7 Unlike Kalenjin adults that grew up barefoot, habitually barefoot Kalenjin adolescents, and habitually barefoot U.S. adults, Hadza runners never used FFS in trials recorded for this study. Due to the mix of MFS and RFS among the Hadza, mean plantar foot strike angle among adults was intermediate between selleck chemicals llc habitually

shod U.S. adults and Kalenjins. U.S. adults ran with a high frequency of RFS, thus leading to the large dorsiflexion upon plantar foot strike, causing smaller (negative) foot angles. Kalenjins had a high frequency of FFS, thus showing the large plantarflexion upon foot strike and larger angles. Ankle angles among Hadza adults were similar to those of habitually barefoot U.S. adults, barefoot Kalenjin adolescents, and Kalenjin adults who grew up

barefoot. Knee angles at foot strike were consistently greater (i.e., more flexed) among Hadza adults than for Kalenjin or U.S. groups. The difference in knee Selleckchem MK2206 angle is more substantial when differences in running speed are considered; Hadza speeds were lower, on average, than those of the Kalenjin or U.S. groups reported by Lieberman and colleagues,6 yet knee flexion generally increased with speed in our sample. Direct comparison of joint angles among studies is hampered by the different methods used to measure them. Unlike Lieberman and colleagues,6 we did not place visual markers on anatomical landmarks. Instead, the knee angle in our study was calculated using the major axes of the thigh and shank, which may have resulted in systematic differences in knee angle calculation relative to the analysis of Lieberman and colleagues. The image resolution and lack of visual markers probably also decreased the precision of our angle measurements, an effect that was most evident in our inability MRIP to distinguish plantar angles ±1° for MFS trials (Fig. 2). Thus, while we took care to calculate angles in a manner that would maximize comparability to other studies (Fig. 1), it is possible that some differences between

studies arise from methodological differences. Foot strike behavior among traditional Hadza hunter-gatherers was mixed, with consistent differences between men and women and between juveniles and adults. Women and juveniles used RFS more often than MFS, while men used MFS almost exclusively. There was no difference between shod versus barefoot conditions, nor among respirometry trials (which lasted for several minutes) and short-bout trials (which lasted a few seconds). The lack of difference between short-bout and respirometry trials lends confidence that the duration of the trial did not affect foot strike choice. Further, there is no evidence that Hadza adults switched from RFS to MFS as speed increased. While the Hadza used MFS rather than FFS, comparisons with other populations suggest that Hadza men are similar to experienced barefoot runners such as the Kalenjin in avoiding RFS.