Effects of heel-toe drop on running biomechanics and perceived comfort of rearfoot strikers in standard cushioned running shoes

Effects of heel-toe drop, which is the height difference between the rearfoot and forefoot parts of the shoe, have been studied during running in minimalist shoe models. However, these types of shoes also feature low heel stack height. Effects of heel-toe drop remain largely unknown during running in cushioned shoes, which usually present a standard heel stack height (e.g. 21 mm). The purpose of this study was to investigate the isolated effect of heel-toe drop on running kinematics and kinetics and perceived footwear comfort of runners in standard cushioned shoes. Fifteen male habitual rearfoot strike runners ran in four shod conditions: no drop (0 mm, D0), 4-mm (D4), 8-mm (D8), and 12-mm drop (D12). Running kinematics and kinetics were collected using motion capturing system and instrumented treadmill, respectively. Footwear comfort was acquired immediately after each running trial using a visual analogue scale. Significant effects were demonstrated on footstrike angle (p < 0.001), stride length (p = 0.005), and cadence (p = 0.015). A greater footstrike angle was indicated during running in D8 compared with D4 (p = 0.034) and D0 (p = 0.006). However, such reduction was not sufficient to cause footstrike pattern transition towards a midfoot/forefoot strike pattern. Stride length in D8 was significantly larger than in D12 (p = 0.007). No significances were found on vertical loading rates, contact time and perceived footwear comfort (p > 0.05). The isolated effects of heel-toe drop on running biomechanics were demonstrated in shoe models with a standard heel stack height. A lower heel-toe drop of standard cushioned shoes may reduce footstrike angle and increase stride length during running.