VIPER theory to help rehab overemphasis on agonists.  An individual can feel the agonists working on a press more easily on the eccentric phase so long as a Tempo is followed.  I would suggest 5-0-2-0 Tempo or something along these lines.  Three separate isometrics in the weak range of the lift holding for 5-10 seconds at each spot will also work. 
Emphasis on the Press
            Eccentric Phase (negative)
-Pulling the bar apart (this helps initiate rhomboids and retractors)
-Bending the Bar horizontally (this helps to emphasizes shoulder blade in retraction)
-Elbows under the bar (so not to rely on an inefficient compensation pattern in relation to specificity of the lift)
-Control of the eccentric phase of the lift (you will emphasize a controlled negative especially in the weak range of motion)
            *at any time you can emphasize a range by stopping the bars eccentric phase and focusing on the isometric torque you are placing on the bar
Concentric Phase (positive)
            –Pulling apart and bending the bar(you should feel the bar most on the inside of the thumb and the pink due to the nature of the isometric resistance you apply on the bar)
            – once you reach the top if you have to reset scapula so that they are retracted do so and begin to emphasize posture of the next rep before doing the next eccentric
Closing thoughts
            I would suggest doing 3-5 sets @ 70-85% of your  rep maximum 6-8 reps of your 1 rep maximum.  (Use technical failure as your guide for your 1 rep maximum)
            Consider following VIPER work with a1-5 true work set if you are feeling spry. 
            Consider ending with dumbbell work on a press emphasizing stretch at the bottom of the press and finally finish with external rotation and retraction work.
            VIPER work does not replace prehab work rather it is specific to prehab. 
This concept it more of an idea that branched from four different sources:
  The idea stems from Jerry Telle style lifting
  Structural Balance  from Charles Poliquin
  Dave Tate on a pressing article
  Kinesiology and the Cardinal planes of movement