Ok--good point. Aerobic fitness is great from running.

For me, as a triathlete, running is SUCH a risky thing. I put in big miles, and I CAN'T get hurt and achieve my goals. I run what I need to run to get the job done, but I don't overdo it. However, i run on tired legs all. the. time. I never train feeling fresh when I run. For my purposes, that defeats the point of long distance tri training. I want tired legs to feel normal. That's also probably why I feel like running just brings me down in the other things :-)

Running is really tough on your body. Cycling and swimming...not so much. I guess that for me in the overall picture, I am always balancing the risks of running with the overall aerobic fitness that I need.

I did some serious high intestsity cycling sessions a couple of year ago, and a little bit of running tempo work, and I had a HUGE HM PR. Ok, I am going to keep thinking :-)