quote:
...free weights are better then machines. This is because they require you to stabilize your body while lifting so your low back, abs, etc. also get work.Well...not necessarily. Compare a one-armed seated row on a cable machine to a one armed bent-over row with a dumbbell. With the freeweight exercise, you're posting the arm that isn't lifting the weight effectively stabilizing the upper body. With the cable machine exercise, the muscles in your torso bear the brunt of keeping your upper body in position.
Another tip for your rhomboids is to imagine cracking an egg with your shoulder blades every time you do an exercise. This completes the contraction.