Abstract
Tibial stress fractures are among the most common and potentially serious overuse
injuries in runners. The fractures are thought to be related in part, to excessive
loading variables, such as vertical average loading rate (VALR) and vertical instantaneous
loading rate (VILR). Although there are several methods for calculating loading rate
in running, little is known about the differences between the results produced by
these methods. The purpose of this study was to compare 3 previously published methods
of calculating VALR and VILR during running. 9 male participants ran on a treadmill
at 2.5, 3.0, and 3.5 m/s. VALR and VILR were calculated from vertical ground reaction
force using 3 methods that differed by the period over which the loading rates were
calculated; foot strike to first peak (method A), from 20 to 80% of the time to first
peak (method B), and over the first 50 ms after foot strike (method C). There were
significant differences among methods with regard to VALR, but not VILR. Therefore,
the results of the present study suggest that VILR is preferable to VALR for consistent
evaluation among methods, which make it more acceptable to make study comparisons.
Key words
tibial stress fracture - running injury - ground reaction force
