Running economy and biomechanics throughout the life cycle of a new shoe: Evaluation during a half-marathon 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 and C 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 and C 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). Used in exposures B and C 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 for two 6 min treadmill bouts before and after the half-marathon run in exposure C. 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: Participants will be instructed to progressively incorporate their attributed shoe (AFT or ENER or SFT) in their running training. Participants will be asked to train with it for 150 km following a progressive running training plan. 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. 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. Exposure C: After 150 km of training with the shoe, participants will do a half-marathon treadmill run with their allocated shoe at one of the University of Waikato laboratories. 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. 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. Session will be administered and supervised by the lead investigator.