Dexterity and agility tend to go together. Also, strength is related to dexterity/agility. A weak person will not have the necessary muscle control of a stronger person - but once you reach a certain point, strength decreases agility and dexterity; you become muscle-bound. This is not to say that a wimp or a bodybuilder is not necesarily dextrous - it''s merely to say that it''s less likely. This is primarily because each of these people did little to practice dexterity. A regimen of stretching in combination with weight training, for example, can indeed increase strength without becoming muscle-bound. Similarly, intelligence and strength are really independent.

I like the basic premise of what I''ll call your "exercise" idea - that running makes you tired, but also increases your endurance. I think this idea makes a lot of sense. When someone hacks and slashes a lot, their arm strength will go up. If he fences or picks pockets, his dexterity stats will increase, even though he''ll also get tired and start to fumble. So I really like that idea. But I think that stats should be independan; they shouldn''t in and of themselves harm other skills. The very fact tht you''re spending all your time studying spells instead of hacking monsters means that you''ll get wise but not strong; you don''t need wisdom to cause weakness. In fact, some skills should compliment other skills - if you become more agile, you should probably also become more dextrous.

An addition that could be useful is atrophy. If you haven''t done a spell in a while, it''ll take you a little bit to get used to doing it again. But keep in mind that this doesn not mean you forget spells altogether; it merely means you get a little "rusty." Likewise, muscles atrophy.

So what it boild down to is this: Skills don''t hurt one another; the fact that you devote time to one rather than another should be "punishment" enough. The build-up in skill is opposed by atrophy; in other words, you need practice not just to make perfect, but to keep it that way.

I hope all this makes sense.