Author(s): ALDA-BLANCO, A., RODRÍGUEZ-BARBERO, S., MUÑOZ DE LA CRUZ, V., VALERO, F., GONZÁLEZ-MOHÍNO, F., Institution: UNIVERSIDAD DE CASTILLA LA MANCHA, Country: SPAIN, Abstract-ID: 1383

INTRODUCTION:
Running economy (RE) reflects the metabolic energy required to sustain a given running speed. Small improvements in RE translate into meaningful improvements performance [1], enabling athletes to maintain higher speeds or delay the onset of fatigue. As highlighted by Kipp, Kram [1], even marginal metabolic savings accumulate substantially over long‑distance efforts, reinforcing RE as a key determinant of performance and a crucial predictor of fatigue development. A growing body of research that highlights that this determinant progressively deteriorates is known as “durability” [2]. This study aimed to assess the athlete’s durability during a 1-hour effort and their influence on the subsequent graded exercise test (GXT) to exhaustion, comparing two advanced footwear technology (AFT) shoes in trained male runners.
METHODS:
Twelve male trained runners (World Athletics [WA] score: 820.8 ± 107.3 points) performed, in a randomized-counterbalanced design, a GXT until VT1 speed determination, followed by a 1-hour effort at +10% VT1 speed, and lastly a GXT until exhaustion 5min after on two different visits separated by 7-10 days with different AFT shoes (Cloudboom Strike [CS] and Cloudboom Echo 3 [CE]). Metabolic and auto-perceived parameters were monitored throughout.
RESULTS:
Results showed no shoe*time interaction effect was found during the 1-hour effort test, however participants exhibited an increase in heart rate (p<0.001), RPE (p<0.001), and a reduction in respiratory exchange ratio (RER) (p<0.01), carbon dioxide production (p<0.05), and a shift in substrate utilization from carbohydrate oxidation to fat oxidation (p<0.05), irrespective of the shoe model. During the GXT, participants using CS condition achieved higher peak speed (p<0.05) and higher VT2 speed (p<0.05) compared to the CE, also lower RER was achieved at VT2 with CS (p<0.05)
CONCLUSION:
Under submaximal and metabolically steady conditions, the similarities between shoe conditions may have outweighed the mechanical differences, explaining the absence of changes in physiological drift or metabolic cost. In contrast to the prolonged run, footwear differences emerged during the fatigued‑state GXT, where participants had higher peak velocity and higher VT2 velocity when using CS than using CE. The lower compression stiffness and the 15 g mass difference between conditions might have helped with the differences between shoe conditions. Independent of shoe condition, a 1-hour effort at +10% VT1 speed increases cardiovascular strain and RPE, with an increase in fat oxidation.

1. Kipp, S., R. Kram, and W. Hoogkamer, Extrapolating Metabolic Savings in Running: Implications for Performance Predictions. Front Physiol, 2019. 10: p. 79.
2. Jones, A.M., The fourth dimension: physiological resilience as an independent determinant of endurance exercise performance. The Journal of Physiology, 2024. 602(17): p. 4113-4128.