Influence of Running Shoe Longitudinal Bending Stiffness on Running Economy and Performance in Trained and National Level Runners

Introduction/purpose Previous results about shoe longitudinal bending stiffness (LBS) and running economy (RE) show high variability. This study aimed to assess the effects of shoes with increased LBS on RE and performance in trained and national runners. Methods Twenty-eight male runners were divided into two groups according to their 10-km performance times (trained, 38-45 min and national runners, <34 min). Subjects ran 2 x 3 min (at 9 and 13 km<middle dot>h(-1) for trained, and 13 and 17 km<middle dot>h(-1 )for national runners) with an experimental shoe with carbon fiber plate to increase the LBS (Increased LBS) and a control shoe (without carbon fiber plate). We measured energy cost of running (W<middle dot>kg(-1)) and spatiotemporal parameters in visit one and participants performed a 3000 m time trial (TT) in two successive visits. Results Increased LBS improved RE in the trained group at slow(11.41 +/- 0.93 W<middle dot>kg(-1)vs 11.86 +/- 0.93 W<middle dot>kg(-1)) and fast velocity (15.89 +/- 1.24 W<middle dot>kg(-1)vs 16.39 +/- 1.24 W<middle dot>kg(-1)) and only at the fast velocityin the national group (20.35 +/- 1.45 W<middle dot>kg(-1)vs 20.78 +/- 1.18 W<middle dot>kg(-1)). The improvements in RE were accompanied by different changes in bio-mechanical variables between groups. There were a similar improvement in the 3000 m TT test in Increased LBS for trained (639 +/- 59 vs644 +/- 61 s in control shoes) and national runners (569 +/- 21 vs 574 +/- 21 s in control shoes) with more constant pace in increased LBS comparedwith control shoes in both groups. Conclusions Increasing shoe LBS improved RE at slow and fast velocities in trained runners and only at fast velocity in national runners. However, the 3000 m TT test improved similarly in both levels of runners with increased LBS. The improvements in RE are accompanied by small modifications in running kinematics that could explain the difference between the different levels of runners.