Does heel-toe drop of normal stack height shoes affect vertical loading rates, footstrike pattern and temporal spatial parameters in runners?

![CDATA[Rationale/Objectives: Heel-toe drop, which is defined as the height difference between fore and rear parts of the midsole, is a common feature to be adjusted in running shoe design. Previous studies have proposed heel-toe drop can affect running biomechanics. However, most previous studies used minimalists to test the effect of heel-toe drop. Therefore, we sought to examine the effect of heel-toe drop of normal stack height shoes on vertical loading rates, footstrike pattern and temporal spatial parameters in the present study. Methods: Fifteen habitual rearfoot strikers were recruited from local running clubs. They were asked to run on an instrumented treadmill in four shod conditions i.e. normal stack height (21-mm) shoes with different heel-toe drop (0, 4, 8 and 12 mm) in a randomized sequence. We compared the average and instantaneous loading rates (VALR and VILR), footstrike angle (FSA), temporal spatial parameters (i.e., contact time, cadence, and stride length) and comfort between the four shod conditions. Results: Heel-toe drop exhibited significant effect on FSA (p<0.001) stride length (p=0.005) and cadence (p=0.015) but not significant for VALR (p=0.125), VILR (p=0.152), contact time (p=0.198) and comfort (p=0.146). Pairwise comparisons only showed that shoes with <4-mm heel-toe drop resulted in a reduction of FSA than shoes with greater heel-toe drop (p<0.034), but the change was insufficient to cause a footstrike pattern switch.]]