## 2 Materials and Methods
### Procedures and Measurements  
The experimental protocol consisted of two trials (cushioned shoe vs. minimalist-control shoe) and three condition walk-run treadmill speeds (6, 10, and 14 km\(\cdot\)h\({}^{-1}\)) that were typically used by the participants in their everyday running shoe. These speeds have also been shown to produce significant differences in vertical ground reaction forces [12]. Each trial was performed in one session on the same day, performed in a counter-balanced order of shoe conditions, and separated by 15 min to minimise the sequence effect on the dependent variables of interest. Upon arrival at the laboratory, the participants were measured, weighed, and had their footwear size determined for each foot (Figure 1) by a shoe specialist to ensure best fit based on participant input and expertise. The mean (range) in a United States women's size was 8.5 (7.5-9.5) for the cushioned shoe and 8 (6-10) for the non-cushioned shoe. Figure 1B shows the cushioned shoe (Asics Gel-Nimbus 25, Asics Corporation, Kobe, Japan), which had a 40.5 mm heel and a 32.5 mm forefoot (8 mm drop) midsole featuring a single layer of FlyteFoam BLASTTM ECO Plus foam cushioning with an extra PureGELTM insert in the rearfoot, and had a rocker (manu  
Figure 1: Photographic representation of (**A**) the minimalist shoe and (**B**) the cushioned shoe. version 0.9.5 [47]) angle of 15\({}^{\circ}\), rocker radius of 45\({}^{\circ}\), apex position of 70%, apex angle of 75\({}^{\circ}\), and a weight of 235 \(\pm\) 9 g. The midsole hardness scale C, measured with a durometer (HC), was 30.1 \(\pm\) 0.1 HC. Figure 1A shows the minimalist shoe [48], which had a 0 mm heel-toe drop, a 5 mm PVC rubber outside (H&S, The Warehouse, Auckland, New Zealand), and weighed 206 \(\pm\) 14 g, with a midsole durometer reading of 55.0 \(\pm\) 6.1 HC. Trial order was selected, and the appropriate footwear was fitted with a flexible pressure inside to record kinetic data (LoadSol(r) Pro, Novel GmbH, Munich, Germany), whereupon each insole (left and right) was configured for the specific participant and followed the manufacturer's bipedal calibration process. Each trial consisted of a 5 min warm-up period on the treadmill (Life Fitness, Hamilton, New Zealand) at the participant's preferred running speed. Each condition (shoe*speed) was performed for a period of 1 min, with data logged throughout and analysed during the last 10 s of each condition [49]. The participants were blind to any dependent variables being measured. LoadSol(r) time*force data (200 Hz) were uploaded into MATLAB (R202b, MathWorks, Inc., Natick, MA, USA), re-sampled to 1000 Hz, and processed using force threshold values of 20-30 N to determine the initial foot contact and toe-off [50]. From these outputs, the following dependent variables were calculated using techniques previously described for walking [51] and running [52] and expressed per body weight (N) where appropriate: (a) Peak vertical impact force (N\(\cdot\)BW\({}^{-1}\)), identified as the first peak between initial contact and the active peak. If the first peak was not present in running (mid-forefoot strike), it was defined as the force at 13% of the stance phase; (b) Active peak vertical force (N\(\cdot\)BW\({}^{-1}\)), which was the second peak for walkers and heel strike runners, or the highest force reading of each step for mid-forefoot strikers. In running, this point (mid-stance) was described where the foot was directly below the centre of mass.