Footwear-specific biomechanical and energetic responses to 8 weeks of training in advanced footwear technology

BackgroundWhile the acute effects of advanced footwear technology (AFT) on running biomechanics and efficiency have been extensively studied, the longitudinal effects of AFT use are unknown. ObjectiveThe purpose of this study was to investigate the effects of using advanced footwear technology (AFT) versus traditional racing flats during running workouts on relative running economy (RE) and energetic cost (EC), and explore associations between changes in footwear-specific biomechanics and performance. MethodsThirteen competitive runners were randomly assigned Nike Vaporfly Next% 3 (VP) or Nike Rival Waffle 5 (FL) for an 8-week intervention and completed pre- (PRE) and post-intervention (POST) lab testing in both shoes. Weekly training data, including mileage, workouts, and soreness, were collected via questionnaires. Subjects ran two 3-min trials at a self-selected cross-country race pace, with sagittal plane ankle and metatarsophalangeal (MTP) joint kinematics and kinetics recorded and analysed. Subsequently, four 5-min trials were completed at a self-reported submaximal pace, in a randomized order, and shoe-specific RE and EC were calculated and reported as "VP% benefit" - the percentage RE or EC improvement in VP versus FL. Pearsons correlations were tested between RE outcomes and exploratory biomechanics measures, and independent samples t-tests tested for group differences in shoe-specific and overall efficiency changes from PRE to POST. ResultsVP% benefit increased from PRE to POST in VP trained runners and decreased in FL trained runners. VP trained runners decreased ankle plantarflexion velocity in VP, increased ankle dorsiflexion velocity in VP, and decreased MTP plantarflexion velocity in FL. Correlations revealed several significant associations between metabolic outcome measures, and biomechanical and training variables. ConclusionsMetabolic data support a footwear specificity of training principle (habituation), where training in VP may enhance a runners ability to benefit from VP on race day. Associations reveal that this may be due to changes in footwear-specific biomechanics at the ankle and MTP joints. Future research should explore the potential mechanisms through which runners adapt to AFT to maximize their performance benefits. Key PointsO_LIThe acute metabolic benefits and reduced mechanical demands in advanced footwear technology (AFT) have previously been demonstrated in distance runners. In an 8-week footwear intervention study, runners who trained in AFT increased their metabolic benefit from AFT and runners who trained in traditional racing flats decreased acute AFT metabolic benefits. C_LIO_LIChanges in ankle and metatarsophalangeal joint mechanics partially explain these changes in AFT metabolic benefits. C_LIO_LIData from this research support the findings of an earlier pilot study and replicate a habituation effect with AFT use during hard effort workouts, suggesting runners may consider using AFT prior to competition to maximize performance benefits. C_LI