Transfer of the learning effect in outdoor conditions with varied surface inclinations upon completion of an indoor gait retraining program

![CDATA[Rational & Objective Running retraining using kinetic biofeedback (e.g., tibial shock) has been shown to be effective in impact loading control and injury prevention. Previous training program was usually conducted indoor to enable continuous feedback of peak tibial shock. However, it is not known if the training could benefit running in outdoor conditions across various surface inclinations (e.g., uphill or downhill). This study aimed to compare the reduction in peak tibial shock following running retraining during indoor and outdoor running across varying surface inclinations. Methods Fourteen runners underwent a running retraining program as described by Crowell and Davis in 2011. Before and after the program, participants were asked to perform indoor treadmill running and outdoor overground running at three inclination surfaces (level, 10% uphill and - 10% downhill). During all the six conditions, their peak acceleration from right distal tibia were measured using wireless accelerometers. Results The effect of training depended on running environment (F(1,13) = 11.179, p = 0.005) as well as surface inclinations (F(2,13) = 4.322, p = 0.024). During indoor running, participants managed to reduce the peak tibial shock during level and downhill running (p < 0.003, Cohen’s d = 1.08-1.99), but not in uphill running (p = 0.07, Cohen’s d = 0.513). During outdoor running, participants did not show a reduction in peak tibial shock after the running retraining (p > 0.137, Cohen’s d = 0.32-0.47). Conclusions The learning effect of the current running gait retraining program may not transfer to a reduced peak tibial shock during various inclination surfaces and outdoor running conditions.]]