There have been an explosion of running economy papers in the last few years. I have reviewed many of them (and there are a few more to come when time allows). The results are somewhat mixed and the data is not as clear as the rhetoric and propaganda would have had you believe. To add to the mix, we now have this new study:
Softer and more resilient running shoe cushioning properties enhance running economy
Jay Worobets, John William Wannop, Elias Tomaras & Darren Stefanyshyn
Footwear Science Published online: 17 Jun 2014
Purpose: Several studies have investigated whether shoe cushioning properties have an effect on running economy. However, the findings have not been unanimous. Studies have shown both increases and decreases in running economy with soft shoes, while other studies have shown participant specific differences. Therefore, the purpose of this study was to add to the body of knowledge describing the effects of shoe cushioning properties on running economy.
Methods: This study was comprised of two experiments; one using a stationary metabolic analysis system to measure oxygen consumption during treadmill running, and one using a portable metabolic analysis system to measure oxygen consumption during over-ground running. Twelve aerobically fit athletes participated in each experiment. Two professionally constructed pairs of prototype running shoes were provided by adidas AG for this experiment (Soft shoe and Control shoe). The shoes were identical in construction with the only differences being the midsole material and corresponding stiffness and energy return.
Results: For both the treadmill and over-ground experiments, the Soft shoe condition was associated with statistically significantly decreased oxygen consumption compared to the Control shoe condition (Treadmill p = 0.044, Over-ground p = 0.028). In the treadmill experiment, 10 of the 12 subjects consumed less oxygen while wearing the more compliant/resilient condition, with an average decrease for all subjects of 1.0%. In the over-ground experiment 9 of the 12 subjects consumed less oxygen while running in the more compliant/resilient condition, with an average decrease for all subjects of 1.2%.
Conclusion: Running shoes with softer and more resilient midsoles were found to influence running economy by 1.0% on average during treadmill and over-ground experiments.
Nothing in the methods and analysis jumps out at me as being an issue. I am sure those that don’t like the results will have an issues with the sample size of 12 (but then they will happily accept the results from smaller studies if they like the results). I see no issues with the sample size.
The results are pretty clear: running economy was better in the softer shoes (I am a little surprised by this).
Probably the most telling result for me was not that conclusion, but the 10 of 12 (treadmill) and 9 of 12 (overground) had better economy; but this also means 2 of 10 (treadmill) and 3 of 12 (overground) were less economical. While the results of this study show a systematic response, this confirms that there is a subject specific response as well as meaning we can not necessarily make blanket recommendations on shoe condition and running economy. We already know that softer shoes do not increase the injury rates, so the softer shoes are not the evil that the evangelists were and are painting them.
As always, I go where the evidence takes me until convinced otherwise, and cushioned running shoes are not evil.