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From Fellrnr.com, Running tips
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The optimum foot strike is unclear given the available evidence.
* While runners can be categorized as RFS, MFS, FFS, in practice runners vary along a spectrum<ref name="Cavanagh-1980"/>.
* There is Two studies showed no difference in [[Running Economy]] between FFS and RFS<ref name="Perl-2012"/><ref name="Cunningham-2010"/>.* A study compared the [[Running Economy]] of habitually FFS and RFS runners when running both FFS and RFS<ref name="Gruber-2013"/>. The runners were relatively fast, with a typical training pace of 7:15 min/mile and running 28 miles/week. The FFS group actually consisted of both FFS and MFS runners, and there were 14 MFS and only 4 FFS runners in the FFS group, with 19 in the RFS group. Each group was tested at slow (9:00 min/mile), medium (7:40 min/mile) and fast (6:45 min/mile) paces with both FFS and RFS. The results were:** Using their habitual footstrike the FFS were very slightly more efficient at medium and fast speeds, but this was not statistically significant. (Estimating from the graphs, this is ~1 mg/kg/min.)** At the slow and medium speed the FFS group using either FFS or RFS and the RFS group running RFS used the same oxygen, but the RFS group running FFS was less efficient. (So if you're a RFS runner, you're likely to be less efficient when running FFS until you get used to it, at which point you'll be back to your prior efficiency.)** At the fast speed both groups were less efficient with a FFS. ** In nearly all situations a RFS used less a lower percentage of carbohydrate than a RFS, the only exception being the FFS group at slow speeds. (This was only statistically significant at the slow speed.)
* Runners tend to shift from RFS to MFS or FFS as they run faster, with runners becoming predominantly FFS at faster than 4:30 min/mile and predominantly RFS as 5:15 min/mile or slower<ref name="KellerWeisberger1996"/><ref name="NiggBahlsen1987"/>.
* One study found that habitually barefoot endurance runners are predominantly FFS, with some MFS but fewer RFS, though the pace evaluated was quite fast (5:15-4:30 min/mile)<ref name="LiebermanVenkadesan2010"/>. Another study showed that at endurance running speeds, habitually barefoot runners were 83% RFS, 17% MFS and none were FFS<ref name="LuciaHatala2013"/>. At faster speeds, this changed, and at around 5 min/mile pace there were 43% RFS, 43% MFS and 14% FFS, then above 4 min/mile the breakdown changed again to 40% RFS, 60% MFS, and no FFS<ref name="LuciaHatala2013"/>.
<ref name="Heiderscheit-2011"> BC. Heiderscheit, ES. Chumanov, MP. Michalski, CM. Wille, MB. Ryan, Effects of step rate manipulation on joint mechanics during running., Med Sci Sports Exerc, volume 43, issue 2, pages 296-302, Feb 2011, doi [http://dx.doi.org/10.1249/MSS.0b013e3181ebedf4 10.1249/MSS.0b013e3181ebedf4], PMID [http://www.ncbi.nlm.nih.gov/pubmed/20581720 20581720]</ref>
<ref name="Giuliani-2011"> J. Giuliani, B. Masini, C. Alitz, BD. Owens, Barefoot-simulating footwear associated with metatarsal stress injury in 2 runners., Orthopedics, volume 34, issue 7, pages e320-3, Jul 2011, doi [http://dx.doi.org/10.3928/01477447-20110526-25 10.3928/01477447-20110526-25], PMID [http://www.ncbi.nlm.nih.gov/pubmed/21717998 21717998]</ref>
<ref name="Gruber-2013">AH. Gruber, BR. Umberger, B. Braun, J. Hamill, Economy and rate of carbohydrate oxidation during running with rearfoot and forefoot strike patterns., J Appl Physiol, May 2013, doi [http://dx.doi.org/10.1152/japplphysiol.01437.2012 10.1152/japplphysiol.01437.2012], PMID [http://www.ncbi.nlm.nih.gov/pubmed/23681915 23681915]</ref>
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