Everyone is an expert on Getbig. Broscience is rampant here. Anecdotal experience is all one needs to be an expert. 
Yes, I didn't think blood flowed through tendon and ligaments as in the case with muscles. I remember going through a treatment for my knees called Prolotherapy where they injected a substance into the tendons to cause inflammation that stimulates your body's healing mechanism producing collagen and stimulating the growth of new tendon fibers.
I also am not clear on this notion of stabilizing muscles. All muscles in a sense act as stabilizers but is there a special class of stabilizing muscles?
No doubt you are using more muscles to control a dumbbell press than you would a barbell press and even less so using a machine where everything is "stabilized" for you. But is training in an unstable environment a good thing in regard to strengthening the target muscle?
It seems to me that one must develop a skill, in this case balancing and keeping stable, to perform with a dumbbell then on a Nautilus machine.
That's why a beginner doing dumbbell presses will start to increase resistance rapidly but not because he is getting stronger but because he is getting better at balancing those dumbbells.
If an unstable environment was conducive and more effective to increasing muscle size and strength then wouldn't it follow that the more unstable the environment the better? Of course, it is harder but is it better for muscle hypertrophy? Squatting on a Swiss ball is much harder than on a solid floor but because of it's unstable environment you simply can't tax your quads to the extent that you can on a solid floor due to the unstable environment. You are developing a skill, coordinating your muscles, balancing -- stabilizing as it were -- to squat on a Swiss ball which does not necessarily translate into putting the target muscle, presumably the quads, under maximum load.
Sure you use more of everything to balance those dumbells but whatever muscles you are using to develop that skill could it not be addressed more effectively by targeting those muscle specifically? And it would also seem that the more unstable the environment that more likely you are to hurt yourself as the margin of error is greater. The "bar" or plane of resistance will always be consistent with say a Hammer Press than with a Bench Press where you might deviate from the left or right or up or down as you begin to fatigue or simply get sloppy.
