Runners with lower dynamic stability exhibit better running economy: Results from a randomized crossover study of trained runners across various running speeds and footwear conditions

Background Dynamic stability has been proposed as a factor influencing running economy, but the nature and strength of this relationship remain poorly understood. Further, advanced footwear technology (AFT) has been widely adopted as it improves running economy, but it may also compromise dynamic stability due to its compliant midsole. Understanding the relationship between dynamic stability and running economy and how both can be affected through footwear could have important implications for performance optimization and footwear design. Methods 21 trained runners completed treadmill trials in four AFT models and their habitual SFT shoes at three individualized speeds. Local dynamic stability (LDS) was quantified via maximum Lyapunov exponents from seven segmental angular velocities, aggregated per trial. Running economy was measured as cost of transport. Linear mixed-effects models were used to assess relationships between LDS, COT, and footwear. Results Aggregated LDS was negatively associated with COT ( p =  0.036), indicating that runners with lower dynamic stability had better running economy. Further, footwear condition had no significant effect on LDS ( p =  0.060–0.359), suggesting that AFT does not compromise running stability compared to habitual SFT running shoes. Conclusions This study is the first to demonstrate that an aggregate of LDS across multiple body segments is negatively associated with COT, indicating that runners with lower dynamic stability exhibit better running economy. AFT did not affect LDS compared to habitual SFT, suggesting that alterations of footwear characteristics within commercially available models have limited effects on running stability.