Author(s): CEDRO, E., BELTRAMI, F., SPENGLER, C., Institution: ETHZ, Country: SWITZERLAND, Abstract-ID: 2197

INTRODUCTION:
The interaction of a runner with footwear from the early familiarization period to long-term wear are still not fully understood. Shoe characteristics such as foam type and hardness may play key roles in the interplay between athlete and footwear during familiarization and long-term use. This study assessed how running economy, gait and perceived comfort evolved when runners used two identical shoes differing only in the hardness of the midsole foam.
METHODS:
Fourteen healthy males (age: 30 ± 4 years, weight: 73 ± 6 kg, height: 181 ± 3 cm, V̇O2peak: 56.0 ± 16.9 ml∙kg-1∙min-1) took part in this longitudinal study. Participants were given a pair of soft (SS, Shore C Hardness 45, energy return [ER] 6.4 J) and hard (HS, Shore C Hardness 70, ER 5.7 J) shoes to alternate in use during training. They visited the laboratory for assessments of running economy, spatiotemporal and perceptual variables at four different points of shoe mileage (0 km, 30–50 km, 150–200 km and 250-300 km, the latter performed by n = 8 participants). Tests consisted of three 5-min runs in each shoe condition with 2-min break inbetween, in randomized, balanced order, while assessing gas exchange, spatiotemporal, and perceptual variables. At the last visit, both pairs of old shoes were randomly rotated with a new pair of shoes.
RESULTS:
In the SS, V̇O₂ was 1.4–2.3% lower than in the HS across all visits (all p < 0.03) while no longitudinal changes were observed and no difference observed between old and new shoes in the last visit. HR was 1.2–2.1 bpm lower in the SS compared with the HS at visits 1 and 2 (both p < 0.02), with no detectable differences thereafter. The SS was also associated with greater comfort, with 17-26 points higher (0–100 VAS scale) than the HS, across all visits (all p < 0.04). From visit 1 to 3, HR decreased in both the SS (-6.3 ± 2.2 bpm; p = 0.01) and the HS (-6.9 ± 2.5 bpm; p = 0.02). Comfort decreased across the first 3 visits in the HS only while remaining unchanged in the SS. Changes in gait variables were minimal between shoe conditions and over time.
CONCLUSION:
The softer foam improved running economy and perceived comfort during the entire distance of 300 km with no visible divergent effects of shoe degradation over this mileage, and with only minimal changes in spatiotemporal variables. Since no noticeable detrimental effects of footwear wear were detected up to 300 km with both soft and hard shoe models, the footwear can be considered reliable for competition and testing up to this distance. Potential benefits of footwear familiarization were either not present or were quickly cancelled out by very early foam degradation. As physiological variables remained stable up to 300 km of wear while comfort decreased substantially for the HS model, perceived comfort seems to play no role in modulating running economy.