I think knowing the science behind what you're doing can only make you a better martial artist...
if you drive a car, could it possibly make you a better driver if you know how an engine works? A car is a tool, just like your martial arts are a tool, and the more you know about them, the better.
For example, if my instructor does an block when I punch him, and my arm goes numb, if I didn't know better, I might think its just because he hits really hard, so I will probably not try to duplicate this when someone hits me, because he has a lot more strength than I do. However, having some knowledge of kinesiology, I know that he hit the radial nerve in my upper arm, and that it doesn't take a whole lot of strength to create the effect of numbing a limb. Therefore, I may work harder to target my strikes, rather than working on striking harder.
knowledge is NEVER a bad thing. The more you know, the better you can make informed decisions.
Personally, I think kinesiology is a must for any martial artist. When I injured myself, I was able to tell the doctor that the pain was specifically at the joint of the first carpal (the little bones in your wrist) and metacarpal (the long bones inside your hand that connect the wrist to the fingers). This told her exactly where the pain was, rather than saying "um...my hand hurts."
Kinesiology also teaches muscle movements, proper stretching, and how the muscles move. You'll learn about the difference between a sprain, a strain, and a hyperextension, and know what kind of injuries you can walk on, and what kind you need to immobilize. My martial arts are better because of what I've learned.
For example, did you know that the "hurdler's stretch" where you put one leg forward in front of you, and one leg bent at the knee to your side, with your foot next to your rear, is really, REALLY bad for your knees? nobody except hurdlers should do this stretch, EVER. The safe way to do this is to take the leg that is normally by your butt, and bend it inward instead of back, so your legs make a 4 shape. then bend forward and touch your toe as usual. I was shocked to see how many martial arts instructors used the harmful version of this stretch, and they all did it because they didn't know any better. An adjustment so simple could save some of their students a plethora of knee problems.
Just my $0.02
-Nightingale