Strike type index and strike mode were compared between groups using a non-parametric Wilcoxon test. Effects were considered significant for p < 0.05. All analyses were done using JMP 5.0

(SAS Institute, Cary, NC, USA). The two groups of Tarahumara, summarized in Table 1, did not differ significantly in age, height, leg length, or body mass, although as might be expected, the mean age of the conventionally shod Tarahumara subjects was nearly 8 years below the minimally shod subjects (p = 0.21, t test). Footwear history, however, was very significantly different (p < 0.001, Wilcoxon test). This Gemcitabine reflected the selection criteria used to define the two groups, with minimally shod Tarahumara wearing huaraches almost exclusively, and the less traditional, conventionally shod individuals selleck inhibitor wearing them occasionally or rarely. Very few of the participants reported running barefoot as adults, although some of the minimally shod Tarahumara said they would sometimes take off one or both huaraches for kicking the ball during the rarajipari, and children often run barefoot. Although there is much variation, there were significant differences between the groups in terms of strike types,

as summarized in Table 2. Among the minimally shod Tarahumara, 40% had a modal MFS strike type, 30% had a modal FFS strike type, and 30% had a modal RFS strike type. Among the conventionally shod Tarahumara, 75% had an RFS modal strike type, and 25% had an MFS modal strike type. As Fig. 2A illustrates, this difference was reflected in mean

strike type, which averaged 2.04 for the minimally shod Tarahumara and 2.69 for the conventionally shod Tarahumara reflecting the predominance of MFS landings among the former and RFS landings among the latter (p = 0.045, Wilcoxon test). AOIs ( Table 2) also indicate that the ankle was significantly more dorsiflexed in the conventionally shod versus minimally shod groups (p = 0.04, t test). Speeds used ranged between 2.3 m/s and 4.8 m/s, but as Fig. 2B shows, there many was no significant correlation between speed and AOI for subject averages (r = 0.04; p = 0.83) or for all trials (r = 0.02; p = 0.85), nor did it correlate significantly with other anthropometric variables. Strike type, however, did correlate significantly with step frequency (r = 0.47; p = 0.03, ANOVA), with individuals who used higher step frequencies being more likely to FFS or MFS. Given the high degree of variation within the minimally shod group, which included individuals who used RFS, MFS, and FFS landings, there were not many significant kinematic differences between the groups. Although the conventionally shod Tarahumara had a tendency to have lower preferred step frequencies, neither preferred step frequency nor the step frequency used during the trials differed significantly. Speed also did not differ between the groups.