Introduction
The use of tibial acceleration as an indirect measure of impact loading in runners has seen an escalating interest within the research community. This surge in focus is primarily due to the inherent potential of such a metric to predict and understand the physical demands placed on runners and the possible consequences. Specifically, elevated levels of tibial acceleration have been implicated in the genesis of certain running-related injuries, most notably tibial stress fractures. Therefore, this measure has been increasingly employed as a key parameter within clinical surveillance. Guided by this context, the present study was designed to examine and compare the effectiveness of various insoles and foot orthoses in mitigating tibial acceleration, thereby potentially reducing injury risk among runners.
Experimental Design
The experimental protocol entailed the attachment of an accelerometer to the tibia of the participant to obtain acceleration data along the x, y, and z axes, with the 'ay' value being of primary interest. The study was methodically designed to incorporate a range of variables, consisting of five separate tests with two distinctive types of footwear and two different insoles. Data from the barefoot condition served as the control.
Footwear selected for the study included Vans and Reeboks, in addition to a condition with no shoes. Insoles and foot orthoses under investigation encompassed the stock insoles in both the Vans and Reeboks, as well as an aftermarket product known as inStrydes.
The tests were conducted under the following conditions: barefoot, wearing Reeboks with their stock insoles, wearing Reeboks with inStrydes, wearing Vans with their stock insoles, and wearing Vans with inStrydes.
For each test, the participant was asked to walk for a period of five minutes around a designated course on a concrete surface. The accelerometer, affixed to the participant's tibia, consistently recorded acceleration data throughout the duration of each walking session.
Data Acquisition
Data was collected, logged, and subsequently compared to the baseline data obtained from the barefoot condition. Over one million data points were gathered and processed in this study.
Discussion
The maximum tibial acceleration recorded in the control condition was 18.58 m/s^2.
Reeboks: Default insoles presented a 29.76% reduction in tibial acceleration relative to the control. inStrydes insoles resulted in a 31.97% decrease compared to the control.
Vans: Default insoles indicated a 29.92% decrease in tibial acceleration compared to the control, whereas the inStrydes insoles led to a reduction of 28.90%.
Conclusion
All evaluated insoles yielded a decrease in tibial acceleration, presumably contributing to a diminished risk of lower leg injuries. The most significant improvement was noted when the inStrydes were utilized in the Reeboks, reducing tibial acceleration by an additional 2.21% when compared to the other insoles and foot orthoses examined in this study
Citations
Radin, E. L., Parker, H. G., Pugh, J. W., Steinberg, R. S., Paul, I. L., & Rose, R. M. (1983). Response of joints to impact loading—III. Relationship between trabecular microfractures and cartilage degeneration. Journal of biomechanics, 16(7), 517-525.
