Purpose: 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 due to 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.
Methods: 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 which had a rigid deck. 12 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[spacing dot above]O2 and V[spacing dot above]CO2 to calculate the metabolic power demand and used a RMANOVA to compare between conditions.
Results: Compared to running unshod on the normal belt, running unshod on the 10mm thick foam required 1.63 +/- 0.67% (mean +/- SD) less metabolic power (p=0.034) but running on the 20mm 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.
Conclusions: On average, surface and shoe cushioning reduce the metabolic power required for submaximal running.
(C) 2013 American College of Sports Medicine