Abstract
Endurance running may have a long evolutionary history in the hominin clade but it was not until very recently that humans ran wearing shoes. Research on modern habitually unshod runners has suggested that they utilize a different biomechanical strategy than runners who wear shoes, namely that barefoot runners typically use a forefoot strike in order to avoid generating the high impact forces that would be experienced if they were to strike the ground with their heels first. This finding suggests that our habitually unshod ancestors may have run in a similar way. However, this research was conducted on a single population and we know little about variation in running form among habitually barefoot people, including the effects of running speed, which has been shown to affect strike patterns in shod runners. Here, we present the results of our investigation into the selection of running foot strike patterns among another modern habitually unshod group, the Daasanach of northern Kenya. Data were collected from 38 consenting adults as they ran along a trackway with a plantar pressure pad placed midway along its length. Subjects ran at self-selected endurance running and sprinting speeds. Our data support the hypothesis that a forefoot strike reduces the magnitude of impact loading, but the majority of subjects instead used a rearfoot strike at endurance running speeds. Their percentages of midfoot and forefoot strikes increased significantly with speed. These results indicate that not all habitually barefoot people prefer running with a forefoot strike, and suggest that other factors such as running speed, training level, substrate mechanical properties, running distance, and running frequency, influence the selection of foot strike patterns.
Highlights
Among mammals, humans are adept at running for long distances
While cushioning in modern running shoes helps mitigate the effects of these forces and allows people to land on their heels, the authors pointed out that barefoot runners who use a Rearfoot strike (RFS) may be at greater risk of injury or discomfort
The incidence of a forefoot strikes (FFS) was greatest at running speeds between 5.01 and 6.00 m/s (14% of trials) but this running style was never used by the majority of our subjects at any speed
Summary
Humans are adept at running for long distances. Certain human ancestors may have used their cursorial abilities for hunting (e.g., persistence hunting) in order to gain access to high-quality foods and reap a competitive advantage over other animals [1]. While cushioning in modern running shoes helps mitigate the effects of these forces and allows (or even encourages) people to land on their heels, the authors pointed out that barefoot runners who use a RFS may be at greater risk of injury or discomfort They argued that habitually unshod runners utilize a different biomechanical strategy than people who run in shoes – barefoot runners more often strike the ground with their forefoot or midfoot first, thereby reducing impact peaks, while shod runners tend to land on their heels. Nigg and colleagues [21] showed that when habitually shod runners increase speed, they alter the position of their foot at strike in order to cope with the higher collision forces associated with that greater speed This hypothesis was supported by Keller and colleagues [22], who reported that habitually shod runners who used predominantly a RFS when running at speeds 5 m/s or slower, preferred a FFS at 6 m/s or faster. In light of previous research [21,22] that associated changes in strike patterns with changes in running speed, we explored the alternate but not mutually exclusive hypothesis that strike patterns in habitually unshod runners are influenced by speed, with higher incidence of forefoot striking at higher speeds
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