In a general sense, the term “co-contraction” is used to describe the simultaneous activation (tension) of antagonist muscles around a joint. This physiological mechanism may be successfully applied for body training. Factually, co-contraction method is some kind of voluntary focused muscular tension without using any external resistance. Sometimes people name that Visualized Resistance Training (VRT)

http://www.vrtsystem.com/ or Dynamic Visualized Resistance (DVR) http://transformetrics.com/forum/showthread.php?t=9465, however, co-contraction of antagonistic muscles is a basis of these methods of training.

Although co-contraction or VRT, DVR may be effective for gaining strength and muscle mass, they are not very popular in the fitness community. Why?

I think that a main problem why many people do not consider co-contraction (VRT, DVR) as an effective method to gain strength and muscles is a difficulty to create and maintain high levels of muscle tension that could be equal to heavy weight loading. Indeed, even after regular co-contraction training, we can reach in our muscle antagonists ~40-80% of 1RM. However, some tricks can help to increase our muscle tension almost to 1RM and provide high levels of tension through the full range of movement.

Trick #1: ISO addition before the full range of movement. We can perform the isometric co-contraction, which helps to reach maximal tension in antagonistic muscle pairs. Then keeping this ISO co-contraction level in the muscles, we can move through the full range of movement.

Trick #2: Tension pumping. I’ll try to explain it for the biceps curl. 1. Partially curl the biceps (up to 90 degree) with the strong triceps resistance. 2. Return your arm in the beginning (straightened) position with keeping co-contraction in the biceps and triceps. (You can add one or two partial curls to increase your co-contraction before the full movement) 3. Add your muscle tension and make full biceps curl 4. Keep the curl position and relax biceps and triceps for 1-2 sec (breath in) 5. Partially straighten (up to 90 degree) your arm with co-contraction of the triceps and biceps (negative/eccentric movement) 6. Return to the bent position with keeping muscle tension (Again, you can add 1 or 2 partial movements to increase co-contraction) 7. Add your tension in muscles and make full straightening.

This is one rep. Perform 6-10 reps with good co-contraction and you will get VERY STRONG blood pumping in your arms and shoulders. This principle, you can use for any muscles.

Note: Add muscle co-contraction and move when you breathe out.

It is worth noting that some bodybuilders and martial artists successfully use muscle co-contraction in their training. For example:

http://selfresistance.boards.net/thread/11/marlon-birch-exercise-routines

https://www.youtube.com/watch?v=N2VgxgM4wr8

https://www.youtube.com/watch?v=xWMZvuryHd8

https://www.youtube.com/watch?v=2y9r_xXnpcE

……