Biomechanical Factors Associated with Intraindividual Differences in Running Economy Across Advanced Footwear Technology Models in Long-Distance Runners.

BACKGROUND

Advanced footwear technology (AFT) can enhance long-distance running performance by improving running economy (RE). However, the range of the individual improvements is large. Different intra-individual responses in running biomechanics may account for some of the variation. Thus, this randomized within-subject crossover study aimed to identify biomechanical factors associated with changes in RE when running with different AFT models.

METHODS

Twenty-two trained long-distance runners (50% female) ran multiple 5-minute running bouts at their season's best marathon pace (15.0 ± 2.3 km⸱h- 1) while wearing three standardized AFT models (Nike Air Zoom Alphafly Next% 2, Puma Fast-R Nitro Elite v1, Asics Metaspeed Sky+). During each condition, gas exchange data and three-dimensional kinematics and spatiotemporal variables were acquired. RE was determined as the energetic cost of transport. We used two complementary model selection strategies (Akaike Information Criterion model averaging and least absolute shrinkage and selection operator) to identify biomechanical parameters associated with intra-individual differences in RE, and a repeated measures ANOVA to compare RE between shoes at the group level.

RESULTS

Across shoe conditions, shorter ground contact time was significantly associated with lower energetic cost of transport (β = 0.025, 95% CI [0.010, 0.040], t(42) = 3.33, p = 0.002), reflecting a ~ 1% improvement in RE per 4 ms decrease. We did not find group-level differences in RE between shoe conditions (p = 0.246).

CONCLUSIONS

AFT models that reduced runners' individual ground contact time were associated with improved RE. This effect appears to depend on the individual athlete-shoe interaction since no single AFT model stood out as an overall optimum. These findings can help determine optimal footwear for athletes. Future studies should investigate the interaction of AFT properties and individual biomechanics to identify further RE improvements through footwear individualization.