I took another look at the study, mainly to answer some questions folks were asking me...
ahcuah, I like reading your posts but but I'm still not following your reasoning re shorter stride length/higher turnover equating to higher energy usage/reduced "efficiency". A longer stride requires more energy per stride than a shorter one. Take one big step or two small steps, if you cover the same distance, you've burned virtually the exact same amount of calories (
all other factors being equal).
I suspect that could also be demonstrated on a stationary, reclined bike. Lower the resistance but increase the turnover
or raise the resistance and lower the turnover... the biker should cover a mile with the same calorie count in both cases.
A huge factor affecting this in runners though, would be experience. A shod runner taking off his shoes and doing the higher turnover/shorter stride thing would at first feel awkward and tense and thus waste more fuel than an experienced BF'er who can just relax and ejnoy the ride.
Likewise, if the test subjects here were given a good month or two to really get used to running under the test conditions, to the point where it was second nature to them, then the results could have been different. (By that I mean, have a runner run exclusively in the weighted half-shoe sock thing on a treadmill for a month, and then test his "efficiency". Then have him do the same with the Nike Mayfly, come back and test, and he'll probably have the same results. Do that with 100 runners to get a good sampling, and there ya go).