A Test of the Metabolic Cost of Cushioning Hypothesis during Unshod and Shod Running

Medicine and science in sports and exercise (Impact Factor: 4.46). 02/2014; 46(2):324-329. DOI: 10.1249/MSS.0b013e3182a63b81
Source: PubMed

ABSTRACT This study aimed to investigate the effects of surface and shoe cushioning on the metabolic cost of running. In running, the leg muscles generate force to cushion the impact with the ground. External cushioning (surfaces or shoes) may reduce the muscular effort needed for cushioning and thus reduce metabolic cost. Our primary hypothesis was that the metabolic cost of unshod running would decrease with a more cushioned running surface. We also hypothesized that because of the counteracting effects of shoe cushioning and mass, unshod running on a hard surface would have approximately the same metabolic cost as running in lightweight, cushioned shoes.
To test these hypotheses, we attached 10- and 20-mm-thick slats of the same foam cushioning used in running shoe midsoles to the belt of a treadmill that had a rigid deck. Twelve subjects who preferred a midfoot strike pattern and had substantial barefoot/minimalist running experience ran without shoes on the normal treadmill belt and on each thickness of foam. They also ran with lightweight, cushioned shoes on the normal belt. We collected V˙O2 and V˙CO2 to calculate the metabolic power demand and used a repeated-measures ANOVA to compare between conditions.
Compared to running unshod on the normal belt, running unshod on the 10-mm-thick foam required 1.63% ± 0.67% (mean ± SD) less metabolic power (P = 0.034) but running on the 20-mm-thick foam had no significant metabolic effect. Running with and without shoes on the normal belt had similar metabolic power demands, likely because the beneficial energetic effects of cushioning counterbalanced the detrimental effects of shoe mass.
On average, surface and shoe cushioning reduce the metabolic power required for submaximal running.

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    ABSTRACT: Background The effect of footwear on running economy has been investigated in numerous studies. However, no systematic review and meta-analysis has synthesised the available literature and the effect of footwear on running performance is not known. Objective The aim of this systematic review and meta-analysis was to investigate the effect of footwear on run-ning performance and running economy in distance run-ners, by reviewing controlled trials that compare different footwear conditions or compare footwear with barefoot. Methods The Web of Science, Scopus, MEDLINE, CENTRAL (Cochrane Central Register of Controlled Tri-als), EMBASE, AMED (Allied and Complementary Medicine), CINAHL and SPORTDiscus databases were searched from inception up until April 2014. Included articles reported on controlled trials that examined the effects of footwear or footwear characteristics (including shoe mass, cushioning, motion control, longitudinal bend-ing stiffness, midsole viscoelasticity, drop height and comfort) on running performance or running economy and were published in a peer-reviewed journal. Results Of the 1,044 records retrieved, 19 studies were included in the systematic review and 14 studies were included in the meta-analysis. No studies were identified that reported effects on running performance. Individual studies reported significant, but trivial, beneficial effects on running economy for comfortable and stiff-soled shoes [standardised mean difference (SMD) \0.12; P \ 0.05), a significant small beneficial effect on running economy for cushioned shoes (SMD = 0.37; P \ 0.05) and a significant moderate beneficial effect on running economy for training in minimalist shoes (SMD = 0.79; P \ 0.05). Meta-ana-lysis found significant small beneficial effects on running economy for light shoes and barefoot compared with heavy shoes (SMD \ 0.34; P \ 0.01) and for minimalist shoes compared with conventional shoes (SMD = 0.29; P \ 0.01). A significant positive association between shoe mass and metabolic cost of running was identified (P \ 0.01). Footwear with a combined shoe mass less than 440 g per pair had no detrimental effect on running economy. Conclusions Certain models of footwear and footwear characteristics can improve running economy. Future research in footwear performance should include measures of running performance. Key Points Running shoes with greater shoe cushioning, greater longitudinal shoe stiffness and greater shoe comfort were associated with improved running economy. Running in light shoes or running barefoot reduced metabolic cost compared with running in heavy shoes but there was no difference in metabolic cost between running in light shoes and running barefoot. No studies have investigated the effect of footwear on running performance measured using a time-trial or time-to-exhaustion test.
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    Journal of Experimental Biology 07/2014; 217(Pt 14):2456-61. DOI:10.1242/jeb.100420 · 3.00 Impact Factor
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May 31, 2014