Advanced Footwear Technology in Distance Running: What We Know, What We Don't Know, and Future Directions.

Over the past decade, running shoes have undergone substantial innovation with the emergence of Advanced Footwear Technology (AFT). Shoes with AFT are typically characterized by highly compliant (deformable) and resilient (high energy return) midsole foams, embedded curved stiffening elements, low mass, and a rockered longitudinal geometry. This expert statement aims to synthesize established knowledge, remaining uncertainties and key directions for future research on AFT in middle- and long-distance running. Current literature demonstrates robust improvements in running economy and performance with AFT, with reported metabolic savings of approximately 2%-4%, and corresponding performance improvements of 1%-3%. These benefits likely arise from a combination of "acute" and possibly "long-term" mechanisms. Proposed acute mechanisms include decreased muscle force production due to higher positive work from energy-returning foams, lower muscle force production to accommodate mechanical running demands due to compliant midsoles, and improved mechanical efficiency associated with greater longitudinal bending stiffness and curved geometry. Importantly, AFT features have a synergistic effect, with the relative importance of each mechanism differing depending on the context. Emerging evidence also suggests potential reductions in muscle damage/inflammation and soreness, which could support better physiological resilience, and higher training volumes/quality. From a biomechanical injury risk perspective, AFT can redistribute loading, potentially increasing metatarsal and tarsal stress while reducing tibia and possibly Achilles tendon loading. However, injury risk associated with AFT use remains equivocal, with limited high-quality data. Notably, substantial inter-individual variability has been observed, influencing both running economy and potential injury risk although the determinants of this variability remain unclear.