Arch Stiffness Does Not Determine Running Economy in Recreational Runners

The primary purpose of this study was to determine the relationship between foot length, arch stiffness, and running economy in recreational runner at low running velocities. Sixteen trained endurance (age 20.5 ± 0.4 yrs, height 172 ± 1.8 cm, and mass 68.53 ± 2.40 kg) athletes had their foot anthropometrics and running economy measured. Foot anthropometrics including Foot Length (FL), Arch Stiffness Index (ASI), and Achilles Tendon Moment Arm Length (ATML) were assessed. Subjects then completed a maximal oxygen consumption (VO_2max) test and running economy (RE) assessment. RE was measured as the oxygen consumption during running at velocities of 9.9 km/h and 11.9 km/h at a 1% grade. Data is reported as Mean ± SE, and the relationship between foot anthropometrics and running economy was assessed with linear regression (α = 0.05). Results: Absolute and relative VO_2max values were 3.68 ± 0.19 L/min and 52.96 ± 1.51 mL/kg/min. ASI was 1513 ± 174.27 A.U. with a standing foot length of 25.41 ± 0.4 cm. Subject oxygen consumption at 9.9 km/h and 11.9 km/h was 34.9 ± 0.80 mL/kg/min and 41.02 ± 0.82 mL/kg/min, respectively. There was no correlation between ASI, FL, AHI, and RE (p > 0.05). Arch stiffness and Achilles tendon moment arm do not determine running economy. Therefore, running economy may be impacted by other physiological and biomechanical factors at low running velocities.