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From Fellrnr.com, Running tips
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[[Running Economy]] is how much energy it takes you to run. The better your economy, the faster and further you can run. Running economy is obviously determined to some extent by biomechanical efficiency. Changes in things like arm movement and the amount of "bounce" can have a direct impact on running economy. However there is some evidence that biochemical changes may have a significant impact on running economy. For instance slow twitch [[Muscle|muscles]] require less oxygen for the same level of work as fast which muscles do. Running Economy can vary by as much as 30% between runners of a similar [[VO2max|V̇O<sub>2</sub>max]]<ref name="Daniels-1985"/>. The two charts below show the [[VO2max|V̇O<sub>2</sub>max]] and running economy of Paula Radcliffe over a 10 year period<ref name="Jones2006"/>. Over that time Paula Radcliffe's race performance dramatically improved even though her [[VO2max|V̇O<sub>2</sub>max]] did not. This suggests that for elite athletes at least, improvements in running economy are critical.
{| class="wikitable"
Studies have consistently shown that heavier shoes reduce running economy<ref name="LussianaFabre2013"/><ref name="Burkett-1985"/><ref name="Sobhani-2014"/><ref name="Wierzbinski-2011"/>. Each 100g/3.5oz added to the weight of each shoe reduces running economy by about 1%<ref name="Franz-2012"/><ref name="Wierzbinski-2011"/><ref name="Frederick 1985"/><ref name="Frederick-1984"/>.
==Shoe Cushioning==
[[File:Reeves-2014-ShoeMass-RE.jpg|right|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|V̇O<sub>2</sub>max]](the shapes) and the vertical axis is the change in RE compared with barefoot.]]
The results of studies that have compared barefoot and shod running (or running in un-cushioned and cushioned shoes) have provided conflicting information. Some studies show that running economy is worse when wearing shoes, with the bulk of the detrimental effect explained by the shoe weight. However, other studies have shown that the cushioning provided by shoes can compensate for the reduction in running economy due to shoe weight, and sometimes the shoes can actually be provide better economy than barefoot. I believe that the key to understanding this conflict lies in the type of running a surface that is used by the study. Not surprisingly, if a study uses a cushioned treadmill, the cushioning provided by the shoe does not confer any additional advantage over the barefoot condition. Of the 11 studies I found, 3 of the 4 studies using cushioned treadmills showed no improvement in running economy for shoe cushioning, while the 4 studies using un-cushioned treadmills and one using a cushioned treadmill showed an improvement for shoe cushioning. There were three studies that did not give sufficient information to determine the type of treadmill, and two showed no improvement while the remainder did. '''I conclude that a well cushioned running shoe can improve Running Economy by an estimated 2-3.5% compared with a weight matched un-cushioned shoe'''. In practice, most shoes will have a beneficial impact on Running Economy due to cushioning and a negative impact due to their weight.
* Studies on cushioned treadmills
* 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 lower 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
** 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 [http://www.zebris.de/english/medizin/medizin-kraftverteilungsmessung-fdmt.php?navanchor=1010043 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.
==Heel Rise (drop)==
The typical running shoe has a sole that is around 10mm thicker at the heel than the forefoot, something that is typically called "drop" or "pitch". Currently the available research in this area is extremely limited.
* A study looked at the running economy of Newton running shoes that have "actuator lugs" on the forefoot<ref name="MoranGreer2013"/>. The study used identical shoes as controls with the lugs removed. The control shoes were slightly lighter (0.5oz/15g), and had 5mm more drop. The subjects were 12 highly trained male runners, 5 with a midfoot strike, and 7 with a rear foot strike. The study found that the actuator lugs resulted in a ~1% improvement in running economy, even though the shoes were slightly heavier. The improvement could be due to the additional forefoot cushioning, the reduced drop, or something specific to the forefoot cushioning in the actuator lugs. (Having run in Newton shoes, the forefoot cushioning does not feel any different to other cushioning systems, though the lack of material under the toes does change the final push off.)
* An undergraduate thesis showed no difference in running economy with subjects wearing shoes with 0mm drop, 4mm drop, and their usual running shoes (12-14mm)<ref name="Brown2013"/>.
* In one of the more bizarre bits of research, a comparison of running shoes and stiletto high heeled dress shoes (4.5cm and 7cm heels) showed that the running shoes were more economic<ref name="GuLi2013"/>.
==Other Shoe Characteristics==
There are a handful of studies that have looked at other shoe characteristics, there is insufficient information to reach any conclusions.
=Fatigue=
A short (30 minute) high intensity run does not change economy<ref name="Morgan-1990"/>, but economy deteriorates during a marathon run, possibly due to muscle damage and the need for greater neurological muscle activation to produce the force required to maintain pace<ref name="KyrPullinen2000"/>. However, a marathon run does not significantly change running biomechanics such as ground contact time<ref name="NicolKomi2007"/>.
=Glycogen depletion & Fat Burning=
Because burning fat requires more oxygen than carbohydrate, the switch to fat burning due to [[Glycogen]] Depletion means more oxygen is required. This does not directly change running economy as the energy required remains similar<ref name="KyrPullinen2000"/>. However, breathing rate becomes higher to supply the required oxygen, and the amount of oxygen extracted in each breath is lower, further driving the breathing rate.
=Heat=TBD.=DOMS=[[Delayed Onset Muscle Soreness]] reduces running economy<ref name="BraunDutto2003"/><ref name="Smith-1992"/>.=Flexibility=[[File:Standing External Hip Rotation.jpg|right|thumb|200px|Greater Standing External Hip Rotation reduces running economy.]]Greater flexibility reduces running economy. Runners with greater standing external hip rotation and dorsiflexion of the foot have poorer running economy<ref name="Craib-1996"/>. (Dorsiflexion of the foot is bending the ankle so the toes move towards the shin, which is what happens when you do a calf stretch. Standing External Hip Rotation is shown above.) Another study showed that greater overall flexibility is associated with poorer economy, with the most flexible third of the studied group using 9% more energy than the least flexible third<ref name="Gleim-1990"/>.* '''Stretching Programs'''. Most studies show that [[Stretching]] programs do not reduce running economy<ref name="Nelson-2001"/><ref name="Godges-1993"/>.* '''Stretching before running'''. One study<ref name="Wilson-2010"/> has shown that stretching directly before running reduces performance and running economy, but most studies indicate no impact<ref name="AllisonBailey2008"/><ref name="Hayes-2007"/>, even though the stretching impairs other muscular functioning. (One study on subjects with limited hip range of motion showed that stretching before running improved running economy<ref name="Godges-1989"/>, but the subjects were only tested with 4 minutes of running, and a steady state requires 4-15 minutes<ref name="Morgan-1989"/>). =Body weight and fat percentage=* '''Body Mass'''. Greater body mass is associated with better running economy<ref name="Bourdin-1993"/><ref name="Bergh-1991"/>. This may be because larger individuals can store more elastic energy on each step to reduce their energy consumption<ref name="Taboga-2012"/>.* '''Body Fat'''. Perhaps surprisingly, obese individuals have similar running economy as leaner individuals<ref name="Taboga-2012"/>. Remember that running economy is energy used divided by weight. So the heavier you are, the more energy required overall, and more body fat results in a lower power output. So being overweight reduces your fitness Running Dynamics (aerobic capacityrationalize) but not your running economy. =Gender=Women may improve their running economy in response to training more effectively than men<ref name="Bourdin-1993"/>. =Muscle Fiber Types=Fast twitch [[Muscle]] fibers require more energy to provide contraction than slow twitch muscles<ref name="Huxley-1974"/><ref name="Horowitz-1994"/><ref name="Coyle-1992"/>, so a runner with a higher proportion of slow twitch fibers will have better running economy. =Running Dynamics=
* '''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"/>.
* '''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"/>.
* '''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'''. 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"/>. The energy taken to run is mostly taken with supporting the weight of the body.
** Factors related to top running speed and economy<ref name="Nummela-2007"/>
*** RE correlated to longer GCT
*** GCT measured at 5.8-6.6 m/s (4:37-4:04), then 3.3-5.56 m/s
*** One study showed that longer GCT was correlated to better RE, but that study measured RW at 3.9 m/s (6:50 min/mile), and the correlation with longer GCT was only seen at speeds between 5.8-6.6 m/s (4:37-4:04 min/mile), rather radically faster.
** Neuromuscular characteristics and muscle power as determinants of 5-km running performance
*** 3.67 m•s m·s – 7:18*** 4.17 m•s m·s 6:26
*** CV = 4.5, 6:00
*** Furthermore, REtrack2 correlated with the mean CT of constant velocity laps during the 5K (r = 0.64, P < 0.001).
*** REtread was measured as a steady-state oxygen uptake (V•O2V·O2, U mL•kgmL·kg-'''0.75'''•min·min-1) (38)
*** Longer GCT has greater VO2 cost (poorer RE)
** Explosive-strength training improves 5-km running time by improving running economy and muscle power
** No difference in running economy, but higher work for FFS suggesting more elastic storage<ref name="Ardigò-1995"/>
** No difference between FFS/MFS and RFS except for habitual RFS doing FFS had a lower economy<ref name="GruberUmberger2013"/>
** Subelite RFS is more economic than MFS. Cadence same, but contact time greater in RFS<ref name="Ogueta-Alday-2014"/>.
=Body weight and fat percentage (intro)=
* '''Body Mass'''. Greater body mass is associated with better running economy<ref name="Bourdin-1993"/><ref name="Bergh-1991"/>. This may be because larger individuals can store more elastic energy on each step to reduce their energy consumption<ref name="Taboga-2012"/>.
* '''Body Fat'''. Perhaps surprisingly, obese individuals have similar running economy as leaner individuals<ref name="Taboga-2012"/>. Remember that running economy is energy used divided by weight. So the heavier you are, the more energy required overall, and more body fat results in a lower power output. So being overweight reduces your fitness (aerobic capacity) but not your running economy.
=Heat (TBD)=
TBD.
=DOMS=
[[Delayed Onset Muscle Soreness]] reduces running economy<ref name="BraunDutto2003"/><ref name="Smith-1992"/>.
=Flexibility=
[[File:Standing External Hip Rotation.jpg|right|thumb|200px|Greater Standing External Hip Rotation reduces running economy.]]
Greater flexibility reduces running economy. Runners with greater standing external hip rotation and dorsiflexion of the foot have poorer running economy<ref name="Craib-1996"/>. (Dorsiflexion of the foot is bending the ankle so the toes move towards the shin, which is what happens when you do a calf stretch. Standing External Hip Rotation is shown above.) Another study showed that greater overall flexibility is associated with poorer economy, with the most flexible third of the studied group using 9% more energy than the least flexible third<ref name="Gleim-1990"/>.
* '''Stretching Programs'''. Most studies show that [[Stretching]] programs do not reduce running economy<ref name="Nelson-2001"/><ref name="Godges-1993"/>.
* '''Stretching before running'''. One study<ref name="Wilson-2010"/> has shown that stretching directly before running reduces performance and running economy, but most studies indicate no impact<ref name="AllisonBailey2008"/><ref name="Hayes-2007"/>, even though the stretching impairs other muscular functioning. (One study on subjects with limited hip range of motion showed that stretching before running improved running economy<ref name="Godges-1989"/>, but the subjects were only tested with 4 minutes of running, and a steady state requires 4-15 minutes<ref name="Morgan-1989"/>).
=Breathing (TBD)=
It takes energy to breathe, and this can have a significant impact on running economy.
=Gender =
Women may improve their running economy in response to training more effectively than men<ref name="Bourdin-1993"/>.
=Muscle Fiber Types=
Fast twitch [[Muscle]] fibers require more energy to provide contraction than slow twitch muscles<ref name="Huxley-1974"/><ref name="Horowitz-1994"/><ref name="Coyle-1992"/>, so a runner with a higher proportion of slow twitch fibers will have better running economy.
=Magnesium=
They is evidence that [[Magnesium]] deficiency increases the energy cost of exercise<ref name="Lukaski-2002"/>.
<ref name="Lukaski-2002">HC. Lukaski, FH. Nielsen, Dietary magnesium depletion affects metabolic responses during submaximal exercise in postmenopausal women., J Nutr, volume 132, issue 5, pages 930-5, May 2002, PMID [http://www.ncbi.nlm.nih.gov/pubmed/11983816 11983816]</ref>
<ref name="Tung-2014">KD. Tung, JR. Franz, R. Kram, A test of the metabolic cost of cushioning hypothesis during unshod and shod running., Med Sci Sports Exerc, volume 46, issue 2, pages 324-9, Feb 2014, doi [http://dx.doi.org/10.1249/MSS.0b013e3182a63b81 10.1249/MSS.0b013e3182a63b81], PMID [http://www.ncbi.nlm.nih.gov/pubmed/24441213 24441213]</ref>
<ref name="Tung-2014-PC">From email communication with Kryztopher D. Tung.</ref>
<ref name="Roy-2006">JP. Roy, DJ. Stefanyshyn, Shoe midsole longitudinal bending stiffness and running economy, joint energy, and EMG., Med Sci Sports Exerc, volume 38, issue 3, pages 562-9, Mar 2006, doi [http://dx.doi.org/10.1249/01.mss.0000193562.22001.e8 10.1249/01.mss.0000193562.22001.e8], PMID [http://www.ncbi.nlm.nih.gov/pubmed/16540846 16540846]</ref>
<ref name="LuoStergiou2009">Geng Luo, Pro Stergiou, Jay Worobets, Benno Nigg, Darren Stefanyshyn, Improved footwear comfort reduces oxygen consumption during running, Footwear Science, volume 1, issue 1, 2009, pages 25–29, ISSN [http://www.worldcat.org/issn/1942-4280 1942-4280], doi [http://dx.doi.org/10.1080/19424280902993001 10.1080/19424280902993001]</ref>
<ref name="woodway.com">WOODWAY PPS Ultimate Medical Treadmill, http://medical.woodway.com/cardiac_rehab/cardiac_rehab_pps.html, Accessed on 19 October 2014</ref>
<ref name="Morgan-1994">DW. Morgan, MW. Craib, GS. Krahenbuhl, K. Woodall, S. Jordan, K. Filarski, C. Burleson, T. Williams, Daily variability in running economy among well-trained male and female distance runners., Res Q Exerc Sport, volume 65, issue 1, pages 72-7, Mar 1994, doi [http://dx.doi.org/10.1080/02701367.1994.10762210 10.1080/02701367.1994.10762210], PMID [http://www.ncbi.nlm.nih.gov/pubmed/8184214 8184214]</ref>
<ref name="Ogueta-Alday-2014">A. Ogueta-Alday, JA. Rodríguez-Marroyo, J. García-López, Rearfoot striking runners are more economical than midfoot strikers., Med Sci Sports Exerc, volume 46, issue 3, pages 580-5, Mar 2014, doi [http://dx.doi.org/10.1249/MSS.0000000000000139 10.1249/MSS.0000000000000139], PMID [http://www.ncbi.nlm.nih.gov/pubmed/24002340 24002340]</ref>
<ref name="Nummela-2007">A. Nummela, T. Keränen, LO. Mikkelsson, Factors related to top running speed and economy., Int J Sports Med, volume 28, issue 8, pages 655-61, Aug 2007, doi [http://dx.doi.org/10.1055/s-2007-964896 10.1055/s-2007-964896], PMID [http://www.ncbi.nlm.nih.gov/pubmed/17549657 17549657]</ref>
<ref name="MoranGreer2013">Matthew F. Moran, Beau K. Greer, Influence of midsole 'actuator lugs' on running economy in trained distance runners, Footwear Science, volume 5, issue 2, 2013, pages 91–99, ISSN [http://www.worldcat.org/issn/1942-4280 1942-4280], doi [http://dx.doi.org/10.1080/19424280.2013.792878 10.1080/19424280.2013.792878]</ref>
<ref name="GuLi2013">Effect of Shoes' Heel Height on the Energy Cost during Jogging, Y.D. Gu and Z.Y. Li, Research Journal of Applied Sciences, Engineering and Technology July 15, 2013</ref>
<ref name="Brown2013">The Acute Effect of Heel to Toe Drop on Running Economy. Brown, Harrison and Silva, Robert (2013). Undergraduate thesis, Fort Lewis College</ref>
</references>
