Reliability, Reproducibility, and Individual Responses of Running Economy Measures in Different Advanced Footwear Technology Shoes

PURPOSE: This study aimed to evaluate the reliability and reproducibility of running economy measurements across multiple days and within the same day using 2 models of advanced footwear technology. METHODS: Thirteen trained male runners (age: 27.6 [8.2] y; body mass: 64.4 [6.1] kg; height: 1.74 [0.06] m) completed 4 treadmill sessions separated by 7 days. Two advanced footwear technology models were tested in a randomized crossover design. Each session included two 5-minute trials per shoe condition at 13 km·h-1. Reliability and reproducibility of running economy measures were evaluated using intraclass correlation coefficients (ICCs), SEM, coefficient of variation, and smallest worthwhile change. RESULTS: Intrasession ICCs and coefficient of variations for oxygen cost and metabolic cost were excellent for both shoe conditions (.917 and .945; .921 and .948; ∼1%). Intersession reliability was good (oxygen cost ICC = .819; metabolic cost ICC = .849), though coefficient of variations increased (∼2%). No significant differences in metabolic variables were observed between footwear models (P ≥ .05), and high variability was observed between individuals. Day-to-day variability affected oxygen cost and metabolic cost (P < .05), independent of shoe condition. CONCLUSION: Running economy measurements are highly reliable within sessions but demonstrate moderate variability across days. Despite mechanical differences in footwear conditions, no differences were observed between the 2 models. These findings highlight the importance of multitrial, multiday, and individual testing when evaluating footwear conditions.