It basically confirms what many here have been touting all along: cross training won't help your performance.
However it does point towards resistance training (weights) as beneficial for endurance athletes.

http://www.nytimes.com/2011/08/16/healt ... ss&emc=rss

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Exp001

it should be noted that strenght raining does not always mean weight lifting or bulking up. i do not know about cyclicst but a runner needs that bounciness in the step that sometimes is achieved by doing plyometric trainning. that explosiveness comes in handy during sprint finishes. the runner that has not tested his fast twich muscles woudl never be able surge during the last few meters. look at most olimpic distance and mid-distance races they are won by the guy on cruise control that can out kick everybody else. a former coach of mine used to say that one of the reasons americans alway suck on long distance races is because they lack the explosiveness of the other runners. he also mentioned that when you run long distances that the faster the pace you start, the faster the pace that you can hold. he used to say that if you get out at a pace of a 4:50 mile you will be able to hold a faster pace that if you got out at a 5:00 mile because once slow twich muscle engages you are on cruise control and therefore speed fluctuations are reduced.