Comparison of 3 Methods for Computing Loading Rate during Running.

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.

Step Frequency and Step Length of 200-m Sprint in Able-bodied and Amputee Sprinters.

The goal of this study was to examine the hypothesis that the difference in the 200-m sprint performance of amputee and able-bodied sprinters is due to a shorter step length rather than a lower step frequency. Men's elite-level 200-m races with a total of 16 able-bodied, 13 unilateral transtibial, 5 bilateral transtibial, and 16 unilateral transfemoral amputee sprinters were analyzed from publicly available internet broadcasts. For each run, the average forward velocity, step frequency, and step length over the entire 200-m distance were analyzed for each sprinter. The average forward velocity of able-bodied sprinters was faster than that of the other 3 groups, but there was no significant difference in average step frequency between able-bodied and transtibial amputee sprinters. However, the average step length of able-bodied sprinters was significantly longer than that of the transtibial amputee sprinters. In contrast, the step frequency and step length of transfemoral amputees were significantly lower and shorter than those of the other 3 groups. These results suggest that the differences in 200-m sprint performance between able-bodied and amputee sprinters are dependent on amputation level.