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IS SHOE DROP A KEY FACTOR FOR INJURY PREVENTION IN RUNNING? PART 2: AN RCT ON RUNNING BIOMECHANICS

Background So far, only few biomechanical studies have specifically addressed the acute effect of the heel-to-toe drop in running shoes, but longitudinal studies are lacking. Objective Our aim was to investigate if the drop of conventional cushioned shoes induces specific long-term adaptations in running technique. Design Randomised controlled trial. Setting Leisure-time distance runners were tested on a treadmill at their preferred running speed before and after a 6-month period. Participants Study participants (n=59), unexperienced with minimalist shoes, were recruited via advertisements in local newspapers. Intervention The participants received a pair of running shoes with a drop of 10 mm (D10, n=20), 6 mm (D6, n=17) or 0 mm (D0, n=22). Apart from the shoe drop, the 3 versions were strictly identical. Main Outcome Measurements Kinematic and spatio-temporal variables of running trials were obtained using synchronized systems for three-dimensional motion analysis (200 Hz) and step cycle event detection. Joint angles were investigated at initial contact and mid-stance phase of 151±22 analysed steps per record. Two-way analysis of variance for repeated measures with the post hoc Bonferroni correction was used and accepted significance was set at p<0.05. Results The participants performed on average a total of 332±178 km over 163±16 days between pre- and post-tests. No interaction between shoe drop and time was found for any of the spatio-temporal variables, or for any angles at initial contact. At mid-stance phase, a significant shoe drop by time interaction was found for knee abduction angle (p=0.032). For D0 group, knee abduction decreased (−0.3±3.1 vs. -1.3±2.6°) in contrast to D6 (0.3±2.7 vs. 1.3±3.1°) and D10 (−0.2±3.2 vs. 0.5±3.1°) groups. However, none of the pairwise comparisons was significant in the post-hoc analysis. Conclusions Shoe drop of standard cushioned shoes does not seem to influence long term adaptation in running biomechanics.