Author(s): GONZÁLEZ-MOHÍNO, F., ALDA-BLANCO, A., RODRÍGUEZ-BARBERO, S., MUÑOZ DE LA CRUZ, V., VALERO, F., SALINERO, J.J., Institution: UNIVERSITY OF CASTILLA-LA MANCHA, Country: SPAIN, Abstract-ID: 2005

INTRODUCTION:
Most studies investigating these effects of advanced footwear technology (AFT) have been conducted within a single testing session, usually including two repetitions per footwear conditions because of the errors associated with the metabolic analyzers in running economy (RE) evaluations [1]. While this approach reduces between-day variability, it does not account for normal day-to-day physiological fluctuations, which may be of a similar magnitude to the RE improvements attributed to AFT. Consequently, single-session designs provide limited insight into test–retest reliability and the temporal stability of footwear-related effects. To date, limited evidence exists regarding the reproducibility of RE measurements across multiple days while using different AFT models [2], leaving uncertainty about the stability of these effects over time. In this regard, the study aimed to evaluate the reliability and reproducibility of RE measurements across multiple days and within the same day using two models of AFT.
METHODS:
Thirteen trained male runners (age: 27.6 ± 8.2 years; body mass: 64.4 ± 6.1 kg; height: 1.74 ± 0.06 m) completed four treadmill sessions separated by 7 days. Two AFT models were tested in a randomized crossover design. Each session included two 5-min trials per shoe condition at 13 km·h-1. Reliability and reproducibility of RE measures were evaluated using intraclass correlation coefficients (ICC), standard error of measurement, coefficient of variation (CV), and smallest worthwhile change.
RESULTS:
Intra-session ICCs and CVs for oxygen cost and metabolic cost were excellent for both shoe conditions (0.917 and 0.945; 0.921 and 0.948; ~1%). Inter-session reliability was good (oxygen cost ICC = 0.819; metabolic cost ICC = 0.849), though CVs increased (~2%). No significant differences in metabolic variables were observed between footwear models (p ≥ 0.05) and high variability was observed between individuals. Day-to-day variability affected oxygen cost and metabolic cost (p < 0.05), independent of shoe condition.
CONCLUSION:
RE measurements are highly reliable within sessions but demonstrate moderate variability across days. Despite mechanical differences in footwear conditions, no differences were observed between the two models. These findings highlight the importance of multi-trial, multi-day, and individual testing when evaluating footwear conditions.

REFERENCES
1. Barrons, Z.B., et al., The Fallacy of Single Trials: The Need for Multiple Trials in Assessing Running Economy Responses in Advanced Footwear Technology. Sports Medicine, 2024. 54(6): p. 1357-1360.
2. Nielsen, A., et al., Reliability of Running Economy Measurements: Influence of Shoe Familiarisation. International Journal of Sports Medicine, 2022. 43(13): p. 1113-1117.