Publications

Background: Advanced footwear technology (AFT) generally improves running economy (RE) measures on average by 4%, although considerable interindividual variability exists. We aimed to explore this interindividual variability in RE response to AFT compared to a CONTROL shoe and identify potential predictors of this variability. Specifically, differences in participant characteristics (e.g., age, sex, anthropometrics, running experience and speed, prior AFT use, V̇O2 peak, lower-limb neuromuscular performance, passive stiffness, running biomechanics, and perceptual measures) between above-threshold and below-threshold responders (∆RE threshold: 2.5%) and how these measures related to RE responses were explored.

Methods: Sixty-four participants (50% female) attended two laboratory sessions at the University of Waikato Sports Science Laboratory in Cambridge, New Zealand, between 10 October 2024 and 7 February 2025. The first session collected baseline information and participant characteristics related to anthropometric, stiffness, strength, and V̇O2 peak. The second session assessed RE variables at 70% of a maximal aerobic test (i.e., V̇O2 peak) speed in two randomised shoe conditions: Salomon S/Lab Phantasm 2 (AFT) and Salomon Aero Glide 2 (CONTROL).

Results: AFT significantly improved RE (4.13 ± 1.6%, range: − 2.62% [detrimental] to 11.01% [beneficial]) based on change in oxygen consumption. Significant differences between above-threshold (n = 53) and below-threshold (n = 11) responders were limited to the former exhibiting greater gastrocnemius medialis (GM) stiffness normalised to leg length (mean difference = 33.4 N·m−2, Hedges’ g = 0.86 [0.20, 1.51], p = 0.046). GM stiffness normalised to leg length (B = 0.014 N·m−2, p = 0.015) and navicular drop (B = 1.849 cm, p = 0.028) significantly predicted RE responses in our regression model (R2 = 0.273), with greater stiffness (r = 0.35 [0.11, 0.55], p = 0.005) and navicular drop (r = 0.31 [0.07, 0.52], p = 0.012) associated with more beneficial AFT responses.

Conclusion: AFT enhanced RE in most runners, with few factors explaining the interindividual variance observed.

Keywords: athletic performance, biomechanical phenomena, interindividual variability, neuromuscular function, oxygen consumption

Overall, AFT footwear improved RE, although individual responses varied. Our findings indicate there may be some anatomical and neuromuscular factors mediating this interindividual variation, specifically related to muscle–tendon stiffness, foot structure, and ankle geometry. Greater GM stiffness normalised to leg length and greater navicular drop appeared to be the strongest correlates of improved RE response to AFT, whereas weaker plantarflexion strength and greater ankle gear ratio showed weaker relationships and were not retained in the regression model. These results suggest that individual mechanical and structural characteristics may partly influence the extent to which runners benefit from AFT. Understanding these variables may help inform more personalised footwear recommendations and training strategies to optimise RE benefits from AFT. Nonetheless, a large proportion of the interindividual response remains unexplained, and corroborating studies are needed to confirm the generalisation of these findings.