Ground contact time GCT was determined quantitatively in Tracker 2 as the time

Ground contact time gct was determined quantitatively

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Ground contact time (GCT) was determined quantitatively in Tracker 2 as the time from initial foot strike to toe-off. 7 GCT was Table 1. Runners’ characteristics Characteristic Mean ± SD or N a Age, y 16.07 ± 1.07 Height, m 1.76 ± 0.04 Weight, kg 61.14 ± 6.48 Weekly mileage 21.86 ± 9.84 5K pace, min:s 18:44 ± 1:08 Training shoe type Traditional N = 9 Minimalist N = 5 Barefoot N = 0 a Data available for 14 of 15 subjects.
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May Jun 2015 Gillinov et al 258 measured 3 times for each footwear trial, and the mean of these 3 measurements was used for comparison. Stride cadence (SC) was measured in Tracker 2 over a 60-second period. Each foot strike throughout the interval was counted, resulting in the number of foot strikes per minute for each type of running footwear. Knee flexion angle at ground contact (KA) was measured using Tracker. 2 Three measurements for KA were determined using the reflective tape placed on the right leg. The supplements of these angles (ie, the acute angle formed with the lower leg and the extension of the upper leg past the knee as sides of the angle) were then calculated and used for analysis. 5 Statistical Analysis Continuous data are expressed as mean ± standard deviation. Kruskal-Wallis 1-way analysis of variance tests were used to analyze group differences for continuous data. Group comparisons were made using chi-square tests (Fisher exact tests if appropriate). Each runner served as his own control. Multivariable polytomous logistic regression analysis was used to determine the factor(s) most associated with group differences. With footwear group as the outcome, all biomechanics variables (foot strike, GCT, SC, and KA) were forced into the model (Appendix 1, available at ). A sample size of 13 runners was necessary to detect a 5% decrease in ground contact time, assuming an average ground contact time in traditional shoes of 270 ± 11 ms (based on preliminary studies), with a 2-sided type 1 error rate = 0.05 and 90% power. All statistical analyses were performed using SAS (version 9.2; SAS Inc). RESULTS Foot Strike Subjects were more likely to use an RFS in traditional shoes (86.7%) than in minimalist shoes (66.7%) or in the socked condition (40%) ( P = 0.03) (Figure 2). Conversely, FFS and MFS were more common in the socked condition (FFS, 27%; MFS, 33%) and minimalist shoes (FFS, 20%; MFS, 13%) than in traditional shoes (FFS, 7%; MFS, 7%) (Figure 2). Ground Contact Time Mean GCT was the longest in traditional shoes, shorter in minimalist shoes, and shortest in the socked condition ( P = 0.005) (Figure 3). There was no statistical difference between GCT in minimalist shoes and the socked condition, Figure 1. Still frames capturing 3 foot strikes used to determine type of foot strike at ground contact: (a) forefoot strike in socked condition, (b) midfoot strike in minimalist shoes, and (c) rearfoot strike in traditional shoes.
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  • Fall '15
  • Dr. Wiersma

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