Any comments related to how much "synergy" there is between run training and cycling training would be appreciated.

This is pure guess, but there doesn't seem to be nearly as much synergy between the two as I would have expected.

As for which regimine would make you a faster cyclist, I'd lean towards the 10 hours of cycling. This assumes that if you don't have to devote any energy/recovery time/etc to running, you're going to be doing those 10 hours at a higher intensity than you would if you added cross training.

Of course, this is going to hurt your running.

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"People think it must be fun to be a super genius, but they don't realize how hard it is to put up with all the idiots in the world."

I remember reading (but don't remember where) that there was a study that seemed to indicate that people who had enjoyed long cycling careers had weak bones. The hypothesis was that heavy sweating had leached calcium out of their bones. The pounding that your body takes while running stimulates your bones to grow stronger. There it is-- synergy in the big picture.

As far as implications for one week or one season of training goes, I really don't know.

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I'm not sayin', I'm just sayin'

If you can lose weight and stimulate your mind by getting some running in then there is chance to raise your w/kg and stoke your cycling fire a bit. I'm considering running in the offseason as well.

I think it was "Bicycling" magazine that ran an article about bone weakening in hardcore cyclists. Not enough weight bearing exercise was one of the theories.

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Sure it's funny till somebody gets hurt...then it's hilarious.

Holy shit...you guys ride 10 hours per week on a trainer ? I did all of 10 hour of riding all winter indoors. The rest was running and XC skiiing. Come spring, I ramped the bike quickly and good enough to get top 10 bike splits in most of my tris. That being said, this is triathlon I am talking about...but I have several roadie friends who do negligible biking all winter and are studs in the summer on the bike. They do however tend to pile on some speedskating miles which have huge crossover.

I find running plus XC skiing as great crossover to biking.

If I were you, I'd go for the 5 hours trainer+ 3 hours leg weights + 4-5 hours running plan. That would be solid off season

Dev

I believe there is some cross-over benefit from cycling to running, and very little the other way around. Bottom line, there is no substitute for sport specific training, although I'd say a plan like Dev's suggestion. sounds pretty sensible for the winter.