Changes

[[File:Paula Radciffe NYC Marathon 2008 cropped.jpg|right|thumb|300px150px|Paula Radcliffe, the holder of the women's world record for the marathon (2:15:25) has gained much of her improvement through greater Running Economy.]]

* '''===Studies on cushioned treadmills'''. ===Most studies tend to use cushioned treadmills, as these are the most commonly available.** A thesis study showed that barefoot is more economic than shoed (New Balance M1500, 344-368g/shoe), but the same as shod when compensating for shoe mass<ref name="Flaherty-1994"/>. The barefoot condition had a greater [[Cadence]] than shod. The treadmill (Marquette model 1900) was cushioned.** Habitually FFS runners are 2.4% more efficient in minimally shod (FiveFingers with) than cushioned (GEL-Cumulus 10) shoes at 9 min/mile pace and with weights to ensure equal mass<ref name="Perl-2012"/>. This study used a Vision T9250 treadmill that is cushioned, with a reputable reviewer rating as 6.8/10 for cushioning<ref name="treadmilldoctor.com"/>.** A study compared barefoot (BFT), minimally shod (MS), and shod (SH) showed that BFT was 2.6-5.1% more efficient than SH<ref name="MooreJones2014"/>. The study also compared MS at the [[Cadence]] of BFT (165) and the cadence of SH (160), with an improvement only seen at the lower cadence. The participants had no prior barefoot or minimal running experience, and no adjustment was made for shoe mass. However, this study used a Woodway PPS treadmill with the manufacture claim that "Our patented Slat Belt running surface helps absorbs more of the impact than any other treadmill(<ref name="woodway.com"/>)".** A study comparing barefoot running with the participants using their normal running shoes showed that barefoot condition had a 4.4% improvement in running economy<ref name="Reeves-2014"/>. However, 80% of the change in running economy could be explained by shoe mass. In fact, the slope of the line between shoe mass and running economy predicts that a shoe weighing 9.2oz/260g would have the same running economy has barefoot. The shoes used weighed between 8.5-15oz (239-430g). Interestingly while running economy improved, [[VO2max|V̇O₂max]] did not. The treadmill used was a WoodWay Pro-XL, a highly cushioned "slatted" treadmill similar to the one noted above.* [[File:Reeves-2014-ShoeMass-RE.jpg|center|thumb|300px|Shoe mass against running economy<ref name="Reeves-2014"/>.Even on a cushioned treadmill, it appears that shoe cushioning can provide an improvement in running economy. The tests were performed at paces corresponding to various percentages of [[VO2max|V̇O₂max]] (the shapes) and the vertical axis is the change in RE compared with barefoot. ]]===Studies on un-cushioned treadmills. ===** Running in lightweight (150g/5.3oz, Nike Mayfly) shoes was 2% more efficient than barefoot<ref name="Franz-2012"/>. The study used runners with a midfoot [[Foot Strike]] and an un-cushioned treadmill (Quinton 1860). ** A thesis study showed that running in lightweight shoes (Nike Mayfly) was 3.4% more efficient than weight matched barefoot, and 2.1% more efficient than barefoot<ref name="Wierzbinski-2011"/>. The study used runners with a midfoot [[Foot Strike]] and an un-cushioned treadmill (Quinton 1860). When the weight of the Nike Mayfly shoes was doubled using weights, the running economy was still better than barefoot. The study also added EVA foam to the treadmill surface, but this did not change the running economy of barefoot running. However, the cushioning was added in slabs, and participants noted that the gaps felt "like running on a trail". ** Running barefoot and in Nike 3.0 shoes had no difference in running economy on an un-cushioned treadmill (Quinton 1860)<ref name="Tung-2014"/>. However, adding 10mm of cushioning to the treadmill improved barefoot running economy by 1.9%<ref name="Tung-2014"/>. Using 20mm cushioning made no further improvement over 10mm. The cushioning was provided by EVA foam used in running shoes. (The EVA foam was fairly soft, measuring 52-58 on the Asker Type C scale<ref name="Tung-2014-PC"/>. That's about 27-33 on the Shore A scale.)** A comparison of barefoot and shoes weighing 150g and 350g showed the same running economy in barefoot and 150g shoes, but 3.6% lower running economy in 350g shoes<ref name="Divert-2008"/>. The treadmill used (ADAL 3D, HEF-Tecmachine) appears to be un-cushioned. This study also showed that compared with barefoot, shoes reduced the total energy required to run (work) without changing V̇O<ref name="Divert-2008"/>, suggesting that barefoot is using more elastic energy, further suggesting that the barefoot condition in this study uses forefoot strike<ref name="Ardigò-1995"/>.* '''===Unknown Treadmill'''. ===Sadly, many studies don't explicitly state the type of treadmill used.** Barefoot was 2.0% more economic than shod on a treadmill and 5.7% more economic on an indoor track<ref name="Hanson-2011"/>. However, the type of treadmill and indoor track was not described and may have been cushioned. No indication was given of the type or weight of the shoes used. ** Barefoot was 1.3% more efficient than running in 340g shoes, while Vibram FiveFingers was 2.8% more efficient<ref name="Squadrone-2009"/>. The [[Cadence]] was 91.2 barefoot, 88.3 in FiveFingers, and 86.0 in shoes. While it seems strange that the FiveFingers were more efficient than barefoot, I suspect this is likely to be a statistical anomaly due to the small sample size (8 runners). The runners were all experienced in barefoot running. It is unclear if the Zebris FDM-T treadmill is cushioned or not. ** A study using Nike Air shoes showed an average 2.4% improvement in running economy compared with firmer shoes of a similar weight<ref name="Frederick 1986"/>. The improvement in running the economy varied by individual, between 0.5% and 6%, SD=1.8%. No details of the type of treadmill used were recorded.

==Shoe Flexibility==

* '''==Cadence'''. ==A review of the scientific studies showed consistently that an increased [[Cadence]] reduces shock at the hip, knee, and ankle, vertical oscillation, and ground contact time<ref name="SchubertKempf2013"/>. One study calculated that Cadence is 28% of the variation due to biomechanical differences<ref name="TartarugaBrisswalter2012"/>.* '''==Balance and step width'''. ==Maintaining side to side balance is estimated to cost 2% of the energy of running<ref name="ArellanoKram2011"/>. This may be due to step width, as increasing step width can reduce running economy by 11%<ref name="Arellano-2011"/>. [[File:Step Width.jpg|rightcenter|thumb|200px150px|The blue line is the center line of the body and the red line indicates the center of the foot placement. The distance between the two lines is the step width.]]* '''==Arm Swing'''. ==While it obviously costs energy to swing the arms while running, this arm swing actually improves running economy<ref name="ArellanoKram2011"/><ref name="Arellano-2011"/>, probably by improving balance. * '''==Ground Contact Time==It'''. It's s a generally believed that the less time a runner spends in contact with the ground, the more efficient they are. However, the scientific evidence is a little patchy. ** Two studies found that a shorter Ground Contact Time was indeed correlated with better Running Economy<ref name="PaavolainenNummela1999"/><ref name="Santos-ConcejeroGranados2013"/>** Plyometric training for 9 weeks improved 5K times, improved running economy and reduced Ground Contact Time<ref name="PaavolainenHakkinen2003"/>. It's unclear if the reduced Ground Contact Time was part of the improvement in either 5K time or running economy, but it is suggestive.** Two studies found no relationship between Ground Contact Time and Running Economy<ref name="HeiseMartin2001"/><ref name="TartarugaBrisswalter2012"/>.** One study found that a longer Ground Contact Time is correlated to a better Running Economy, the opposite of what is generally expected<ref name="Nummela-2007"/>. However, that study measured Running Economy at 3.9 m/s (6:50 min/mile), and the correlation with longer Ground Contact Time was only seen at speeds between 5.8-6.6 m/s (4:37-4:04 min/mile), rather radically faster.** Running to exhaustion may increase Ground Contact Time<ref name="FourchetGirard2015"/>. This may not tell us much about Running Economy, but it's possible that Ground Contact Time might be an indirect measure of fatigue.** In a wide range of animals, from a 32g kangaroo rat to a 140Kg pony, the energy cost of running has been shown to be proportional to the time each foot spends in contact with the ground<ref name="KramTaylor1990"/>. This suggests that the energy taken to run is mostly taken with supporting the weight of the body.* '''==Vertical Oscillation'''. ==It seems obvious that greater Vertical Oscillation is going to be less efficient, but the research is not there to support this. One study noted "The intuitive perception is that oscillation is adversely related to economy" but found no supporting research<ref name="Anderson1996"/>.** Greater vertical impulse on a force plate related to lower RE but noted exceptions to this seem common<ref name="HeiseMartin2001"/>.** In 16 national level runners, greater Vertical Oscillation was associated with improved Running Economy, the opposite of what would be expected<ref name="TartarugaBrisswalter2012"/>. The study found that Vertical Oscillation accounted for 7% of the variation due to biomechanical differences. ** A 1997 study found elite runners have less Vertical Oscillation than sub-elite runners<ref name="CavanaghPollock1977"/>.** Running with exaggerated Vertical Oscillation reduces Running Economy<ref name=" Tseh2008"/>. This suggests that it's possible to use excessive bounce to intentionally compromise your running, and might indicate that some runners could have a problematic level of Vertical Oscillation, but there is no clear evidence to indicate that's the case.** A study of 31 runners found that there was a non-significant relationship between increased Vertical Oscillation and reduced Running Economy, with the most economic runners having a Vertical Oscillation of 9.1cm and the least economic having 9.6cm<ref name="Cavanagh1987"/>.** Running to exhaustion may increase Vertical Oscillation<ref name="FourchetGirard2015"/>, which might make Vertical Oscillation a metric for evaluating fatigue.** Vertical Oscillation tends to decrease with increased Cadence<ref name="HalvorsenEriksson2012"/>. This makes perfect sense from a simplistic model of running, as a higher cadence means that each stride is shorter, so less time is spent in the air where the runner is in a ballistic curve. This relationship can confuse the analysis of Running Economy, as it's easy to attribute changes in Cadence to Vertical Oscillation, or Ground Contact Time.** Feedback to reduce Vertical Oscillation resulted in impaired Running Economy<ref name="HalvorsenEriksson2012"/>. The study used real-time feedback to encourage runners to reduce their Vertical Oscillation, but the study lasted a relatively short time. It's possible that the impaired Running Economy was a result of the initial change in biomechanics rather than indicating that reduced Vertical Oscillation is actually a bad thing. Of course, the other interpretation is that there is an optimal level of Vertical Oscillation and attempting to reduce it is actually a bad thing.Vertical Oscillation and attempting to reduce it is actually a bad thing.==Braking==Another intuitively obvious factor in running economy is breaking. After all, anything that slows a runner seems likely to reduce their running economy. There are three obvious places to measure breaking; the foot, the ground, and the body. A runner's foot has to decelerate so that there is no horizontal movement when it's in contact with the ground, and then accelerate to be faster than the body to move ahead for the next footfall. If the foot has decelerated so that there is no horizontal movement prior to the footfall, then you'd expect no braking force to be detected in the ground, whereas if the foot is still moving forward, there would be a braking force detected. The third place to measure breaking is the body (or center of mass), which may also vary in horizontal velocity. It seems a reasonable that variations in horizontal velocity of the body would reduce running economy.* A study of 17 runners found that the braking force detected on the ground explained most of the variation in running economy<ref name=" KyröläinenBelli2001"/>.* A study of 11 elite runners found that there was a statistically significant correlation between the sum of the peak horizontal and vertical forces and running economy, with lower forces being more economical<ref name="StørenHelgerud2011"/>. However, the study did report on horizontal forces alone, or the total energy involved in the breaking.I've not found any research covering braking forces on the body, which would seem to be a natural subject of inquiry.==Foot strike==* '''Foot strike. '''It's often assumed that a forefoot landing is more efficient than a rear foot landing, but there's no clear evidence to support that.** A study found that while there was no difference in Running Economy between different foot strike types, there was a higher work produced with Forefoot Strike, suggesting more elastic storage<ref name="Ardigò-1995"/>.** A study looked at runners with different foot strike patterns and compared them running with their habitual stride and intentionally modifying to an alternative foot strike<ref name="GruberUmberger2013"/>. The study found no differences with the exception of rear foot strike runners changing to a forefoot strike.** Sub-elite rear foot strike runners are more economic than midfoot strike, and while a cadence was the same the rearfoot runners had a higher Ground Contact Time<ref name="Ogueta-Alday-2014"/>.