The karate practitioner relies upon generating incredible tension in their own bodies in order to power their blows and blocks; in Goju ryu karate (and I'm sure others), there even exists a "high-level" practice called sanchin kata, in which the practitioner focuses on maintaining a high level of tension throughout their bodies.
Here's a youtube link of sanchin kata: http://www.youtube.com/watch?v=g5xD2Ph9CPo
The systema practitioner focuses on tension control as well, but in order to eliminate it: they use conditioning drills to learn to both relax and feel the tension in their partners, and use "slow motion sparring" to remain relaxed and develop sensitivity to the energy of attacks.
Here's some youtube links of solo systema conditioning:
And here's one of Vladimir Vasiliev being Gumby:
I personally feel that I understand the point of karate's sanchin kata more than I do the slow motion of systema: for a striking art, tension = better transfer of energy, and having studied more physics than I'd like to, that makes perfect sense to me. Some of the "relaxed" strikes of systema I find questionable: I can see how a relaxed strike could result in an inelastic collision (your hand doesn't bounce, say), and the end result is less energy being redirected back into your striking arm, but some from the youtube clips I've seen of systema striking, it looks a little bit too much of preconditioned uke's responding out of habit rather than an actual, powerful, relaxed blow.
Of course, being relaxed for the grappling and throwing aspects of systema make perfect sense, since it aids in your sensitivity to attack energy. This is what (I believe) we wish to attain in aikido as well.
However, as a noobie I don't really know of any specific exercises per se that teaches an aikidoka how to manage or control their own tension other than perhaps kokyu dosa. I know when I'm on the mat most of the yudansha working with me always remind me to relax when I do any technique, which I try to do as best I can, but do you think that aikido could benefit from more "tension management" exercises, such as karate's sanchin kata or systema's tension conditioning?
For Goju ryu, sanchin kata is the bedrock of their training. Apparently systema practitioners devote much of their training time to these tension conditioning exercises. Do you think tension management and basic conditioning exercises (other than just kokyu ho or tai no henko) should play a larger role in aikido training, or should we just continue focusing on the "learn technique, learn to break out of technique, learn to create your own technique" methodology?