i know that i am going to open up a large bag of worms with this post but i have some concerns with the running economy articles that JK is writing. The first one is straight from an ex phys text book which anyone who has half a brain could pick up, read, understand (some more than others) and then regurgitate. the second article on the other hand, JK takes some liberties that i am not sure he should be taking.
regarding stride frequency. I have done a little literature check and it seems that in most scientific literature there is no basis for claiming that increasing stride frequency increases economy. in fact, there was one study that actually found a DROP in running economy with an increase in stride frequency. now, i know that daniels spent an entire olympics counting stride rates of elite runners, but i propose this. economy (at least in mechanical terms) is a relationship between stride frequency and stride length. stride length should roughly be determined or at least be partially due to force of push-off. this force generation is a result of different factors as well. probably the largest is muscle fiber type. if every athlete has a different fiber type make-up then trying to say, increasing stride rate for a runner who has a higher percentage of fast twitch fibers would actually result in a DROP in economy. I would argue that Daniels was looking at a population who had largly the same type of fiber make-up and thus were very similar in terms of performance, stride rate, etc.
so, just making a blanket statement that increasing stride frequency will increase running economy is not necessarily the best recomendation to make if one is talking purly in terms of physiology. let the bashing begin.