Running economy and biomechanics throughout the life cycle of new shoes: Evaluation over the training process in recreational and trained runners.

Intervention shoe 1: Advanced footwear technology (AFT) running shoe Salomon S/Lab phantasm 3 (Mass: 176 g; Heel stack: 39 mm; Forefoot stack: 33 mm; Drop: 6 mm; Shore Asker C: 38; Foam: polyether block amide). It integrates all required characteristics that define an AFT (i.e., curved longitudinal architecture [mostly through a carbon plate], embedded within a highly resilient, compliant, and lightweight midsole foam). Used in exposures B to F by 1/3 of the participants. Intervention shoe 2: Novel advanced footwear technology (ENER) running shoe Salomon prototype (Mass: 290 g; Heel stack: 50 mm; Forefoot stack: 42 mm; Drop: 8 mm; Shore Asker C: 38; Foam: thermoplastic polyurethane). It focuses on foam usage optimisation and shoe geometry, without the use of a rigid longitudinal element. Used in exposures B to F by 1/3 of the participants. Comparator shoe 1: Standard footwear technology (SFT) running shoe Salomon Aero Glide 4 (Mass: 245 g; Heel stack: 38 mm; Forefoot stack: 30 mm; Drop: 8 mm; Shore Asker C: 38; Foam: thermoplastic polyurethane). It is the reference shoe to which the interventions 1 and 2 will be compared. Used in exposures B to F by 1/3 of the participants. Comparator shoe 2: New version of the shoe participants are attributed to. The shoe model and characteristics are the same as detailed previously for AFT, ENER, or SFT. It will be used in exposure D to F to assess the effect of shoe wear and the presence of a learning effect. Exposure A: During a separate preliminary session, participants will complete an incremental treadmill run aiming to determine their maximal aerobic speed. Wearing their own shoes, starting speed will be set depending on participants' 10 km race time. Speed will be increased by 0.5 km/h every minute until voluntary exhaustion. Participants will be randomly attributed to one of the three groups (AFT or ENER or SFT) by the lead investigator (PhD student in sport biomechanics), and will receive the shoe in person. Exposure B: With a between-session gap of at least 72 h, participants will complete two sets of 4 x 6 min treadmill running bouts at one of the University of Waikato laboratories. For each set, they will complete two bouts with the control shoe, and two bouts with their allocated shoe (AFT or ENER or SFT). Between the two sets, participants will run 15 min with their allocated shoe. Exposure C: Participants will be asked to train with their allocated shoe for 300 km following a progressive running training plan corresponding to approximately four months. Training sessions range from 15 min to 120 min, and from 2 to 8 on a rate of perceived exertion scale from 1 to 10. Participants will do five to six sessions a week, for 10 to 12 weeks. They will train at their usual training place. Adherence to training will be assessed by the lead investigator via weekly questionnaires and sharing of GPS-based running data. Training plan details are available in supporting documents. If participants have their own structured programmes or time constraints that prevent them from implementing the recommended training plan, they can continue using their usual training plans as long as the ratio between use of their allocated shoe and own shoe, and/or weekly running times are respected. Participants will return three additional times to the laboratory to run on a treadmill with their allocated shoe, corresponding to measurements after 50, 150, and 300 km of training with their allocated shoe: Exposure D: After 50 km of training with their allocated shoe, participants will run two 6 min treadmill bouts with their allocated shoe and two 6 min bouts with the control shoe. Exposure E: After 150 km of training with their allocated shoe, participants will run a half-marathon treadmill run with it. Before the half-marathon, participants will run two 6 min bouts with their allocated shoe, two bouts with a new version of their allocated shoe (Comparator shoe 2), and two bouts with the control shoe. After the half-marathon, participants will run two 6 min bouts with a new version of their allocated shoe (Comparator shoe 2) and two bouts with the control shoe. Exposure F: After 300 km of training with their allocated shoe, participants will run two 6 min treadmill bouts with their allocated shoe and two 6 min bouts with the control shoe. For Exposures B and D to F: All treadmill runs will be performed at 70% of participants' maximal aerobic speed, except for the half-marathon that will be run at a self-selected race pace, and at 70% of maximal aerobic speed for 6 min intervals every 5 km. All Exposures will be administered and supervised by the lead investigator.