Effects of Foot Orthotics on Running Economy: Methodological Considerations

Abstract Objective The purpose of the study was to collect preliminary data to address methodological considerations that may impact subject-specific reactions to foot orthotics during running. Methods Six endurance-trained recreational runners recruited from a chiropractic college campus wore their preferred running shoes and then inserted either their custom-made orthotics during 1 testing session or their shoe-fitted insoles during the other testing session. Comfort perception was measured for each footwear condition. Measurements of oxygen consumption (V o2 ) at several moderate exercise intensities, to mimic recreational running, generated an individual's economy-of-running line. Predicted running velocity at V o2max (vV o2max ) was calculated as an index of endurance performance. Lower extremity muscle activity was recorded. Descriptive statistics, a repeated-measures analysis of variance model, and a paired t test were used to document any systematic changes in running economy, lower extremity muscle activities, and vV o2max within and across subjects as a function of footwear conditions. Results Decreases in V o2 at several moderate exercise intensities ( F(1,5)footwear = 10.37, P = .023) and increases in vV o2max ( t5 = 4.20, P = .008) occurred in all 6 subjects while wearing their orthotic intervention vs their shoe-fitted insoles. There were no consistent changes in lower extremity muscle activity. Conclusions Methodological decisions to use a sustained incremental exercise protocol at several moderate exercise intensities and to measure comfort perception of a custom-molded foot orthosis were effective at documenting systematic improvements in running economy among the 6 recreational runners tested. The development of a less physically demanding sustained exercise protocol is necessary to determine underlying neuromuscular mechanisms and/or clinical effectiveness of orthotic interventions.