Abstract
In this paper we examined how runners with different initial foot strike pattern (FSP) develop their pattern over increasing speeds. The foot strike index (FSI) of 47 runners [66% initially rearfoot strikers (RFS)] was measured in six speeds (2.5–5.0 ms−1), with the hypotheses that the FSI would increase (i.e., move toward the fore of the foot) in RFS strikers, but remain similar in mid- or forefoot strikers (MFS) runners. The majority of runners (77%) maintained their original FSP by increasing speed. However, we detected a significant (16.8%) decrease in the FSI in the MFS group as a function of running speed, showing changes in the running strategy, despite the absence of a shift from one FSP to another. Further, while both groups showed a decrease in contact times, we found a group by speed interaction (p < 0.001) and specifically that this decrease was lower in the MFS group with increasing running speeds. This could have implications in the metabolic energy consumption for MFS-runners, typically measured at low speeds for the assessment of running economy.
Highlights
Foot strike patterns (FSP) describe the location of the first contact area of the foot with the ground (Cavanagh and Lafortune, 1980) during running
In the post hoc analysis, both groups exhibited significantly decreased contact times with increasing velocities [rearfoot strikers (RFS): F(1,5) = 718.4, p < 0.001; mid- or forefoot strikers (MFS): F(1,5) = 244.9, p < 0.001], the interaction indicate a higher decrease of contact time in the RFS group
We examined the effect of speed on the foot strike index (FSI) and contact time for RFS and MFS runners
Summary
Foot strike patterns (FSP) describe the location of the first contact area of the foot with the ground (Cavanagh and Lafortune, 1980) during running. The two strategies provide very distinct running patterns, exhibiting differences in a plethora of biomechanical characteristics (Hayes and Caplan, 2012; de Almeida et al, 2014; Almeida et al, 2015; Strauts et al, 2015; Valenzuela et al, 2015). The common strategy employed by humans to increase speed until ∼7 ms−1 is by exerting larger vertical ground reaction forces (Arampatzis et al, 1999; Weyand et al, 2000), which leads to increments in step length (Mercer et al, 2002; Dorn et al, 2012).
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