Originally posted by Ghost Fox
If I'm right, by dynamic tension you mean executing a waza very slowly while flexing the muscles intensely. The theory is that by doing the movements slowly you make sure your doing it with perfect form. The dynamic tension of the muscles speeds the development of muscular memory and allows you to perform the technique faster, stronger and more relaxed during normal practice.
If you're doing this all alone, how do you know what you're doing actually works with a partner? "Perfect form" is not perfect technique. Perfect technique is one that changes itself to fit your partner, not one that changes your partner to fit the technique. This might be good for unranked beginners, but I don't see how this would be good for anyone with any skill in the art. Form only gets you so far until more subtle things like timing and initiative become a lot more important.
If you're doing it just to get "tired," do some push ups and sit ups. Run to your dojo then train for two hours.